CROSS REFERENCE TO RELATED APPLICATIONS

}M0!| This application claims the benefit of and priority to: U.S. Provisional

Application No. 62/197,510 entitled "Visual Inertial Odometry Attitude Drift

Calibration" filed July 27, 2015, U.S. Provisional Application No.: 62/304,062 entitled "Visual Inertial Odometry Attitude Drift Calibration" filed March 4, 2016. and U. S. Non-Provisional Application. No. 15/078,862 filed March 23, 2016 entitled "Visual Inertial Odometry Attitude Drift Calibration". The above applications are all assigned to the assignee hereof and incorporated by reference, in their entireties, herein,

FIELD

{Θ0Θ2 j The subject matter disclosed herein relates generally to terrestrial positioning systems, and in particular, to systems and methods for attitude and

displacement drift calibration of systems using visual inertial odometry (ViO),

BACKGROUND

[00 31 Advanced Driver Assistance Systems (ADAS) mapping and/or navigation systems may use a point cloud of Light Detection And Ranging (LIDAR.) measurements in a 360 degrees horizontal pattern around the vehicle, which is correlated with a previously obtained high accuracy gcoreferenced texture map. As one example, many ADAS demand absolute accuracy levels in the ra ge of 1 meter or less and relative accuracy (e.g. between two successive positions in a time period) in the decimeter range. Therefore, to maintain accuracy levels, the maps are often frequently updated

|0004| With Global Navigation Satellite Systems (G SS) based trap ing and/or navigation systems, ONSS accuracy may degrade significantly in urban canyons, where m hipath effects may induce an absolute position error of the order of tens of meters (e.g. as much as 50 meters) and relative position error of the order several meters. In addition, accuracy may be further degraded by the limited availability of good G SS measurements. For example, with GNSS measurements that use carrier phase, to achieve higher accuracy, positioning accuracy is dependent on a constant lock obtained by maintaining a clear view to at least four satellites, which may not be possible due to environmental conditions - (eg; in urban canyons). Farther, accurate G SS positioning also relies on the presence of a nearby reference receiver, which may not be available in many situations. In instances where aecelerometer or iMU based inertia] systems are used iricrtiai sensor drift and other biases prevent reliable and accurate position determination.

SUMMARY

{0005.] In some embodiments, a method on a user equipment (UE) ma comprise; determining a first absolute position of the UE at a first time (tl ) based on GN SS meas urements from a set of satellites at the first time (tl ); determining, at a second time (t2), a first estimate of displacement of the UE relative to tine first absolute position, wherein the second lime (ΐ2) is subsequent to the first time (tl ), wherein the first estimate of displacement is determined using non-GNSS measurements; and determining, at the second time (t2), a second estimate of displacement of the LIE relative to the first absolute position based, in part, on: GNSS carrier phase

tneasnrements at the first time (tl) from the set of satellites, and GNSS carrier phase tneasnrements at the second time (t2) from a subset comprising two or more satellites of the set of satelli tes, and the first estimate of displacement of the UE.

{ ^' 0006] In another aspect, a User Equipment (UE) may comprise: a GNSS receiver capable of performing GNSS measurements; at least one non-GNSS displacement sensor to determine UB displacement; a memory to store the GNSS measurements and the non-GNSS displacement sensor measurements; and a processor coupled to the GNSS receiver and the non-GNSS displacement sensor, in some embodiments, the processor may be configured to: determine a first absolute position of the UE at a first lime (tl) based on GNSS measurements from a set of satellites at the first lime (tl); determine, at a second time (t2), a first estimate of displacement of the UB relative to the first absolute position, wherein the second time (t2) is subsequent to the first time (tl), wherein the first estimate of displacement is determined using non- GNSS measurements from the at least one non-GNSS displacement sensor; and determine, at the second time (t2>, a second estimate of displacement of the UB relative to the first absolute position based, in part,, on: GNSS carrier phase

measurements at the first time (tl) from the set of satellites, and GNSS carrier phase measurements at the seeoftd time (t2) from a subset comprising two or more satellites of the set of satellites, and the first estimate of displacement of the UE,

(9007! In a further aspect, a User Equipment (UE) ma comprise: GNSS receiving means capable of performing GNSS measurements; at least one non-GNSS displacemen sensing means to determine UE displacement; means for determining a first absolute position of the UE at a first time ( l } based on GNSS measurements from a set of satellites at the first time (tl ); means for determining, at a second time Ct2), a ^' first -estimate of displacement of the UE relative to the first absolute position, wherein the second time (12) is subsequent to the first time (tl), wherein the first estimate of displacement is determined using non-GNSS measurements determined by the non-GNSS displacement sensing means; and means for determining, at the second time (ΐ2), a second estimate of displacement of the U E relative to the first ^' bsolute position based, in part, on; GNSS carrier phase measurements at the first time (tl ) from the set of satellites,, and GNSS carrier phase measurements at the second time (t2) from, a subset comprising two or more satellites of the set of satellites, and the first estimate of displacement of the UE.

(9008! In another aspect, a non-transitory computer readable medium may comprise instructions, which when executed by a processor, cause the processor to; determine a first absolute position of a User Equipment (UE) at a first time (tl) based on GNSS measurements from a set of satellites at the first time (tl); determine, at a second time (t2), a first estimate of displacement of the UE relative to the first absolute position, wherein the second time (t2) is subsequent to fee first time (tl), wherein the first estimate of displacement is determined using non-GNSS measurements; and determine, at the second time (t2), a second estimate of displacement of the UE relative to the first absolu te position based, in part, on: GNSS carrier phase

measurements at the first time (tl ) from the set of satellites, and GNSS carrier phase measurements at the second time (t2) from a subset comprising two or more satellites of the set of satellites, and the first estimate of displacement of the UE,

(900$! The methods disclosed may be performed by UE, including mobile stations, mobile devices, etc. using a combination of GNSS signals, including carrier phase measurements. Visual Inertia! Odometry and. i conjunction with terrestrial wireless systems, including LPP, LPPe, or other protocols. Embodiments disclosed also relate to software, firmware, arid program instructions .created, stored, accessed, read, or modified by processors using «o¾ transitory computer readable media or ^' computer readable memory.

BRIEF DESCRIPTION OF THE DRAWINGS

{ ^' 0010] FIG. 1 shows a schematic block diagram illustrating certain exemplar features of an UE enabled to support position determination in accordance with disclosed embodiments.

}0: 11| FIG..2 shows an architecture of a system capable of providing Location, and or Navigation services to UEs including, the transfer of location assistance dat or location information.

J0012f Fig, 3A shows an example skyplot of eight GNSS Satellite Vehicles at a point in time.

{0015] Fig, 3B shows a map ofaa exemplary urban environment with UE 100 and some GNSS Satellite Vehicles.

{0014) Fig, 4 shows traditional carrier phase measurements and exemplary hybrid GNSS-VIO carrier phase measurement in accordance with some embodiments disclosed herein.

|Θ01.5| Fig, 5 show -a UE 100 which may be in a vehicle moving from. a.

location PI at time tl to location P2at time t2 along a path..

{00:16] Fig. 6 illustrates an example of single difference carrier phase integer reconstructio / back projection according to some disclosed embodiments.

{0017| Fig. 7 shows that VIO or another non-GNSS positioning estimate of relati ve displacement between points Pi 10 and P2 620 may be used to baek project and resol ve integer ambiguities for SVs 280-1 and 280-2.

{0018] Figs, 8 A and SB show an exemplary method 800 for hybrid GNSS- VIO or hybrid. GNSS - nos-G S S position ^' determination in accordanc with some disclosed embodiments. [0019| Fig. 9 shows an exemplary method 900 for hybrid GNSS - non-CNSS position determination in accordance with some disclosed embodiments

DETAILED DESCRIPTION

[0020) in mapping and/or navigation systems, sack as ADAS (Advanced Driver

Assistance Systems) applications, mapping and/or navigation may use one or more continuous, reliable, and accurate sources of both absolute and relative positioning, ADAS mapping and/or navigation systems may use LIDAR measurements and/or RADAR measurements to obtain relative displacement estimates. The term "relative positioning" or "relative displacement" is used herein to refer to a baseline vector between two positions occupied by a single mapping/navigation entity, such as a single vehicle, or a single user equipment, or a single mobile station over a time period. In some instances, the relative displacement may be expressed in an absolute reference framework, "Relative Positioning" as described above is therefore different from the instantaneous baseline vector between two distinct receivers (e.g. a reference and a rover) at a point in time.

{0021} Some disclosed embodiments pertain to time based relative velocity solution using a GNSS- VIO hybrid approach that combines Visual inertial Odomctry (VIO) with GNSS. The term, "odomctry" refers to the estimation of changes in position over time based on measurements from sensors, in VIO, several visuai features may be tracked from frame to frame, which ma be used to determine an accurate estimate of relative camera motion, in some embodimeats, available GNSS measurements (e.g. carrier phase measurements) that meet quality parameters but are time-separated (e.g. by widely spaced measurement time windows ) are stitched together using relative displacement and position obtained from measurements by alternate (non-GNSS) sensors and/or techniques. GNSS signal quality parameters may include, for example, whether line Of Sight (LOS) exists to a subset of the visible GNSS satellites, the extent of GN SS signal degradation due to multipath (MP) etc.

