BACKGROUND

1. Field of the Invention

The present invention relates to utility location service methods and equipment, and more particularly to those that merge photographic, ground penetrating radar tomographic, and electromagnetic gradiometer tomographic images each registered to land survey monuments and GPS navigation data for a composite view to guide digging.

2. Description of the Problems to be Solved

Local utility construction and infrastructure plans and documents typically reference local land survey monuments to define precisely where each underground element should be placed. Such infrastructures include underground utilities, wires, cables, and pipes.

Finding existing, stray, broken, lost, forgotten, misplaced, prohibited, or unlawful segments of pipes,

utilities, and wires buried in the soil can be important for any number of construction, maintenance, security, defensive, economic, and operational reasons. Old maps, diagrams, notes, memories, and visual spotting are unreliable, unavailable, and can contradict one another. Conventional electronic methods of utility location service have not been performing as well as needed . SUMMARY OF THE INVENTION

Briefly, a method of land surveying electronically registers together multi-layer underground and surface images of a surface volume with buried utilities and other

infrastructures. Such method further comprises assembling and presenting the combination to a device in the field that visually guides crews in their safe digging of the ground nearby. The orienting, scaling, and registering of a first image layer is to a standardized orientation and scaling on a map of a photograph of a land surface from a zenith point in space above. Then the orienting, scaling, and registering of a second image layer is made to the standardized orientation and scaling on the map. This layer is a result of an ground penetrating radar investigation of buried objects point-by- point in an immediate search area of a corresponding ground surface. Underground buried objects and utilities are thereby located to make safe digging nearby.

These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.

IN THE DRAWINGS

Fig. 1 is a perspective view diagram representing how each vertical column of earth is scanned with various GPS, camera, GPR, and EMG sensors to each produce a "tile" in a stack, and how many such stacks are assembled to

electronically visually represent the buried infrastructure in a search area on a mobile device;

Fig. 2 is a schematic diagram of a multi-sensor data collection vehicle that is moved over the surface of a search area shown here in cross-section, multispectral sensors and tomography produce the tile scans of Fig. 1 that collectively represent the buried infrastructure in a search area;

Fig. 3 is a perspective diagram of how a whole search area of multi-sensor data collection is collected point-by- point into a database. Image processing is used to update and refresh a user display screen of maps with overlays of the buried infrastructure in the search area;

Fig. 4A is a schematic diagram of a horizontal magnetic dipole antenna, and a graph of its gradiometer response to a buried object scattering an electromagnetic radio signal;

Fig. 4B is a schematic diagram of a vertical magnetic dipole antenna, and a graph of its gradiometer response to a buried object scattering an electromagnetic radio signal;

Fig. 5 is a perspective view diagram of how six VMG antennas can be flown in two arrays on vehicle outriggers over both shoulders of a road to collect multispectral radio images of buried pipes, wires, and other infrastructure directly below;

Fig. 6 is a perspective view diagram of the constituent image layers from a variety of sensors and time frames that combine into a meaningful composite display on a mobile device for guiding a user in local digging; Fig. 7 is a cross sectional diagram of soils m which a tunnel and a PVC pipe are disposed, and that highlights the formation of conductive deposits from the bio-activity of anaerobic bacteria that coat these structures and render them visible during radio electromagnetic imaging even though they themselves are not radio reflective; and

Fig. 8 is a flowchart diagram of a method embodiment of the present invention for collecting and assembling drawings and images into a composite display to guide digging.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A method of mapping underground utility infrastructures and other buried objects includes investigating buried objects point-by-point in an immediate search area of a ground surface radio illuminated by a radio broadcast transmitter in the 500- kHz to 1, 000-kHz band transmitting from a location outside the immediate search area. Then, sensing together short-wavelength reflections of 100-MHz to 2,000-MHz and long-wavelength scattering of the electro-magnetic radio energy of the radio broadcast transmitter from buried objects underneath in layered soils with a surface-based measurement of buried- object signals using at least a phase-coherent elimination of ground surface reflection noise of at least sixty decibels in digital signal processing with a field programmable gate array (FPGA) . Then interpreting signals and displaying visual representations and characteristic descriptions of underground utility infrastructures and the buried objects sensed

together, located, and clarified, with a mapping apparatus capable of displaying aeronautical charts, satellite images, elevation maps, and geographically referenced overlays that can be displayed and printed over any map background.