[0022] The relative displacement and position between two time separated

GNSS positioning locations may be obtained using various sensors/techniques and may include the use of images captured by cameras/optical sensors and or measurements by Inertia! Measurement Units (JMUs). Relative displacement and position between two GNSS positioning occasions may also be determined using LIDA o Radio Detectio and Ranging (RADAR). LIDAR refers to remote sensing technology that measures distance by illuminating a target (e.g. with a laser or other light) and analyzing the reflected light. In some embodiments, VIO based techniques may be used to determine relative displacement and position between two or more locations where GNSS measurements that meet quality parameters are available. For example, in a situation where GNSS ineasureineats meeting qualit parameters are available at a time tl and then available at another later time t2, but unavailable between tl and t2, then., VIO and/or an alternate sensor based technique of similar accuracy may be used to determine relative displacement and position between times t.i and l2. The time separated GNSS rneasureraents obtained daring positioning ma include GNSS carrier phase

measurements and/or GNSS code phase measurements.

} ^' 0Q23] The term "muUipath" is used to refer to errors that occur when a UE receives a mi of direct and indirec signals or indirect-only signals (Non Line of Sight), The indirect signals may come from surrounding buildings or from atmospheric conditions affecting signals from satellites at low elevations relative to the horizon. Disclosed embodiments facili tate relative motion and position determination when the number of v isible satellites is less than the number used during traditional (e.g. 4 or more satellites for a three-dimensional (3D) mode) position calculation.

}Θ024| In some embodiments, time-separated Line Of Sight (LOS) GNSS measurements that include carrier phase measurements without roititipath may be stitched together based on VIO, for example, by dead reckoning with a camera or image sensor. In some embodiments, the GNSS measurements, when available, may also be used to correct VIO drift, offset and misalignment errors, in some embodiments, measurements can be stitched together by fusing GNSS measurements collected, for example, at a time tl, with measurements from another sensor (e.g. camera and/or ΙΜϋ and/or LIDAR and or RADAR and/or another method) or technique that determines an accurate relative motion vector between a time tl and another time t2. In some embodiments, parameters for GNSS measurements at time t2 may be determined based on the GNSS measurements at time tl and the accurate relative motion vector between times t l and i ^' 2.

|0025| Some disclosed embodiments may be viewed as facilitating the transport of discontinnous GNSS measurements collected at a first time tl. to another second time epoch 12, using relative displacement information obtained from another rion-GNSS sensor/technique (e.g. V iO IMII/LID AR/RADAR based) of similar accuracy. In ^' some embodiments, position continuity may be maintained by propagating the last fix based on the displacement measured since that last fix. Thus, a fix at time tl may be propagated to a time t2 based on displacement measured since tl . in some

embodiments, computation of a translation and/or rotation matrix to obtain

measurements in an absolute frame of reference from the local non-GNSS

displacement sensor frame of reference .may be performed in conjunction with the position fix..

(0026) In some embodiments . GNSS carrier phase measurements that meet quality parameters may be collected at both tl and t2, ViO based techniques may be used to determine displacement between times l an t2, and carrier phase integer ambiguity resolution may be performed for the GNSS measurements.

|0027| In classical Real Time Kinematic (RTK)„ GN SS measurements are simultaneously collected from two receivers: a Reference receiver and from a .Rover (moving) receiver to resolve carrier phase ambiguities, in classical RTK, the term "Relative Positioning" refers to the instantaneous baseline vector between two distinct receivers (e.g. a reference and a rover) at a point in time..

} ^{ H ⁾ 28j In some disclosed embodiments, data from the same receiver, but collected, at different times, ma be used to resolve carrier phase: ambiguities. As one example, for computations, the position p.1 of UE at time tl may be considered as the "rover receiver" position, while the position p2 of the UE at time t2 may be considered the as the "reference recei ver" position,

(0029) In some embodiments, fast resolution of integer ambiguities may be facilitated because disclosed techniques may tightly constrain VlOmeasured relative displacement to relatively high accuracy Ieveis. Accordingly, in some embodiments, the VlOmeasured relative displacement may be used, in part, to resol e ambiguities and facilitate real time position determination even when cycle slips occur, in some embodiments, carrier phase ambiguities .between two successive positions occupied by the receiver may be .resolved using the Vernier principle, in the Vernier principle, two scales {e.g. VIO-based and carrier phase based) with different periodicities or graduations may be used to increase the 'accurac of the measured displacement between the two successive receiver positions, j 01)30} Disclosed embodiments also resolve other biases relating to ^■ position determination such, as those arising from non-simultaneous GNSS measurements, the motion of satellites between times tl and tl, ionospheric delays partial spatial decorrelation, receiver clock drift, etc. In some embodiments, the techniques disclosed may also be used for and/or in conjunction with Precise Point Positioning (PPP) iechmtpies that facilitate global location determination with high accuracy using a single GNSS receiver,

(0031] The terms "User De vice" (U ) or "user equipment" (UE) are used interchangeably herein and ma refer to a device suc as a cellular or other wireless communication device, personal communication system (PCS) device, personal navigation device (PND), Personal information Manager (P1M), Personal Digital Assistant (PDA), laptop or other suitable mobile device which is capable of receiving wireless communication and/or navigation signals. The terms are also intended to include devices whic communicate with a personal navigation device (PND), such as by short-range wireless, infrared, wireline connection, or other connection - regardless ^• of whether satellite signal reception, assistance data reception, and/or position-related processing occurs at the device or at the PND. The UE may represent a mobile telephone, notepad computer, or laptop, or it may be a vehicle that collects measurement sets for the purpose providing a real time position and/or map creation,

[0032] in addition, the terms UD, UE, "mobile station" "mobile device" or

"target" are intended to include all devices, including wireless and wireline

communication devices, computers, laptops, etc, which are capable of communication with a server, such as via the Internet, Wi-Fi, cellular wireless network, DSL network, packet cable network or other network, and regardless of whether satellite signal reception, assistance data reception, and/or position-related processing occurs at the device, at a server, or at another device associated with the network. Any operable combination of the above are also considered a "u ser device."

[0033 j Fig, 1 shows a schematic block diagram illustrating certain exemplary features of UE 100 enabled to support mapping based, on a combination of GNSS signal and sensor based measurements to compute relative displacement, including camera or other image based techniques. Further, in some embodiment , _: UE 00 may also support hybrid G SS-VIO based position determination by combining image based techniques with ONSS carrier-phase signal measurements. The term "hybrid" is used to refer to the use of a combination of one or more of displacement sensor and/or V1Q based

techniques with ONSS signal based techniques to perform location detemimation in a manner consistent with embodiments disclosed herein.

| 034 UE 100 may, for example, include one or ^' more processors or

processors) 150, memory 130, a transceiver i 10 (e.g., wireless network interface), and Satellite Positioning System (SPS) receiver / GNSS receiver 140 (hereinafter 'ONSS receiver 140") and optical sensors camera(s) 180. I some embodiments, UE .100 may also optionally or additionally include one or more of; a magnetometer, an altimeter, a barometer, and sensor bank 185 (collectively referred to as sensors 185). In some embodiments, UE 100 may include Inertia! Measurement Unit (IM.U) 170.

non-transitory computer-readable medium 160, display 190, and memory 130, which ma be operatively coupled to each other with one or .more connections 120 (e.g., buses, lines, fibers, links, etc.). in certain example implementations, all or part of UE 100 may take the form of a chipset, and/or the like.

}00351 GNSS receiver 140 may be enabled to receive signals associated with one or more SPS/GNSS resources. Received SPS/GNSS signals ma be stored in memory 130 and/or used by processors) 150 to determine a position of UE 100. In some embodiments, GNSS receiver 140 may include a code phase receiver and a carrier phase receiver, winch may measure carrier wave related information. The carrier wave, which typically has a much higher frequency than the pseado random noise (PRN) (code phase) sequence that it carries, may facilitate more accurate position

determination. The term "code phase measurements" refer to measurements using a Coarse Acquisition (C/A) code receiver, which uses the information contained in the PRN sequence to calculate the position of UE 100. The term "carrier phase

measurements" -refer to measurements using a carrier phase recei ver, which uses the carrier signal io calculate positions. The carrier signal may take the form, for example for GPS, of the signal LI at 1575.42 MHz (which carries both a status message and a pseudo-random code for timing) and the 12 signal at 1227.60 MHz (which carries a more precise miliary pseudo-random code),

|0¾36 In some embodiments, carrier phase measurements ^' may be used to determine position in conjunction with, code phase .measurements and differentia! techniques, when GNSS signals that meet quality parameters are available. The use of carrier phase measurements along with differential correction can yield relative

sub-decimeter position accuracy. In some embodiments, UE may use techniques based on or variants of real-time carrier phase differential GPS (CDGPS) to determine the position of UE at various point and times, when such measurements are a vailable. The term "differential correction", as used conventionally, refers to corrections to carrier phase measurements determined by a reference station at a known location. The carrier phase measurements at the reference station may be used to estimate the residuals of (e.g.. portions not corrected by navigation messages) satellite clock biases of visible satellites. The satellite clock biases are transmitted to "roving receivers" which use the received informatio to correct their respective measurements. In some embodiments, the position pi of UE 10 at time tl may be considered as the "rover recei ver" position, while the position p2 of the UE at time t2 may be considered the as the "reference receiver" position and differential techniques may he applied to minimize or remove errors induced by satellite clock biases. Because the same receiver is used at time t l and t2„ no data needs to be actually transmitted .from the "reference" receiver (i.e. receiver at. rime tl), to the "rover" receiver, (i.e. same receiver at time t2). in some embodiments, instead of the data transmission, between rover and receiver that occurs in classical RT , a local data buffering operation may be used to hold data at times l and t2,

}0$37j The term "differential techniques" refers to techniques such as "siiigle differencing",, "double differencing" etc. where the qualifiers "single" "double" etc. refer traditionally to the number of satellites and the two receivers used in the differencing,

Ι _. Θ038) As used in relation to embodiments disclosed herein, "single

differencing" refers to error reduction techniques that subtract GNSS carrier phase measurements at a li ^' E 100 from, a single satellite S at time t2 from GNSS carrier measurements at UE 100 from: same satellite S at time tl. The term "double

differencing",, as used in relation to embodiments described herein, refers to the carrier phase double difference observable between the times tl and†2 _S which may be obtained as the difference between the above single difference carrier phase observable for a satellite SJ and the above single difference carrier phase observable for a satellite S j.

1 _. 0039] Transceiver 110 may, for example, include a transmitter 1 12 enabled to transmit one or more signals over one or more types of wireless communication networks and a receiver 1 14 to receive one or more signals transmitted over one or more types of wireless communication networks. Wireless communication networks may include, for example. Wireless Wide Area Networks (WWAN) _S ineiuding cellular networks, and/or Wireless Local Area Networks (WLANs).

J0040] In some embodiments, UE 100 may comprise optical sensors such as

CCD or CMOS sensors and or camera(s) 180. In some embodiments, optical sensors may include or be coupled to a L1.DAR unit/ lasers with associated instrumentation including scanners, photo-detectors and receiver electronics. Optical sensors / camera(s) are hereinafter referred to "cameraCs) 180", CameraCs) 180 may convert an optical image into an electronic or digital image and may send captured images to processor ^' s) 150. For example, as shown in Fig. IB, in some embodiments, eamera(s) 180 may be housed separately, and may be operationally coupled to display 1 0, processors) 150 and/or other functional units in UE i O,

{0041 I In some embodiments, UE 100 may also include Inertiai Measurement Unit (1MU 170, In some embodiments, IMU 170, winch ma comprise 3-axis aeceieromeier(s), 3-axis gyroscope(s), and/or magneiomeier(s), may provide velocity, orientation, and/or other position related information to processors) 150. In some embodiments, IMC ^" 170 may be configured to measure and output measured

information ^' synchronized to the capture of each image frame by earaera(s) 180, and/or measurements taken by sensors 185 in UE 100, In some embodiments, the output of IMU 170 may be used, in part, by processors) 150 to determine a position and orientation of UE 100.

}O042] The term "non-GNSS displacement sensor" is used herein to refer to any combination of sensors that may be used, to detemrine displacement. The term

non-GNSS displacement sensor, as used herein, ma refer to one or more of; IMUs, accelerometers, Visual Inertiai Odometry (VIO) based on captured images, ^' LJDAR etc. i i The terra "hon-GNSS rtteasurements" may refer to measurements from any of the above sensors,

|¾043J In some embodiments, the capture of GNSS measurements by UE 100 when available may be synchronized and/or correlated with the capture of images by camerais) I SO. Further, in some embodiments, the capture of non-GNSS measurements (e.g. by IMU 170) measurements may be synchronized with the capture of images by the camera(s) 180 UE 100. In some embodiments, IMU measurements, GNSS measurements, and captured images may be iimestarnped and the measurements and images may be associated with each other based on the time stamps. The association of one or more measurements with image and/or with each other may occur concurrently with measurement / image recordation, and/or at a later point in time based on the timestamps associated with the measurements.

[0644| The term "measurement set" is used to refer to signal measurement performed by a UE at a measurement location at a point in time or within some specified interval of a point in time. The signal measurements made may be related to mapping and/or position determination. The signal measurements made may also depend on UE 100, the capabilities of UE 1 0, environmental characteristics and/or signal characteristics that are available for measurement by UE 1 0 at a specific location rime. Typically, a measurement set may comprise available GNSS

ineasureinents, VIO measurements (e. g. based on captured iraage(s) or LIDAR measurements), and IMU measurements, where each element of toe measurement set may have been recorded within some specified time interval of a point in time. The measurement sets recorded by UE 100 may be stored irt memory 130 on UE 100.

[0045| Processors) 150 ma be implemented using a combination of hardware, firmware, and software, in some embodiments, processor(s) 150 may include Computer Vision Processor (CVP) 155, which may implement a variet of image processing, VIO, and Computer Vision (CV) functions.

| 6| In some embodiments, camera(s) 1 SO may include multiple cameras, front and/or rear facing cameras, wide-angle cameras, and may also incorporate CCD, CMOS, and/or other sensors. Camera(s) 180, which may be still and or video cameras, ma capture a series of 2-Dimensional (2D) still and/or video image frames of an environment and send the captured image frames to processors) 150. For example, camera I SO may capture a series of 3 -dimensional (3D) images from a Time-of-Plight camera, or associated pairs or multiple 2-dimenskmal (2D) frames captured by stereo, trifocal or multifocal cameras. In some embodiments, camera(s) 180 may b a wearabl camera, or an externa! camera, which may be operationally coupled to, bin housed separatel from, other functional units in UE 100, la one embodiment, images captured by camera(s) IS may be in a raw uncompressed format and may be compressed prior to being processed and/or stored in memory 1 0, In some embodiments, image

compression may be performed by processors) 150 (e.g. by CVP 155) using lossless or lossy compression techniques.

[0047] in some embodiments, camera 180 may be a depth sensing camera or may be coupled to depth sensors. The term "depth sensor" is used to refer to functional units- that may be used to obtain depth information for an environment independently and or in conjunction wife eamera(s) ISO. In some embodiments, may comprise RGBD cameras, which may capture per-pixel depth (D) information when the depth sensor is enabled, in addition to color (RGB) images. As another example, in some embodiments, camera(s) 180 ma take the form of a 3D Ti me Of Flight (3DTOF) camera. In embodiments with 3DTOF camera(s) 1 0, the depth sensor may take the form of a strobe light coupled to the 3DTOF camera(s) 180, which may illuminate objects in a scene and reflected light may be captured by a CCD/CMOS sensor in camera 110, Depth information may be obtained hy measuring the time that the light pulses take to travel to the objects and back to the sensor. In some embodiments, UE .100 may include or be coupled to LIDAR sensors, which may provide measurements to estimate relative displacement of UE 100 between two locations.

(004$] As a further example, the depth sensor may take the form of a light source coupled to camera(s) 180. in one embodiment, the light source may project a structured or textured light pattern, which may consist of one or more narrow bands of light, onto objects in a scene. Depth information may then be obtained by exploiting geometrical distortions of ^" the projected pattern caused by the surface shape of the object. In one embodiment, depth information may be obtained from stereo sensors such as a combination of an infra-red structured Sight projector and an infra-red camera registered to a RGB camera, in some embodiments, eaniera(s) 1 0 may be stereoscopic cameras capable of capturing 3 Dimensional (3D) mages. In another embodiment, camera's) I SO may include depth sensors that are capable of estimating depth information. For example, a depth sensor may form part of a passive stereo vision sensor, which may use two or more cameras to obtain depth information for a scene. The pixel coordinates of points common to both cameras in a captured scene may be used along with camera pose information and/or triangulaiion techniques to obtain per-pixel depth infonnatioo. In some embodiments, depth sensors may be disabled, when, not in use. For example, the depth sensor may be placed in a standby mode, or powered off when not being used. In some embodiments, processors 150 may disable (or enable) depth sensing at one or more points in time.

[0049) Processo (s) 150 may also execute software to process image frames captured by camera's) 180. For example, rocessor's) 150 and/or CVP 155 may be capable of processing one or more image frames received from camera's) 180 to determine the pose of camera's) 180 and; or UE 1.00. implementing various co mputer vision and image processing algorithms and/or performing VIO based on the images received from camera's) ISO. The pose of camera's) ISO refers to the position and orientation of the camera's) 180 relative to a frame of reference. In some embodiments, camera pose may be determined for 6-Degrees Of Freedom (6-DOF), which refers to three translation components ( which may be gi ven by Χ,Υ,Ζ coordinates of a frame of reference) and three angular components (e.g. roll, pitch .and yaw relative to the same frame of reference),

{0050) In some embodiments, the pose of camera's) 180 and/or U E 100 may be determined and/or tracked by processor's) 150 using a visual tracking solution based on image frames captured by camera's) 180. in some embodiments, processor's) 150 and/or CVP 155 may he implemented using dedicated circuitry, such as Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), and/or dedicated processor.