Buried-utility-detection embodiments of the present invention leverage the electromagnetic (EM) radiation from conductive objects in the soils that results from the radio energy they absorb from local long wavelength AM-radio broadcasts in the 500-kHz to 1-MHz radio spectrum. The horizontal electric fields from such broadcasts will induce secondary current flow in conductive soil anomalies that forming current concentrators such as pipelines, utilities and anaerobic bacteria dominated plumes . Any underground

conductors if energized by electric fields lines of force accelerate mobile charge that re-radiate ( scatter ) long- wavelength AM Broadcast radio signals . Long-wavelength

electro-magnetic field are scattered ( instead of reflected) in the form of spherically and/or cylindrically spreading

wavefronts surrounding current concentrators with part of the radio energy traveling up ward to the surface where their gradients over short distances (spatial gradients ) are

detectable by a gradiometer. When the electrostatic shielded vertical magnetic dipole (VMD) gradiometer antennas are separated by a fixed separation distance ( δ), the utility burial depth (h) is given by (G _nu ii ^{2 _} δ ² ) ^½ where G is the surface distance between the gradiometer response nulls. Without loss of generality, differential VMD measurements made at

separation distance ( δ) determines the gradiometer response. Our United States Patent US 7,675,289, issued March 9, 2010, provides important details of construction, operation, and use of electromagnetic gradiometers (EMG's), but the EMG ' s we now use in embodiments of the present invention are improvements over our 2010 state-of-the-art where opportunistic high power AM Broadcast Band towers are widely available on the arable land surface of the Earth. The AM Broadcast Band gradiometer (AMG) receiver with its companion remote AM tower enable the dynamic gradiometer response measuring range to exceed sixty decibels .

Buried-utility-detection embodiments of the present invention also leverage special earth penetrating radars in the 100-MHz to 2,000-MHz range with special phase-coherent elimination of ground surface reflection noise of at least sixty decibels in digital signal processing with a field programmable gate array (FPGA) . For background, see United States Patent Application, Published Application US

2014/0125509 on May 8, 2014, filed Jan. 10, 2014 as serial number 14/152,823, and titled RADAR FOR REJECTING AND LOOKING PAST SURFACE REFLECTIONS, is incorporated herein by reference. Herein lies a first advantage of our electromagnetic gradiometers in this application, the radio energy used for detection of underground utility infrastructures travels only once through the overburden. Active radar from the surface, by its nature, forces the radio energy used for detection to travel twice through the overburden, e.g., down through the surface to a buried object, and then back up through the surface. Making radar only useful in imaging shallow depths. Conventional active radar also suffers from a "surface glare" of radio energy because the ground surface is very reflective to radar. Even more so if wet with puddles and dew. The surface reflection, unless suppressed, surely limits VHF/UHF band ground penetrating radar dynamic signal reflection measuring range.

The cylinder centerline, e.g., of a wire or pipe, will typically be nearby, down in the ground by tens of feet. So the gradiometric spatial measuring difference ( δ) in scattered magnetic field response will be measurable. The illuminating and scattered EM field components are always phase-coherent with respect to each other, and therefore synchronous radio detection methods are usefully employed.

Differences in the EM fields measured at different antenna locations ( δ) are related to the spatial gradient, differential, difference or derivative.

A vertical magnetic gradiometer (VMG) can usually be carried over a search area surface pretty easily by a motor vehicle or flown by a drown over a search area. The VMG has a spot of sensitivity which is oriented to stay nadir on the ground to the VMG itself. A Faraday shield surrounds each VMG antenna to screen out near-field electric dipole signals . A ferrite rod core and winding inside can then act as an antenna sensitive to only near-field magnetic dipole signals. Such magnetic dipole signals will radiate from nearby conductors if the conductors are in an electric radio field. The VMG on its vehicle calls on all the points in the search area to collect and measure the available magnetic signal gradients and reversals point-by-point . The points nadir to the VMG which coincide with buried conductors will express characteristic signatures in the signal gradients and phase reversals measurable in the VMG antenna . Even changes in the receiver ' s background noise will indicate important features in the soils .