1 _. 0051) In some embodiments, CVP 155 may implement various computer vision and/or image processing methods such as 3D reconstruction, image compression and filtering. CVP 155 ma also implement computer vision based tracking, VIO, model-based tracking, ^' Simultaneous ^' Localization And Mapping (SLAM), etc. In some embodiments, the methods implemented by CVP 155 may be based on color or grayscale image data captured by camera(s) .1 SO, which may be used to generate estimates of 6-DOF pose measurements of the camera, SLAM refers to a class of techniques where a map of an environment, such as a map of an environment being modeled by UE 100, is created while simultaneously tracking the pose of UE 100 relative to that map, SLAM techniques include Visual SLAM (VLSAM), where images captured by a camera, such as cameras) 180 on UE 100, ma be used to create a map of an environment while simultaneously tracking the camera's pose relative to that map, VSLAM may thus i nvolve tracking the 6DOF pose of a camera while also determining the 3-D structure of the surrounding environraent i some embodiments, the techniques outlined above may identify salient feature patches or keypoints or feature descriptors in a captured image frames, which may be tracked in a subsequent image frames. Image feature descriptors may take the form of Scale Invariant Feature Transform (SIFT). Speeded-Up Robust Descriptors (SURF), etc., which are well-known in the art. The determined/stored image descriptors may be utilized at a later point by an image or object detector to determine the pose of a HE,

J0052 j Tracking the pose of UE 100 and/or camera(s) 1 SO in a spatial coordinate system can be accomplished in a variety of ways. For example, GNSS signals may be unavailable during some time periods. The term "unavailable" in relation to GNSS signals is used to refer to one or more of; a temporary loss of lock and/or discontinuities and/or interruptions of GNSS signals; various environmental (including atmospheric, geographical etc) conditions that may detrimentally affect reception and/or reliability of GNSS signals; and/or non-availability of GN SS signals. Where GNSS signals, such as carrier phase signals, are unavailable or unreliable, such as in dense outdoor environments (e.g. urban canyons), such tracking can be done using VIO based tracking, which,, in some embodiments, may use a combina tion of visual and inertial tracking systems. For example, images captured by earnera(s) 180 may be used in conjunction ith measurements by IMU 170 and/or sensors in sensor ban 85 (e.g. altimeter, barometer, magnetometer etc) to determine the pose of UE 100 and/or camera(s) 380. In another embodiment, depth data from a depth sensor, which may be captured in conjunction with the capture of a depth -image by eamera(s) 180, may be used, in part, to compute camera pose in some embodiments, ViO based techniques may be used, in part, to correct for errors (such as biases and drift) in IMU 170. When available, GNSSS coordinates may also be used to provide location information.. |Θ053| in some embodiments, the pose of the camera may be used to recalibrate sensors in IMU 170, and/or to compensate for and/or remove biases from measurements of sensors 185 aad or sensors in I U 170, For example, IMU 170 and/or sensors 185 may output measured information in synchronization with the capture of each image frame by camera(s) 180 by UE 100. When the camera pose can be estimated accurately, for example, based on the images (e.g. successful detection of one or more

corresponding feature points in images) then the VIO estimated camera pose may be used to apply corrections to measurements by IMU 1 0 and/or sensors 185 and/or to recalibrate IMU 170 / sensors 185, so that measurements by IMU 170 / sensors 185 may more closely track the VIO determined pose. jG05 J in some embodiments, a hybrid VIO Tracker may incorporate an

Extended alnian Filter (EKF), providing various inputs to the EKF to track the pose of camera(s) 180 and/or UE 100. The alman Filter (KF) is a widely used method for tracking and pose estimation. Specifically, the KF operates recursively on a sequence of noisy input measurements over time to produce a statistically optimal estimate of the underlying system state, which may include estimates of unknown variables. The EKF linearizes noa-Uaear models to facilitate application of the KF.

{ ^' 0055) Further, in some embodiments, processors) 150 may further comprise a

Positioning Engine (PE) 1.56 (hereinafter PE 156) , which may use information deri ved from images, sensor and wireless measurements by UE 100 either independently, or in conjunction with received locatio assistance data to determine a position and/or a position uncertainty estimate for UE 100. PE 156 may be implemented using software, firmware, and/or dedicated circuitry, such, as Application Specific integrated Circuits (ASICs), Digital Signal Processors (DSPs), aad/or dedicated processor (such as processors) 150).

(0056J Further, in some embodiments, processors) 150 may comprise Location

Assistance Data Processor (L AD?) 158 (hcteraafier LADP 158), which may process location assistance information comprising multipath and visibility map assistance information, updated GNSS satellite almanac and/or epheraeris information, which ma then be used by processo s) 150 to select a signal acquisition / measurement strategy and/or determine a location. In some embodiments, processors} 150 / LADP 158 may also be capable of processing various other assistance informatio such as Long Term Evolution (LTE) Positioning Protocol (LPP or LPP extensions (LPPe) messages including assistance information either directly or .in conjunction w t one or more other functional blocks shown in Fig, 1, in some embodiments, PE 156 and/or LADP 158 may be used to obtain an initial absolute location of UE 100,

} 057j In some embodiments, UE 100 may include one or mot e UE antennas

(not shown) which may be interna! or external. UE antennas may be used to transmit and/or receive signals processed by transceiver 1 10 and/or GNSS receiver 140. In some embodiments, UE antennas may be coupled to transceiver 110 and GNSS receiverMO. In some embodiments, measurements of signals received (transmitted) by UE 100 may be performed at the point of connection of the UE antennas and transceiver 1 10. For example, the measuremen t point of reference for received (transmitted) RF signal measurements ^' may be an input (output) terminal of the recei ver 1 14 (transmitter 112) and an output (input) terminal of the UE antennas. In an UE 100 with multiple UE antennas or antenna arrays, the antenna connector may be viewed as a virtual point representing the aggregate output (input) of multiple UE a tennas, in some

embodiments, UE 10 may measure received signals including signal strength and TOA measurements and the raw measurements may be processed by processor(s) 1 0. in some embodiments, transceiver 110 may include and/or be coupled to a RADAR unit, which ma be used to obtain non-GNSS displacement measurements.

|0058| The methodologies described herein may be implemented by various means depending upon die application. For example, these methodologies may be implemented using modules in hardware, firmware, software, or any combination thereof. For ^' hardware implementation, the processors) 150 may he implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (PPG As), processors, controllers, micro-controllers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or a combination thereof.

{9659} For a firmware and/or software implementation, the methodologies may be implemented using code, procedures, functions, and so on that perform the -functions described herein. Any machine-readable medium tangibl embodying instructions may ^¬ be used in implementing the methodologies described herein. For example, software codes may be storcd in hon-transitory computer-readable medium 160 or memory 130 that is connected to and. executed by proeessor(s) .150. Memory may be implemented within the processor unit or external to the processor unit As used herein the term

"memory" refers to any type of long term, short term, volatile, nonvolatile, or other memory and is not to be limited to any particular type of memory or number of memories, or type of media upon which memory is stored. In some embodiments, memory 130 ma hold program code that facilitates hybrid GNSS-VIO based location determination, image processing, and other tasks performed b CM 155, PE 156, and/or LADP 158, on processors) 150. For example, memory 160 may hold data, O SS satellite measurements, captured still images, depth information, video frames, program, results, as well as data provided by 1MU 170 and sensors 185.

(0060J if implemented in firmware and/Or software,, the functions may be stored as one or more instructions or program code on a computer-readable medium, such as medium 160 and/or memory 130. Examples include- computer-readable media encoded with computer programs and data associated with or used by the program. For example, the computer-readable medium including program code stored thereon may include program code to support hybrid GNSS-VIO based position determination

}(M½1] Computer-readable media 160 includes physical computer storage media,

A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such -non-transitory computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM, flash memory, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions and/or data and that can be accessed by a computer; disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and bin-ray disc where disks usuall reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

(0062} In addi tion to storage on com uter readable medium 160, instructions and/or data may be provided as signals on transmission media included in a

communication apparatus. For example, a communication apparatus may Include a transceiver .1 Ml, which may receive signals through receiver ! 12 indicative of instructions and data. The instructions and data may cause one or more processors to implement hybrid GNSS-VIO based position deteroiination and/or other functions outlined herein. That is, the communication apparatus includes transmission media with signals indicative of information to perform disclosed functions.

{ ^' 0063] Memory 130 may represent any data storage mechanism. Memory 130 may include, for example, a primary memory and/or a secondary memory. Primary memory may include, for example, a random access memory, read only memory, etc. While illustrated in this example as being separate from proeessorfs) 150, it should be understood that all or part of a primary memory may be provided within or otherwise eo-iocated coupied with processors) 150. Secondary memory may include, for example, the same or similar type of memory as primary memory and/or one or more data storage devices or systems, such as, for example, a disk drive, an optical disc drive, a tape drive, a solid state memory drive, etc,

}0064j In certain implementations, secondary memory may be operatively receptive of, or otherwise configurable to couple to a non-transitory computer-readable medium 160. As seek, in certain example implementations, the methods and/or apparatuses presented herein may take the form in whole or part of a computer-readable medium 1 0 that ma include computer implemcntable instructions 1108 stored thereon, which if executed by at least one proeessorfs) 150 may be ope.rative.ly enabled to perform all or portions of the example operations as described herein. Computer readable medium 160 may be a part of memory 130.

{0065] Further, tJE .100 may include a screen or display 190 capable of rendering color images, including 3D images, in some embodiments, display 1 0 may be used to. display live images captured by camerafs) 180, Graphical User Interfaces (GUIs), program output etc. In some embodiments, displa 190 may comprise and/or be housed with a touchscreen to permi t users to input data via some combination of virtual keyboards, icons, menus, or other Graphical User interfaces (GUIs), user gestures and/or input devices such as a stylus and other writing implements. In some embodiments, display 190 may be implemented using a Liquid Crystal Display (LCD) display or a Light Emitting Diode (LED) display, such as an Organic LED (OLED) display. In. other embodiments, for example as shown in Fig, IB, display 1 0 may be housed, separately and may be operationally coupled to camera 180, processors) 150, and/or other functional units in UE 100,

]0066] In some embodiments, processors) 150 may also receive input from one or more sensors in sensor bank 85 (also referred to as "sensors .185"), which may include, for example, a magnetometer, altimeter and/or barometer. The magnetometer may be capable of measuring the intensity and/or the direction of the Earth's magnetic fieid and may serve as a compass and/or provide an indication of a direction of travel of UE 100. The altimeter may be used to provide -an indication of altitude above a calibrated level, while the barometer may provide an indication of atmospheric pressure, which may also be used to obtain a determination of altitude.

|(MM>7 j In some embodiments, sensors 185 may include one or more of an ambient light sensor, acoustic transducers such as microphones/speakers, ultrasonic transducers, and/or depth sensors, which may be used to acquire depth information and/or determine distance to a target. In general, the list of sensors above in not exhaustive and sensor bank 1 5 may include various other types of sensors and transducers which are increasingly being incorporated into user devices such as vehicle mounted devices, smartphones, and other mobile devices, in some embodiments, UE 100 may not include one or more sensors in sensor bank 185. For example, one or more of an altimeter, barometer, and/or magnetometer may be omitted.

}0 68| Fig. 2 shows an architecture of a system 200 capable of providing

Location, and/or Navigation services to UEs .1 0. in some embodiments, system 200 may be used to transfer of location assistance data such as updated almanac or ephemeris data for one or more GNSS satellites to the UEs 100. la some instances, system 200 may be used for mapping or location services,, such as for use with hybrid GNSS-VK) based location/mapping, in a manner consistent with embodiments disclosed herein.

1.0069] For example, in some instances, based on the received location assistance data (e.g. by LABP 158 from, server 250) UE 100 may obtain GNSS satellite measurements, which, in some instances, may be captured in conjunction with the capture of images by camera(s) 180. The captured images and/or measurements may he used locally by UE 100 to detemiinc its location. [Θ07β| As illustrated in Fig. 2, the UE 100 may communicate with server 250 through network 230 and base station ahtennas 240-1 - 240- , _: collectively referred to as antennas 240, which may be associated with network 230, Server 250 may, in some instances, provide the functionality of one or more of a location server, location assistance server, position determination entity (PDE), or another network enti ty. The transfer of the location and other information may occur at a rate appropriate to both UE 100 and server 250.

100731 In some embodiments, system ! 00 may use messages such as LPP or

LPPe messages between UE 100 and server 250. The LPP Protocol is well-known and described in various publicly available technical specifications from an organization known as the 3rd Generation Partnership Project (3GPP). LPPe has been defined by the Open Mobile Alliance (QMA) and may be used in combination with LPP such that each combined LPP/LPPe message would be an LPP message comprising an embedded LPPe message.

|0072) In some embodiments, UE 100 may receive locatio assistance information seek as almanac / ephetneris data for one or more SVs (e.g. GNSS satellites) 280 from base station antennas 240, which may be used for position determination. Antennas 240 may form part of a wireless communication network, which may be a wireless wide area network (WWAN), wireless local, area network (WLAN), etc, A WW AN may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (F.DMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) network, Long Terra Evolution (LTE), WiMax and so on.

{Θ073 j A CDMA network may implement one or more radio access technologies (RATs) such as cdma2000, Wideband-CDMA (W-CDMA), and so on. Cdma2000 includes 1S-95, IS-2000, and 1S-856 standards. A TDMA network may implement Global System for Mobile Communications (GSM), Digital Advanced Mobile Phone System (D-AMPS), or some other RAT. GSM, W-CDMA, and LTE are described in documents from an organization kno wn as the "3rd Generation Partnership Project' ⁵ (3GPP). Cdma200 is described in documents from a consortium named "3rd Generation Partnership Project 2" (3GPP2). 3GPP and 3GPP2 documents, are publicly available. A WLAN may be an IEEE 802. i ix network. ^' The techniques may also be implemented in conjunction with any combination of W WAN, WLAN, etc. For example, antennas 240 and network 230 may form part of, e.g., an evolved UMTS Terrestrial Radio Access Network (E-UTRAN) (LTE) network, a W-CDMA UTRAN network, a GSM/EDGE Radio Access Network (GERAN), a IxRTT network, an

Evolution-Data Optimized (EvDO network, a WiMax netw rk or a WLAN.

[0074| UE 100 may also receive signals from one or more Earth orbitin Space

Vehicles (SVs) 280 such as SVs 280-1 - 280-4 collectively referred to as SVs 280, which may be part of a GNSS. SV's 280, for example, may be in a GNSS constellation such as the US Global Positioning System (GPS), the European Galileo system, the Russian Glonass system, or the Chinese Compass system. In accordance with certain aspects, the techniques presented ^' herein arc not restricted to global satellite systems. For example, the techniques- provided. erein may be applied to or otherwise enabled for use in various regional systems, such as, e.g., Quasi-Zemth Satellite System (QZSS) over Japan, Indian Regional Navigational Satellite System (IRNSS) over India, and/or various augmentation systems (e.g., an Satellite Based Augmentation System (SBAS)) that ma be associated with or otherwise enabled for use with one or more global and/or regional navigation satellite systems. By way of example but not limitation, an SBAS may include an augmentation system(s) that provides integrity information, differential corrections, ete., such as, e.g., . Wide Area Augmentation System (WA AS), European Geostationary Navigation Overlay Service (EGNOS), Mulu-i nctional Satellite

Augmentation System: {MS AS), GPS Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAM), and/or the like. Thus, as used herein an SPS/GNSS may include any combination of one or more global and or regional navigation satellite systems and/or augmentation systems, and SPS/GNSS signals may include SPS, SPS-like, and/or other signals associated with such one or more

SPS/G SS. The SPS/G SS may also include other non-navigation dedicated satellite systems such as iridium or -One Web. in some embodiments, GNSS reeeiver!40 may be configured to receive signals from one or more of the above SPS/GNSS/satellite systems.

1 _. 0075} For simplicity, only one UE 100 and server 250 are shown in Fig. 2. In general, system 100 may comprise multiple cells indicated by 245-k (0 < k < N^is, where N _ee s _h is the number of ceils) with additional networks 230, LCS clients 260, UDs KM), . servers 250, (base station) antennas 240, and Space Vehicles (SVs) 280, System 100 may further comprise a mix of ceils including microeeils and fenrtocells in a manner consistent with embodiments disclosed herein,,

| ^' 0076J UE 100 may be capable of wirelessiy communicating with server 250 through one or more networks 230 that support positioning and location services to obtain, an initial coarse location, which may be used in conjunction with

airaanae ephemeris information to determine a more precise location using hybrid GNSS-VIQ based position determination. For example, UE 100 may use a hybrid GNSS-VIO based position determination and compute its position based on measurements from one or more of: IMU 170, and/or captured images and/or, GNSS carrier phase observables (e.g. based on measurements of signals recei ved from SVs 280).

|0077| Fig, 3A shows an example skyplot 300 of eight GNSS SVs 280-1 through 280-8 at a point in time. Fig. 38 shows UE 100 in an urban environment. As shown in Fig. 3B, UE 100 is travelling along Avenue 1 along Path 310 starting at time point P0, As shown in Fig. 3B, UE 100 can receive LOS signals from GNSS SVs 280-1 and 2.80-2, However, because only 2 GNSS satellites are visible, UE UK) ma not be able to determine a full 3D location. For example, signals from GNSS S Vs 280-3, 280-4, 280-5, 280-6, 280-7, and 280-8 may be blocked or experience significant degradation due to an urban canyon environment thereby preventing MS 3D GNSS position location by UE 100.

{W78| During section 320 (which may be a 25 m section formed by the intersection of Avenues 1 and 2), after tra vel ling about .1 0 meters along pa th 310, at time t , UE 100 may receive LOS signals from GNSS SVs 280-1 , 280-2, 280-3 and 280-4, Accordingly, at point PI, UE 100 may be able to calculate full accurate 3D location based on carrier phase measurements from LOS signals received from GNSS SVs 280-1, 280-2, 280-3 and 280-4.

[0079J However, when UE travels along section 330 of path 310, UE 100 may lose signals from GNSS SVs 280-3 and 280-4, which may be blocked or experience significant degradation including multtpath due to the urba canyo environment. {0080] UE 100 may obtain / re-acquire a lock on GNSS SVs 280-3 and ^' 280-4 In

25 m section 34 (which may be formed by the intersection of Avenues i and 3) of path 310, For conventional GNSS location determination schemes using carrier phase observable*, a constant lock with GNSS SVs 280-1, 280-2, 280-3, and 280-4 is needed to calculate UE position. Cycle slips, such as may occur in section 330, may prevent die use of traditional carrier phase based accurate GNSS position location.

[00811 In some embodiments, during movement in section 330, one or more non-GNSS based positioning techniques may be used to determine the location of UE 100 by measuring displacement relative to the last GNSS carrier phase determined position. The terms "non-GNSS positioning sensor ⁵ "non-GNSS positioning techniques", "non-GNSS position determination sensor" are used synonymously herein and refer to measurements by sensors and/of by techniques that do not depend on GNSS and may be used to determine the position of UE 100, For example, measurements provided by VIO and/or 1MU 170 and/or a LIDA ^' senso may be used to determine relative displacement. During travel in section 340, when UE 100 may re-acquire a lock on GNSS SVs 280-1, 280-2, 280-3 and 280-4, the known VIO determined location of UE 100 may be used to resolve carrier phase ambiguities as described further ^' below.