Fig. 1 represents a near-surface vertical column of earth 102 occasionally topped with a land survey monument 103. For example, such a core would not exceed forty feet. Very often the goal in how deep to bury utilities and building

foundations is to get below the frost line in the soil so they don't freeze and don't heave in freeze-thaw cycles. Much deeper than that involves unnecessary expense.

A ground surface 104 has x-axis and y-axis dimensions in a survey area 106. This vertical column of earth 102 is abstracted in a z-axis (depth) and rendered in batch data processing later as a voxel in a false-color visual display apparatus of the present invention. Such is continually updated and improved with new bits of information as they are gathered from the field. For example the way Google Maps is a patchwork of many inputs from many sources over random time periods .

Embodiments of the present invention measure the search area in several dimensions, one is to measure the differences in magnitude at changing locations of an EMG antenna to observe spatial derivatives . Subsequent antenna locations yield more spatial derivatives . These derivatives are

subtracted to yield a local gradient and to suppress the far stronger planar wavefronts of the illuminating AM-Radio

Broadcasts. Conventional gradient-subtraction algorithms require many antenna receivers and phase coherency between them to suppress the illuminating EM-waves . Other measurement dimensions include shortwave radar, photography, and navigation fixes. One recent development of ours places neutron generators above ground on the surface over where plastic PVC pipes are suspected to lay. The piping is filled with N ₂ nitrogen gas if possible. When a neutron from the neutron generator strikes a nitrogen molecule, it will create an isotope with a very brief half-life. The chlorine molecules in the PVC pipe may also be struck with such

neutrons . When these nitrogen and/or chlorine isotopes decay they will emit gamma rays with energy signatures that can be detected and recognized by gamma ray detection equipment very common to the explosives detectors now in widespread use at airports and security checkpoints .

Toxic plume contamination can be detected by increases in the background noise (EM fields) that appears when scanning over abnormal zones . Earlier test observations later confirmed such readings to actually be the result of toxic plume

contamination. Toxic plume contaminations are conductive and electrically contrast with surrounding soils because anaerobic bacteria metabolic processes produce hydrogen sulfide, methane and enzymes. Non-uniform scattered wavefronts result and are detectable with gradiometric processing.

The AMG prototype was primarily capable of detecting axially-linear targets, and secondarily capable of detecting non-axially-linear zones of soil contamination. The EMG does detect gradients in soil contamination, but because non- linearity causes a rise in the noise floor over a contaminated zone where the contamination had raised the local soil conductivity .

As such, a detectable rise in RF background "noise" will be interpreted as soil contamination. Such soil contamination was not limited to hydrocarbon or other chemical contaminates . Any increase in water moisture properties in situ enhances ionization of clay-based soil and creates a home for

accumulation of anaerobic bacteria stains, effectively increasing the electrical conductivity and background RF "noise" over these "wet" zones. Background RF "noise"

increases are seen across all gradients, but they are more pronounced in the mid to deep looking gradients .

The image processing algorithms for the EMG prototype process data sets into one of three categories. The imaging software did not operate on the phase of the gradients, only their magnitudes. An "MAG" imaging process operated on the magnitude of the gradients . It took the highest and lowest amplitude signals from a set of data and did a linear

interpolation across the set, assigning colors for visual display. A "SmallMag" imaging process took a set of data, removed the highest amplitude data, and then interpolated the remaining data to span full-scale. The process removed large peaks in the data and highly emphasized small/weak signals . A "CMBD" imaging process combined the other two processes. It removed the large peaks, amplified the weak signals, then re ^¬ inserted the large peaks . This process worked good for contaminated soil analysis.

Regardless of which imaging form was selected, the rendered data sets were then color coded relative to the processed magnitude of individual gradient set being worked with. The color scale ranges used ran from from deep blue to intense red. The deeper blue color represented the smaller magnitude gradients, meaning nothing was detected. Intense red represented a maximum in gradient amplitudes, indicating a target was detected. Color blends in between were proportional the value of the gradient magnitude at that position,

depending on the strength of the signal from a nearby target. The form of imaging used in the EMG prototype was not designed to predict target depths.