{ ^' 0082] Fig, 4 shows traditional carrier phase measurements 410 and exemplary

Hybrid G ^' NSS-VJO carrier phase measurement 450 in accordance with some disclosed embodiments. Traditional carrier phase measurement compares the continuous satellite carrier signal 420 with the receiver reference clock 430 to determine total phase φΐ 422, which may then be used to determine position PI 470 of a UE at a given time. In conventional techniques, continuous -carrier phase measurements are used to determined position s at subsequent times. For example, if (he phase at position P2 480 is φ2 428, then the phase difference 425 of the total phase given by Αφ - φ2 ~φ\ of carrier signal 420 ma be used to determine and track the positio of a UE,

|0083| Carrier phase measurements include an integer cycle ambiguity or carrier phase ambiguity" N'\ The integer cycle ambiguity represents the number of ^' Ml phase cy cles between the satellite and the receiver at the time the recei ver first locks on to a GNSS satellite signal. The integer cycle ambiguity does not change from the ^' time the receiver locks on until the end of the observation period, unless the signal is interrupted and/or lock is lost. When the receiver reacquires the signal, the integer ambiguity has changed and the receiver count of the number of integer cycles from die time of initial lock is lost. Therefore, in conventional techniques loss of lock involves re-determining the integer ambiguity to when the carrier phase signal is reacquired. Further, the loss of lock also incurs a loss of accurate relative positioning until earner phase signal reacquisition is achieved.

[0084] In conventional positioning, cycle slips, which may occur because of environmental reasons, may degrade positioning accuracy. Cycle slips refer to discontinuities or interruptions in the series of carrier-phase measurements due to a receiver temporarily losing its lock on the carrier of a GNSS signal. For example, as shown in Fig. 4, interrupted carrier signal 460 is lost between good measurement window 1 462 and good measurement window 2 468. During the time that GNSS signal is interrupted, in con ventional carrier phase positioning, the receiver loses count of the number of consecutive changes in full phase cycles, which introduces errors and affects the accuracy and reliability of positioning. Thus, to maintain accuracy the process of resolving integer ambiguity is restarted. Moreover, because a loss of lock is not uncommon when odoraetry is performed in urban canyons, the use of carrier phase based techniques in conventional odoraetry has been constrained.

{ ^' 0485] In some embodiments, using hybrid G SS-VIO carrier phase measurements 450, the relative displacement in the satellite direction may be determined to be M) _m 465 between good measurement window 1 462 at posi tion PI

470 and good measuremen window 2 468 at position P2 480. in general, any nonTi SS positioning technique of similar accuracy may he used to determine the relative displacement in the satellite direction. In some embodiments, when GNSS carrier phase measurements are not available to UE 100 (e.g. after good measurement window i 462), then VIO measurements may be taken until the GNSS carrier phase measurement is once again available at measurement good measurement window 2 468. Accordingly, the phase difference Αφ 455 between good measurement window 1 462 and good measurement window 2 468 may be given by in some embodiments, Equation (I) may be used in a hybrid GNSS-VIO position determination system, to calculate phase difference between two instants t ^' l and t2 in time w en GNSS measurements are available, even if carrier phase GNSS signals are unavailable between times tl and t2. When UE 1 0 first acquires GNSS signal from an SV at good measurement window i , the acquisition may begin initially at some fractional phase \ 452. Similarly, when the hybrid GNSS-VIO system on UE 100 reacquires the GNSS signal from the same SV at good measurement window 2, the acquisition may .restart at some fractional phase ^' 2 458. In some embodiments, the relative displacement &D _m , 465 in. the satellite direction between points PI 470 and P2 480 may be measured using VIO or another non-GNSS method of sirailar accuracy. The relative displacement Δ£) _;¾> 465 may be used to calculate the phase difference A<p 455 using equation (1) above.

JiMi J Fig, 5 shows a UE 1 0 which may be in a vehicle at location PI 520 at time ti and travel to location P2 53 at time t2 along path 510 (shown, by the dashed line). At time tl , SV 280-1 is at position SI 1 540, while at time 2, SV 280-1 is at position -SI 2 550. Furthers at time tl, SV 280-2 is at position S21 560, while at time t2, SV 280-2 is at position S22 570. In some embodiments, ephemeris data may be used to determine locations SI.1 540 and S21 560 at time tl . if the lock to one or more satellites is lost during travel on path 51 , then, in some embodiments, non-GNSS positioning techniques (e.g. VIO) may be used to determine the position of UE 100 at time t2. Accordingly, in some embodiments, when carrier phase ambiguities are resoived at time t2, the movement of satellites: between times tl and t2 may be taken in to account. For example, the displacement of UE 100 relative to SV 280-1 at satellite position S12 550 and SV 280-2 at position S22 570 may be determined and used to resolve carrier phase ambiguities. In some embodiments, ephemeris data may be used to determine locations S.12 550 and S22 570 at time t2. In some embodiments, ephemeris data may be stored in memory 130 of U E 100 and/or an updated ephemeris may be obtained from wireless communication network 230 (Fig. 2).

|0687J In some embodiments _* accuracy of a hy brid GNSS- IO (or a hybrid system using GNSS with another non-GNSS positioning technique of similar accuracy) may be maintained by leveragi n the integer nature of the ambiguities similar to when using Real Time Kinematics (RT .) or Carrier Phase relative positioning, or recent Precise Point Positioning/Real Time Kinematics (PPP/RTK) methods. Double differencing between a pair of saieilites cancels out iiactiosial part of the ambiguities; the remaining ambiguities are an integral number of wavelengths.

1.0088] in some embodiments, the integer nature of the ambigui ies may be exploited to: (i) increase the accuracy of VIO displacement measurement (eg, to the order of a decimeter or less) thus compensating for VIO drift when aligning the local VIO spatial reference frame within a global reference frame; and (ii) to solve for all double difference ambiguities between two points successively occupied by the .same GPS/GNSS receiver,

(0089] In some embodiments, UE 100, (which ma be in a vehicle, including an aerial vehicle) may collect fractional carrier phase measurements for all: visible satellites at a time tl (which may correspond, for example, to good measurement window 1 462 in Fig. 4). In some embodiments, measurements may be collected for signals meeting preset quality parameters. For example, outliers may be detected and eliminated. As another example, signals with large muitipath distortions may be detected and eliminated.

10090] At time t2 (which may correspond, for example, to good measurement window 2 468 in Fig. 4), the same UE 300 collects another set of fractional carrier phase data, when good quality signals are available.

[0091] In some embodiments, VIO may be used to obtain an estimate of the relative displacement of UE 100 shown by length of 012 baseline 580 (or the distance) between position PI 520 at time tland position P2 530 at time f2. In some

embodiments, the accuracy of the estimate ma depend on the baseline distance between two locations.

[0092] Fig. 6 illustrates an example of single difference earner phase integer reconstruction / back projection according to some disclosed embodiments. Fig 6 shows a simplified illustration of single difference case for a relative angle ΰ, between the

LOS of satellite 28iW and UE displacement represented by D12 baseline 580. In some embodiments, when the elapsed time period between positions Pi and P2. is short, the angle of SVs 280 (e.g. SV 280-1) relative to positions Pi and P2 may be may be viewed as relatively constant over the time period. [Θ0 3| The carrier phase difference measured for the satellite 280-1 at two positions Pi 510 and P2 520 by the same receiver is projected onto the baseline between positions PI 510 mid P2 520. la the single difference example of Fig. 6, for each sateiiite, the distanc difference in the LOS direction of the sateiiite generates a periodic likelihood function due to the integer nature of the lambda carrier phase ambiguity. The periodic likelihood function can be thought as a series of narrow Gaussian curves, exhibiting a periodicity X in the direction of the satellite,

| 094 The projected phase difference has periodicity different from .lambda

(λ) 650 .The periodicity of the projected phase difference may he obtained as

(λ / cos{ 0 _t )), where 0 _t is the angle between LOS direction of satellite 280- and D12 baseline 580, Fig 6 shows angle θ _} between LOS Ϊ 61 of sateiiite 2.80-1 relative to

D12 baseline 5S0 with full integral phase X 650 periodicity given by (λ c s(^ }} 660-1, and angle i¾ between LOS 2 62,20 of satellite 280-2 relative to baseline 580 but wit different periodicity (X /cas(#, )) 660-2, due to different satellite to baseline angle.

|0O95f As shown. in fig, 6, the likelihood, function when re-projeeted onto the

D !.2 baseline 580 exhibits a different periodicity given by, λ / cos( f¾ ) which depends on. the relative angle & _i between, the LOS of satellite 280- and the displacement (e.g. D.12 baseline 580) baseline of UE 100. The likelihood of the difference of two projected single differences for SVs 280-1 and 280-2 provides another compound likelihood function of similar periodic behavior, but with a different periodicity given by

A \ I A \

COS(#( ) } { COS(# ₂ ) }

}00 6| When the angles # _s and <¾ are close, the periodicity becomes arbi trarily large, and the number of possible solutions (i.e. for a non zero likelihood function) for the baseline becomes very small. The increase in periodicity interval may be accompanied by an increase in width of the non zero domains (uncertainty). In some embodiments, by multiplying all the projected double difference likelihood functions, along with the VIO likelihood function (e.g. a single Gaussian with standard deviation equal to the VIO displacement uncertainty ), the number of non zero domains may be reduced and a unique VIO displacement solution may be obtained. [0 9?| The combined likelihood function will have a vary limited num er of peaks. The correct length of D12 baseline 580 corresponds to one of the peaks, A first estimate of the length of D12 baseline 580 may be obtained based on die peak location. The first double difference solution is termed the "float ambiguity solution" or "float solution" because the ambiguities are estimated as real or floating point numbers. When the float solution is re-projected onto each satellite LOS, the float ambiguities are fixed and double difference integers may be solved and a single integer solution may be determined.

}Θ0 8| In some embodiments, the VIO displacement estimate may be obtained as a maximum of the combined likelihood function. The maximum of the combined likelihood functio may exhibit a peak ^' much narrower than the initial VIO uncertainty, thereby impro ving die VIO displacement solution beyond the VIO uncertainty. In some embodiments, each integer double difference ambiguity may then be extracted by subtracting the projected double difference fractional carrier phase from the computed VIO displacement: estimate, and then dividing by the apparent periodicity along the baseline.

{ ^' Q099J The above description is merely exemplary and for illustrative purposes only . Other integer ambiguity resolution approaches such, as varying the displacement distance, and finding the maximum likelihood over the explored distance domain may also be used, in some embodiments, mixed float and integer variable maximum likelihood estimation techniques such as LAMBDA or Mixed Integers Least Squares (MILES) may be used. In some embodiments, the likelihood function re-projections are parameterized with the orientation and translation errors around initial rotation and translation matrices, and orientation and translation errors may be determined in conjunction with the VIO displacement

{OdlOO ^' j In some embodiments, the accuracy of the DI2 baseline 580 length estimate may be further improved by re-projecting the integer distance onto the D12 baseline 580, then averaging all estimates by a variance weight. For example, each double difference-based estimate of the baseline will have a different associated uncertainty, thai is twice the carrier phase one-sigma noise (assuming that all 4 carrier phases have the same noise standard deviation), multiplied by the .re-projection factor onto the baseline. The re-projection factor may be determined as As the re-projection factor is different for each double

difference, the accuracy for the baseline can be improved by computing a weighted sum of all. double difference contributions, roe weight being inversely proportional to the re- projection factor.

[00101] A simple form of the earner phase observahies may be written as: λ φ*¾) - \\(P ^l - P,)jj - c. (τ _χ ( - τ^)) - N - λ. ψ ίί,) - |(Ρ' ^· - P,¾)}| - c. (T ₂ (t _f ) - r ^l (t _f » - ^ Atf = ||(ρ' - P,)|j - c. (tiit;) - xHtd) - A. JV/

where,

A is GPS LI wavelength

is the fractional LI carrier phase measured at receiver r (^=(1,21) from sat s (in fraction of cycles)

P* ^" is the position of satellite s

P ₃ is the first (fixed) position

P ₂ (¾) is the secon position of the receiver at. time ¾

T ^4' <¾) is die clock offset at satellite s at time t ₍ ;(in seconds)

T,. (i j) is the clock offset at receiver r at time ¾ (in seconds)

/V,? is the integer number of wavelength ambiguities from satellite s to receiver r, on the total distance from satellite to receiver.

[00162] The Single difference equations may be writte as:

i- ( ύ ~ (¾(**) ~ P o$& ~ c. (¾(*,) ~ it,)) ~ L (Ni ~ Ni) . (φ' (£ _£ ) ~ [¾}) - (P,(t _f ) ^» P, _. ). cos ® ^s ~ c. (τ ₂ (¾) ~ ~ λ. (Νΐ ~ N.j)

0 ^s is the angle between the baseline from position I to position 2, and the direction of satellite s.

100103] The double difference equations may be written as:

- - ^{cos© ¹ - cose - A. [ ^' ( 2 - Ni ^! ) ~~ (Νξ ~ Ν()

(cos β'— cos θ-*)

+

(cos © - cos @ ) ^ι · ^; '

|Θ01.84] The minimum step size for the double difference ambiguity increase (or decrease) is ±1 . The associated (discrete) step size for PI to P2 distance is

- - jr nd can be larger than A .

(cos€> -cose- J

{00185] When the likelihood function of (¾¾)— P _s ) is plotted against the integer double difference a set of periodic Gaussian functions is obtained, with a period mean value of 7 ~~ κ and a standard deviation of 2 *

{ cos & -co$®> } cose™ - os 8 « j· std(<p).

{00106 Each distinct pair of satellites provides one corresponding likelihood function, with a corresponding periodicity and the fractional phase or offset.

100187] The overall likelihood function may be determined as the product of all likelihood functions by pairs of satellite, multiplied by the likelihood VIO function (centered around vector combination of VIO), with a standard deviation combination of the VIO displacement estimate error.

[00108] In some embodiments, for an "integer solution" each "float" value of the double difference ambiguit is replaced by its closest integer. Each double difference provides a ne integer estimate of VIO, weighted with the back-projected standard deviation. T he fi nal VIO displacement estimate is the weighted average of all the individual estimates. fO0109] As outlined above, disclosed hybrid GNSS-VIO position determination methods permit: position determination even when there are discontinuities in phase

3 i tracking. Disclosed, embodiments facilitate carrier phase integer reconstruction even when tracking is lost, between two times ί 1 and t2.

[OOllGj Fig. 7 illustrates back projection using VIO or another noii-GNSS positioning estimate of relative displacement between points Pi 510 and P2 520 to resolve integer ambiguities for SVs 280- 1 and 280-2,

(001 J J J Fig 7 shows the same baseline distance D12 680, with di fferent back projected single difference measurements. The first VIO distance estimate is the direct VIO distance estimaie 705, the second ViO distance estimate 715 is the back projected single difference of the satellite 280-1 with periodicity 710, the third VIO .distance estimate 725 is the back projected single difference of the satellite 280-2 with

periodicity 720, and so on. All these Hseasureraents pertain to the same baseline distance, but with periodic structures of different periodicities. Gi ven the known accuracy of the direct VIO distance estimate 705, a set comprising the number of periodicities associated with each VIO distance estimate (e.g. 715, 725 , , .) may be determined, A relative displacement between points PI 510 and P2 520 may thus be determined where the non zero domains of the likelihood functions are aligned with each other. n some embodiments, die VIO displacement estimate may be obtained as a maximum, of the combined likelihood function,

| _. 0O112J Fig, 8 shows an exemplary method 800 for .hybrid G SS-VIO or hybrid GNSS - noB-GNSS position determination in accordance with some disclosed

embodiments. In some embodiments, method 800 may be performed by a single UE 100. In some embodiments, method 800 may be performed by processors ) 150 and one or more of FE 156 or CVF 155 on UE 100.

(00113] In the method below GNSS carrier phase measurements aad othet VIO /sensor measurements may be taken and recorded by UE periodically at some specified time intervai ¾. For example, every t, time units starting at a time ¾. Corresponding timestamped VIO and GNSS CP measurements ma also be recorded and stored in memory. Further, the measurements may be stored in a FIFO, ^' The FIFO may be indexed, by satellite pairs and/or a separate FIFO may be maintained for each satelli te pair for which measurements have been obtained within some specified time interval of the current time. [00114] Jn some embodiments, in block 805. as iniiial posi ion estimate and velocity estimate for tJE 1 0 may be determined, for example, in absolute co-ordinates from GNSS measurements, or by any other suitable approach. For example, the position may be determined in Earth Centric Earth Fixed (ECEF) coordinate frame. In some embodiments, for example, when using GNSS, the initial position estimate and velocity estimate of UE 100 may be determined from pseudorangc and Dopplcr .measurement. In some embedments, the initial position estimate may be an approximate location. For example, the inaccuracy associated with the initial position estimate may be of the order of 100m or more.

|G01 IS) Further, in some embodiments, in block 805, a counter "k" winch maintains a count of the number of elapsed time intervals fy. ~ k since the initial .position, estimate at time to is initialized and set to 0, In some embodiments, in block 805, a VIO process may be started. Is some embodiments, the VIO process may nm continuously to independently determine the relative position and displacement of UE 100.

}00116j In some embodiments, in block 810, VIO-ECEF Rotation and

Translation Matrices, which may include parameters to convert relative VIO

measurements in the local VIO coordinate system to an absolute coordinate system, (eg, ECEF), may be initialized. In sortie embodiments, the initial position estimate of UE 100 at time to may he selected as the origin of a local VIO coordinate system. For example, the VIO frame of reference may be initialized with one axis in the vertical direction and with the initial orientation set at 0. VIO based displacement and camera pose (or UE pose) may be obtained in 6 Degrees of Freedom (6DOF) in the VIO local frame of reference. All the subsequent VIO positions and orientations will be cumulated translations and rotations from this initial position. In some embodiments, VIO-ECEF rotation and translation matrices may be determined based on the initial position of UE 100 in the absolute reference frame and the ini tial position of U E 1 0 in the local VIO reference frame, fCM!l 17) In block 813, the counter k may be incremented and UE may attempt t obtai the first/next available GNSS carrier phase measurements. [00118] Jn block. 815, at a first or .next time t , if a sufficient slumber of GNSS carrier phase measurements: a available (Ύ' in block 8.15),. then, in block 817, the position of UE 100 may be obtained based on die available GNSS carrier phase measurements. Further, the determined position of U E 100 may be used to refine the VIO-ECEF translation and rotation matrices. In some embodiments, the VI ) determined position may be corrected based on the refined VIO-ECEF translation and rotation, -matrices. Hie process ma then return to block 813. O01 % 9] In some embodiments, if the number of satellites fo which GN SS earlier phase measurements are available is insufficient to determine the position of UE 100 ("N" in block 15). then, in block 820, the availability of corresponding GNSS earner phase measuremen ts for at least one pair of corresponding satellites is determined.