Fig. 2 represents a data collection method 200 in which a data collection vehicle 202 transects over a ground surface 204 of a survey area with a single land survey monument 205. The data collection vehicle 202 is outfitted with several sensors, e.g., a GPS navigation receiver 206, a downward pointing digital camera 208 that visually registers human recognizable features like the land survey monument 205, a ground-penetrating radar (GPR) 210, and an electro-magnetic gradiometer (EMG) 212. A very full description of a suitable GPR for use here will be found in our recently allowed United States Patent Application published as US 2014/0125509, on May 8, 2014, and titled RADAR FOR REJECTING AND LOOKING PAST SURFACE REFLECTIONS. Such Application is a parent to this continuation-in-part, and is incorporated herein in full by reference. A very full description of a suitable EMG for use here will also be found in our United States Patent

Applications: (1) published as US 2014/0139224, on May 22, 2014, and titled STRAY WIRE LOCATION SENSOR; and, (2)

published as US 2014/0368196, on Dec. 18, 2014, and titled PRACTICAL ELECTROMAGNETIC GRADIOMETER. Such Applications too are parents to this continuation-in-part, and are each incorporated herein in full by reference.

Sensors 206, 208, 210, and 212 are simultaneously operated point-by-point in a search area to obtain their respective data outputs for each point on surface 204 that data collection vehicle 202 visits in a survey. The method objective is to locate by sensing, and map by combination of their outputs, the depths and locations of pipes, conduits, wires, structures, and other buried objects 214 beneath surface 204. A local AM-Radio Broadcast Station 220 outside the search area is depended upon to radiate a strong long- wavelength radio carrier 222 in the 500-kHz to 1-MHz band. Such local AM-Radio Broadcast Station 220 being nearby is serendipitous. Buried objects 214 will capture some of this radio energy and re-radiate electromagnetic signals 224 and 226. These are respectively sensed as magnetic gradients by EMG 212.

GPR 210 operates by sending radio signals 230 in the middle frequencies of 100-MHz to 2,000-MHz into the surface

204. A very strong radio reflection 232 always occurs from the surface. But some of the energy 230 that does penetrate will be returned from buried objects 214. The strong surface reflections 232 are suppressed in signal processing in accordance with our disclosures in Published United States

Patent Application US 2014/0125509, May 8, 2014, titled RADAR FOR REJECTING AND LOOKING PAST SURFACE REFLECTIONS, and our other issued patents.

Fig. 3 represents how a large search area 300, like a city airport or the whole city itself, can be visually rendered as a map with overlays on a display screen bit by bit, point-by-point, using embodiments of the present

invention. Such large search area 300 is, in one regard, a mosaic of tiles, such as composite tiles 116-119 (Fig. 1) . A single land survey monument 301 occurs in at least one part and serves as a precise reference for the whole.

There will be tiles representing locations that-have- been-visited 302 and those next-to-be-measured 304. Stacked tile information 306 includes GPS position fixes and photographic surface location fixes and is communicated by a link 308 and collected by a database 310. An image processing algorithm 312 renders the whole visually to a display screen 314. For example, FALCONVIEW™ and SKYVIEW™ by the Georgia Tech Research Institute would be useful . Even partially rendered, display screen 314 will provide important information to construction and utility workers about the buried

infrastructures underlying area 300.

Figs . 4A and 4B represent how a horizontal-type magnetic dipole antenna 401 and a vertical-type magnetic dipole antenna 402 respectively respond with an EMG receiver and processor to a buried object 403 that is re-radiating radio energy from a local AM-Broadcast carrier. A waveform 411 in Fig. 4A results from the EMG receiver as horizontal-type magnetic dipole antenna 401 is moved left and right laterally overhead to buried object 403. A waveform 412 in Fig. 4B results from its EMG receiver when vertical-type magnetic dipole antenna 402 is moved left and right laterally overhead relative to buried object 403. The lateral distance (G) that either antenna 401 or 402 must be moved to change between a peak and a null in

EMG receiver waveforms 411 and 412 is approximate to the depth the object 403 is buried below the surface. It is therefore important to have very fine position fixes on antennas 401 and 402 at the instants they provide gradient waveforms 411 and 412. The position fixes provided by ordinary GPS receivers is usually not good enough without being assisted by photographic registrations of the ground surface at those same instants.