{00120] In some embodimen ts, in block 820, if corresponding GNSS

measurements for at least one pair of corresponding satellites are not available fN" in block 820), then, another iteration is begun at biock 813. Further, in some embodiments, the VIO determined position and displacement at time t¾ ^~ *t _s may be stored i memory 130.

{00121] If corresponding GNSS measurements for at least one pair of corresponding satellites are available ("Y" in block 820), then, in. block 825, at time ¾ _» , the av ailable GNS S measurements may be recorded. In general , if GNSS carrier phase measurements for "if satellites are available, then, the measurements may be grouped by satellite pairs so that a total of -— ~— -measurements corresponding to distinct pairs of satellites may be obtained from the -measurements of the n satellites, in some embodiments, satellites for which GNSS carrier phase measurements arc available may be grouped in pairs and the measurements associated with one or more satellite pairs may be stored in a FIFO in memory 130 of UE 100.

(00122] in some embodiments, in block 835, the FIFO (in memory 130 of U E 100) may be cheeked to determine if the CP measurements in the FIFO include prior CP measurements for at least one pair of currently (at time fc) measured satellites that were previously measured together within some time window of the current time. [00123] if the FIFO does not include prior measurements for at least one pair of currentl measured satellites within the time window ("N" in step 835), men, in block 840, the GNSS carrier phase measuremen s for time ¾ may be stored and counter k is incremented prior to beginning another iteration in block 813.

[001 4] If the FIFO includes prior measurements within some time window for some number q (q >. i) pairs of currently measured satellites ("N" in ste 835), then, in block 845, the most recent of prior earner phase measurements for the q curre tly measured satellite pairs may be validated.

[00125) If the most-recent of prior measurements for die q currently ea ured satellite pairs occurred at time ^::: (k ~p}% , then, the validation may be determined from the double difference of the snapshots of the carrier phase observabi.es for the r (r < q) satellite pairs (feat were measured both at time hi nd time t _{ ¾. _p) s;. in some embodiments, the double difference of the snapshots of the earner phase observabies for the r satellite pairs measured at times and time %. _p( *i may be projected onto the baseline and validated against VIO displacement that occurred during the time interval p*t, between k*t, and (k -/>)*¾.

[00126] In some embodiments, the VIO displacement in between times ¾ and t¾-p> _* i may he determined based on the difference between the VIO determined. UE pose at time k*tj and the VIO determined UE pose at time (fc-p)*¼. The VIO pose of the UE at given tim may be determined by tracking features in images captured by a camera coupled to the UE and/or IMU measurements. For each of the r satellite pairs, corresponding measurements that are validated may be tagged as validated and a corresponding count of validated measurements for the satellite pair may be incremented. For example, a subset $ {a < r) of the r satellite pairs may be tagged as validated and, for each of the satellite pairs, the corresponding count of validated measurements may he increased,

[60127) In some embodiments, in block 850, the number of validated

measurements for each of the s; satellite pairs is compared to a threshold.

(00128| I f, for each of the 5' validated measurements, die corresponding number of validated measurements is less than the threshold f'hT step 850), t en, in block 840. the G SS carrier phase measurements for time ty may be stored, and counter k is incremented prior to beginning another iteration in block 813,

}00129j If, for at least one of the * validated .measurements, the corresponding number of validated measurements is not less than the threshold ("Y" la step 850), then, in block 855, the translation and rotation matrices at time k*¾ may be determined based on the at least one validated double difference measurement in ,s.

|0O130| Further, in block 855, a corrected VIO displacement, which compensates for the VIO drift, may then be determined using Vernier's principle (e.g. a described abo ve in relation t Figs, 6 and 7). In some em odiments, based on the corrected accurate VIO determined displacement, _, the double difference traditional observab.es may be reconipui ed, and integer ambiguities may be solved. For example, several likelihood functions with different respective periodicities may be used along with {he estimated ViO/non-GNSS measurement to determine a maximum of all the likelihood functions, In some embodiments, the maximum of ail the likelihood functions may be determined as that displacement where all the non zero domains of each likelihood function are aligned wi th each other within the known accuracy of the VIO

measurement.

{00131! In. some embodiments, based on the at least one validated double difierence measurement in * traditional double difference equations may be formed and the known double difierence integer ambiguities may be injected into the equations,

(00132] In some embodiments, corrections to ail Independent parameters of translation and rotation matrices may be determined using global bundle adjustment. In global bundle adjustment, multiple double differences (for the same satellite pairs) measured at multiple time instants are used for matrix corrections at multiple instants. The depth of the bundle estimation may be adjusted depending on the severity of the VIO drift. The depth of the FIFO may also be adjusted accordingly. In some

embodiments, the corrections, which compensate for iranslational and rotational VIO drift, may yield accurate translation and rotation matrices, which may permit

determination of the VIO determined pose in absolute coordinates. [00133] In block 860, the position of UE .100 may be computed in absolute coordinates (e.g. ECEF coordinates). The rotation and translation matrices solved for in step 855 are directly used for absolute position computation.

1.00134] Fig. 9 shows an exemplary method 900 for hybrid GNSS-VIO or hybrid GNSS - non-G SS position determination in accordance with some disclosed embodiments, In some embodiments, method 900 may be performed by a single UE 100. In some embodiments, method 900 may be performed by proeessorfs) 150 nd one or more of PE J S6 or€VP 155 on lJE 100.

[00135] In some embodiments, in block 910, a first absolute position of the UE at a first lime (tl) may be determined (e.g. by UE 100) based on GNSS measurements from a set of satellites at the first time (tl). In some embodiments, the first absolute position of the UE at a first time (tl ) ma be determined and/or obtained using any appropriate method.

[00136] In some embodiments, in block 920, at a second time (i2), a first displacement of the UE relative to the first absolute position may be determined, wherein the second time (t2) is subsequent to the first time (tl), wherein the

displacement is determined using non-GNSS measurements.

|00137{ The non-GNSS measurements may include one or more of: Visual Inertia! Odometry (VIO) measurements, and/or measurements provided by an IMU, and/or Light Detection and Ranging (LiDA ) measurements, and/or Radio Detection And Ranging (RADAR) measurements, in some embodiments, the VIO measurements used to ^' determine displacement may ^" be based, at least in part, on: tracking a plurality of features across a plurality of images captured by a camera coupled to the UE to obtain a 6 Degrees of Freedom (6DOF) pose of the UE relative to the first absolute position, wherein the plurality of images are captured in a time interval between the first time (tl ) and the second time (t2), or tracking optical flow from the plurality of images,

[00138] In some embodiments, i block 930 , a second estimate of the

displacement of the UE relati ve to the first absolute position may he determined at the second time (t2) based, in part, on: (a) GNSS carrier phase measurements at the secood time (t ^' 2 from a subset comprising two or more satellites of the set of satellites, and (b) the first estimate of the displacement of the UE. |0013 ] in some embodiments, the GNSS carrier phase measurements for satellites in the set may be unavailable between the first time (tl) and the second time itl); or intermittently available between the first time (tl) and the second time (i2), or continuously available between the first rime (tl) and the second time (t2). As one example, all or part of GNSS measurements may be unavailable between times tl and t2 because of; a temporary loss of lock and/or discontinuities and/or interruptions of GNSS signals; various environmental (including atmospheric, geographical, etc) conditions that may detrimentally affect reception and/or reliability of GNSS signals: and/or non-availability of GNSS signals. In embodiments such as ADAS, the second estimate of the displacement of the UE may be used, for example, to correct drift, biases, or other errors .of the eon GNSS sensor, j<HH40) In ^' some ^' embodiment, the ^' second estimate of the displacement of the UE may be determined by resolving a corresponding carrier phase ambiguity for each satellite in the subset based, in part, on: (a) GNSS carrier phase measurements for satellites in the subset at the first lime (tl), and (b) the fust estimate of displacement of the UE, in some embodiments, the corresponding carrier phase ambiguity tor eac satellite in the subset of two or more satellites may be resolved by; determining one or more satellite pairs in me subset of two or more satellites, and projecting, for eac h satellite pair of the one or more satellite pairs in the subset, a corresponding periodic likelihood function on to a baseline represented by the first estimate of the displacement of the UE. Each periodic likelihood function may be based on the corresponding doable differenced GNSS carrier phase measurement tor the satellite pair. Further, a combined likelihood function may be determined as a function of the corresponding periodic likelihood functions for the one or more satellite pairs and a non-periodic likelihood function corresponding to the baseline. Integral carrier phase ambiguities for each satellite may then be determined based, in part, on the combined likelihood function. In some embodiments, a second estimate of displacement of the UE may be determined based,, in part, on a maximum of the combined likelihood function and the first absolute position.

(001411 In some embodiments, a second absolute position of the UE may be determined based on the second estimate of displacement of the UE. In some embodiments, the method may further include correcting one or more of; a plurality rotational rameter, or a plurality- of ranslational parameters, wherein the rotational parameters and the translatidnal parameters -are- used to transform, the nou-GNSS measurements from a local coordinate system to an absolute coordinate system used to represent the first absolute position and the second absolute position.

{ ^' 00142J The methodologies described herein in How charts and message flows may be implemented by various means depending upon the application. For example, these methodologies may be implemented in hardware, firmware, software, or any combination ihereef For a hardware implementation, the processor 1 152 may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or a combination thereof.

|Θ0143{ Although die disclosure is illustrated in connection with specific embodiments for instructional purposes, the disclosure is not limited thereto. Various adaptations and modifications may be made without departing from the scope

Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description.