Fig. 5 represents a ground vehicle application 500 in which six VMG ' s 502-507 are carried in two single-file arrays, one array on each side of a vehicle. These two VMG arrays are hung out on flip-down outriggers so that their ground nadirs 509-514 will run along the shoulders of a roadway 516. Pipes and wires 520 are illustrated here as an example, and for purposes of discussion here is shown to come from off one side of roadway 516 and to terminate about in the middle. Such wires can easily be 100-300 feet in length. The end point of such wires will uniquely radiate a spherically spreading pattern, while the rest of the wire will radiate a

cylindrically spreading pattern. Precise end-point

determinations will look for this transition.

It should be obvious that VMG ' s 502-504 on the "wrong side" will not pass over pipes, wires 520 and therefore have little chance of detecting it. However, VMG ' s 505-507 on the "right" side will pass over, one at a time beginning with VMG 505 and quickly ending with VMG 507. So, if VMG ' s 502-507 are connected to a suitable signal processor while the vehicle carrying them is in forward motion, detection "blips" will occur in a string in VMG ' s 505-507, and none at the same time for VMG ' s 502-504. Wires that end under roadway 516 are of particular interest, and so they must be positively identified if stumbled upon.

It will usually be only the electric field component of the primary electromagnetic wave that can reach far enough to illuminate and induce significant current flow in surface and subsurface conductors . Such current flows cause cylindrically spreading secondary waves to propagate out over the

conductors ' length and are readily observable on and above the surface. These secondary waves will decay with the one-half power of distance from the radiating conductor.

Electromagnetic surveys of the observables using magnetic dipole antennas will reveal the orientation, depths, and locations of infrastructures and networks otherwise hidden or not apparent .

The characteristics of the things radiating the secondary waves can be inferred by measuring the magnitudes,

orientations, and phases of the secondary waves as they are received at various points on and above the ground surface. A difference in measurement between two identical receiving antennas, or two different measuring locations of a moving antenna, can be plotted as a gradient. Embodiments of the present invention take measurements from the same antennas at different points in a survey area.

In the far-field the primary wave exhibits a traveling plane-wavefront with electric and magnetic fields that travels directly from the transmitter to the receiver location.

Differential gradiometer antenna response rejected plane- wavefront EM-fields by the way the receiving magnetic antennas are constructed. The near-field cylindrical wavefront re- radiated (scattered) magnetic gradients can then be measured without interference (reduction in dynamic measuring range) from far-field plane-wavefront signals . .

Gradient measurement devices are able to resolve much finer electronic details than can total field measurement devices. As the antennas and receiver pass over radiating conductive targets during a typical gradiometer survey of an area, many dips and peaks in the secondary wave magnitudes, and phase shifts and reversals will be observed. A total field measurement for the same area can appear as a homogeneous blur without any details . Small changes in the gradient fields will not look important in total field measurements. Gradient measurement receivers can be configured to naturally reject interfering, unwanted signals .

More recent advancements by our research in gradiometer technology have shown that single vertical magnetic dipole antennas (VMD) or magnetic field sensors can provide useful, detailed information about the presence and nature of wires, pipes, and other surface and subsurface conductors.

There are at least three practical ways to move a gradiometer platform over the ground surface: (a) handheld, (b) on a ground vehicle, or (c) on a low-flying helicopter or drone airframes . Ground vehicles are better with larger power demands, heavier weights, and larger sizes. But all can benefit by reducing weight and power demands .

Ground vehicles, especially small ones, can jostle and bounce the receiving antennas so much that the gradiometer measurements suffer from changing noise floors. Airframes have minimum flying heights that can demand too much separation distance, and the secondary waves are, as a consequence, too faint to be detectable. The EMG have real-time electronic platform orientation compensation designed to correct

gradiometer response for flight or transect jostle.

The present invention includes extending Google Maps type application program interfaces (API's), or Google Maps itself, into being able to zoom in far enough to detail the buried utility infrastructure. Far enough in to see the details to safely guide digging.

Fig. 6 represents a video image 600 that is displayable on a user's mobile device. Video image 600 is a composite of several sub-images that are independently collected, oriented, scaled, and registered electronically to visually fit with one another. Each such sub-image can be deleted or dimmed in composite video image 600 by the user to help focus on particular aspects and features of interest in the mobile device display.

A satellite image 601 is a portion of a long-distance photograph taken by a satellite that passed miles above over a subject area sometime in the recent past. But due to its very nature, such images can be out-of-date by even a year or two.

A street maps layer 602 allows addresses to be found and streets to be navigated by cars, is an image familiar to Google Maps users. This street maps layer 602 is alternatively displayed with the satellite image 601. A recent addition to Google Maps is a building image layer (e.g., 603) that outlines the footprints of commercial and residential

buildings, and such can be included herein as well. A close-in surface photograph 604 is obtained from low altitudes to show surface details a pedestrian would recognize and be able to use to orient work crews .

A survey monuments layer 605 provides reference locations in the display for survey monuments that are with a current field-of-view .

A ground penetrating radar (GPR) rendering 606 results from tomographic processing of dozens, hundreds, or even thousands of field surveys with GPR equipment as represented in Fig. 2.

An EMG rendering 607 results from tomographic processing of dozens, hundreds, or even thousands of field surveys with EMG equipment as represented in Fig. 2.

A layer 608 introduces icon, legends, and info boxes to help a user understand what is being presented in display 600.

A construction drawings layer 609 permits as-built drawings to be overlaid for their information value or comparisons with in field measurements .

Fig. 7 represents a typical mine shaft or tunnel 702 filled with humid air 704 that has been dug into a moist soil 706. A condensation pool 708 is a common occurrence all along the floors of mine shafts and tunnels 702. The humidity in air 704 will typically sweat onto the walls and drip into

condensation pools 708. A naturally forming anaerobic bacteria coating 710 will thicken and spread over time.

Fig. 7 also includes a PVC or other plastic pipe 720 buried in moist soils 706. The moisture in the soils typically condenses on the outside walls of PVC pip 720 to fully cover its length and circumference with a naturally forming

anaerobic bacteria coating 722.

Condensed moisture that stays stagnant long enough in the absence of oxygen will create a habitat for anaerobic bacteria that will coat the outsides of pipes and the insides of tunnels buried in moist soils . Such anaerobic bacteria will excrete conductive compounds in coatings that can absorb, reflect, and reradiate radio energy. (But not near as well as metal pipes and wires do . )

Anaerobic processes strip electrons form organic carbon, hydrocarbon, and other elements and non-soluble ions that form in conductive pools . Anaerobic bacteria create mobile

electrons, cations and anions. When moisture disassociates from clay soil calcium ions forms an electromagnetically detectable coating on plastic pipe and in leakage plumes along pipelines and utilities . Local AM Radio Broadcast band electric fields are strong enough underground in the soils to cause mobile charges to accelerate and re-radiate.

A remarkable benefit of the very high detection

sensitivity of the EMG (Fig. 2, 5A, 5B, 6) is the material deposits resulting from their anaerobic bacteria methylation processes can be electronically sensed and imaged. Such deposits will naturally form inside tunnels, and outside around pipes, tanks, and vaults. Importantly, such deposits will coat plastic materials. These pipes, tanks, and vaults are thus naturally provided over time with conductive halos and shadows that an EMG can "see".

However, the EMG is so sensitive it will see the

anaerobic deposits in the soils that form on both manmade equipment like pipes and wires, and natural features. A discriminator is needed that will sort the resulting

tomographic images . Manmade equipment has the characteristic of straight lines and right angles . Natural features meander, undulate, and can be broken and disjointed.

Natural buried features surrounded with these conductive halos and shadows will not have the straight runs of constant depth that man-made infrastructure always has . And so that is a basis for filtering and discrimination in tomography.

Fig. 8 represents a method of underground utility location and damage prevention 800 that builds visual multi- layer composites of drawings, photographs, and sensor images from independently obtained representations and electronic scans of underground and surface features. Such scans are mutually registered and scaled to fit one another so they stack correctly.

An important source of information is existing data 802 that includes construction company as-built drawings 804.

A step 806 orients, scales, registers, and otherwise builds a first image layer from a surface photograph 808 applied in a step 810 to a map with a standardized orientation and scale of a land surface including in an immediate search area from a zenith point in space above.

A step 812 orients, scales, registers, and otherwise builds a second image layer from a tomographic rendering from a number of electromagnetic gradiometer (EMG) scans 814 onto the standardized orientation and scale of the map. EMG scans provide amplitude 816 and phase 818 measurements that are so sensitive as to show the conductive coating outlines of anaerobic bacterial activity around both natural and manmade objects in the ground. So step 814 further discriminates between the two after rendering in tomography and filters out natural object outlines based on their silhouettes and profiles. For example, outlines of natural objects meander side-to-side and undulate in depth, such as tree roots .

Manmade objects tend to run in straight lines at constant depths, such as pipes and cables do in trenches.

The results of an EMG investigation of buried objects point-by-point in the immediate search area of a corresponding ground surface can be radio-illuminated by electro-magnetic radio energy from a radio broadcast transmitter generally in the 500-kHz to 1,000-kHz band transmitting from a location outside the immediate search area.

A step 820 orients, scales, registers, and otherwise builds a third image layer onto the standardized orientation and scale of the first and second images with tomographic renderings 822 of ground penetrating radar (GPR) surface-based measurements of short-wavelength radio reflections of 100-MHz to 2,000-MHz returned by buried-objects in the immediate search area using a phase-coherent elimination 824 of ground surface reflection noise of at least sixty decibels in digital signal processing.

A step 826 orients, scales, registers, and otherwise builds a fourth image layer to the standardized orientation and scale on the first through third image layers an

interpretation 828 of signals and a display of icons 830 and characteristic descriptions of underground utility

infrastructures in the immediate search area.

A step 832 registers and overlays all other layers together in a global positioning system (GPS) depiction 834 of the land surface and coordinates 836 that includes the first through fourth image layers .

The result is underground buried objects and utilities are located in visual multi-layer composite display 838 that can guide safe digging nearby in the immediate search area.

The EMG response to AM radio broadcast transmitter induced secondary radiation from subsurface pipelines and utilities is more than thirty-two times (30-dB) greater than the surface radio interference noise and the AM radio

broadcast signal itself. These very high EMG detection sensitivity thresholds increase detection probability and confidence. The EMG response has characteristics that indicate a utility burial depth, a material size. Tomography image processing reveals the utility track lines in the digital subsurface of earth maps .

Both EMG magnetic amplitude and EMG magnetic phase coherence measurements of secondary electromagnetic radiations of any conductive deposits left by past anaerobic bacteria activity amongst the buried objects. The magnetic phase coherence measurements are far more sensitive in detection than the magnetic amplitude measurements. Filtering in tomography and not including any magnetic phase coherence measurements that outline non-linear or non-orthogonal tracks in any dimension, wherein such are interpreted to be naturally occurring features and not made-made utility infrastructure. Magnetic gradients are far more sensitive to non-metallic (plastic) pipe.

So, alternative embodiments discriminate between the tomographic results of EMG magnetic amplitude and magnetic phase coherence measurements of secondary electromagnetic radiations . Some will outline non-linear or non-orthogonal tracks in one or more dimensions, and such are machine interpreted by artificial intelligence (AI) methods to be naturally occurring features and not made-made utility infrastructure .

Underground utility damage-prevention and location service companies as well as infrastructure owners can benefit from embodiments of the present invention in which a variety of platforms are used to mount and deploy EMG ' s in the field. EMG ' s mounted on city vehicles can be used to precisely map subsurface utilities as they go about their otherwise routine travels around the city. EMG ' s can pinpoint where roadbed moisture is accumulating (the incipient cause of potholes and other road-bed failures) . EMG ' s on Hovercraft can photograph surface features while locating all subsurface pipelines and utilities . Architectural engineering firms may use hovercraft and drone EMG platforms in design. Such platforms help automate audited and registered-monument "as-built" drawings as contractual exhibits and permeant records . Established locator companies will realize new business opportunities as contractor-deliverable AutoCAD utilities maps are audited- validated and become a matter-of-record . The matter-of-record data enables construction companies, pipeline and water utilities as owners to quickly respond to emergencies .

Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the "true" spirit and scope of the invention.

What is claimed is :