The present invention is related to a transmission device intended to be deployed above a treetop of a group of trees using an airborne platform.

The group of trees is notably a forest located in a region of interest with difficult ground access. The region in particular comprises a high density of vegetation, such as a tropical forest with a canopy. Also, the region may comprise rugged terrain such as hills (for example foothills), cliffs and/or mountains. Also, the region may comprise dangerous access areas, such as areas with unexploded ordinances (UXOs).

The transmission device is for example used in the framework of oil and gas geophysical exploration surveys. The seismic survey acquisition is one of the main geophysical methods carried out for exploration in oil and gas industry. The geophysical measurements obtained during such a survey are critical in building a subsurface image representative of the geology of the region of interest, in particular to determine the location of potential reservoirs of oil and gas.

Such a seismic survey is for example conducted by deploying seismic sources and seismic receivers, such as geophones, on the ground of the region of interest. The seismic receivers are able to record mainly the reflections of the seismic waves produced by the seismic sources on the different layers of the earth in order to build an image of the subsurface.

The seismic survey generally requires sources and a large amount of seismic receivers on the ground at various locations, along generally several profiles to create dense arrays of seismic sources and seismic receivers.

Placing seismic sources and seismic receivers in a remote region of interest may be a tedious, dangerous and expensive process. In particular, when the region is barely accessible, such as in a tropical forest and/or in a region with uneven terrain and/or in a region with UXOs, the seismic sources and the seismic receivers have to be carried at least partially by foot by teams of operators. In many cases, clearings have to be opened in the forest to place on the ground the relevant equipment and allow the movements of the operators. Then, trails have to be cleared in the forest to deploy the seismic receivers.

These tasks create a strong environmental impact in the region of interest and may induce significant health and safety risks for operators, especially during the setting-up of the seismic receivers and of the seismic sources.

The set-up of the seismic receivers and/or the seismic sources on the ground is an extensive process which requires drilling the ground, and in the case of the seismic receivers, ensuring that the coupling between the seismic receiver and the ground is adequate.

A way for setting up the seismic receivers consists in using a flying vehicle such as an unmanned aerial vehicle. The flying vehicle is flown above the location at which the seismic receiver should be implanted in a dropping area. Then, the seismic receivers are successively dropped from the flying vehicle and fall to the ground.

Each seismic receiver comprises a transmitter/receiver device able to receive instructions signal from a remotely located base camp intended to control the seismic acquisition, and able to transmit seismic data recorded during the seismic acquisition, to the base camp.

To ensure efficiently transmission and reception between the seismic receivers and the base camp, backhaul radio towers fixed to the ground of the region of interest are required to relay the signals between the seismic receivers and the base camp.

However, as mentioned before, the installation of numerous backhaul radio towers is tedious and dangerous and has a strong impact on the environment. Moreover, the quality of the radio covering is not totally ensured and adding a novel backhaul radio tower, not initially planned, may result in delays. Besides, the vegetation density, especially in tropical forest, degrades the quality of communication between the seismic receivers located in the ground and the backhaul radio towers and/or the base camp.

One aim of the invention is to provide a transmission device which is easy, safe and flexible to install, and which does not have a strong environmental impact on the group of trees.

To this aim, the subject-matter of the invention is a transmission device intended to be deployed above a treetop of a group of trees using an airborne platform, the transmission device comprising:

- an anchorage system intended to be borne by the treetop,

- a first transmitting/receiving unit fixed to the anchorage system intended to receive a first signal received from below the treetop, and/or to transmit a second signal, received from above the treetop, below the treetop,

- a second transmitting/receiving unit fixed to the anchorage system intended to receive the first signal from the first transmitting/receiving unit and to transmit said signal above the treetop, and/or intended to transmit the second signal to the first transmitting/receiving unit,

the first transmitting/receiving unit and the second transmitting/receiving unit being vertically offset and the second transmitting/receiving unit being disposed above the anchorage system, when said anchorage system is borne by the treetop. The transmission device according to the invention may comprise one or more of the following features, taken solely or according to any potential technical combination:

- the first transmitting/receiving unit and the second transmitting/receiving unit are respectively located below the anchorage system and above the anchorage system;

- at least one of the first transmitting/receiving unit and the second transmitting/receiving unit is fixed on the anchorage system;

- the first transmitting/receiving unit and the second transmitting/receiving unit are connected through a wireline;

- the transmission device further comprises an upper mast, preferably a rigid upper mast, the upper mast being fixed to the anchorage system, extending above the anchorage system in a direction substantially perpendicular to the anchorage system, the second transmitting/receiving unit being fixed to the upper mast;

- the upper mast is telescopic;

- the transmission device further comprises a sun protective shield disposed above the second transmitting/receiving unit;

- the transmission device further comprises a lifting device, intended to be fixed to an airborne platform, to carry the transmission device with the airborne platform;

- the anchorage system is movable between a folded configuration and an unfolded configuration wherein the anchorage system is borne by the treetop;

- the transmission device further comprises at least one photovoltaic panel fixed to the anchorage system;

- the anchorage system comprises at least one anchorage element, the anchorage element comprising a rigid structure or a semi-rigid structure and a netting fixed to said structure;

- the transmission device further comprises a lower mast, preferably a flexible lower mast, fixed to the anchorage system, extending below the anchorage system in a direction substantially perpendicular to the anchorage system, the first transmitting/receiving unit being fixed to the lower mast, preferably at a lower end of the lower mast;

- the transmission device further comprises at least a battery pack connected to the first transmitting/receiving unit and to the second transmitting/receiving unit;

- the battery pack is fixed to the lower mast or onto the anchorage system;

- the transmission device further comprises a slowing device intended to decrease the vertical speed of the transmission device when dropped from an airborne platform.

The invention also relates to a telecommunication device comprising: - at least one auxiliary transmitting/receiving unit intended to be deployed under a treetop,

- at least one transmission device as described above, intended to be deployed in the vicinity of the auxiliary transmitting/receiving unit,

- at least one primary transmitting/receiving unit, intended to be deployed remotely from the transmission device.

Moreover, the invention relates to a method for installing a transmission device as described above, above a treetop using an airborne platform, the transmission device being removably fixed to the airborne platform, the method comprising:

- positioning the airborne platform above a ground target, above the treetop, and

- deploying the transmission device from the airborne platform for bearing the anchorage system in the treetop.

The method according to the invention may comprise one or more of the following features, taken solely or according to any potential technical combination:

- the deploying step comprises dropping the transmission device from the airborne platform by dissociating the transmission device from the airborne platform;

- the deploying step comprises laying the anchorage system of the transmission device on the treetop using the airborne platform and dissociating the transmission device from the airborne platform.

The invention also relates to a method for retrieving a transmission device as described, above a treetop, using an airborne platform, the transmission device being removably fixed to the airborne platform, the method comprising:

- positioning the airborne platform above the transmission device,

- fixing the transmission device to the airborne platform, and

- carrying the transmission device with the airborne platform.

The invention is also related to a use of a telecommunication device as described above, comprising:

- deploying the auxiliary transmitting/receiving unit under the treetop, the transmission device according to the method described above, the primary transmitting/receiving unit remotely from the transmission device,

- transmitting the first signal from the auxiliary transmitting/receiving unit to the first transmitting/receiving unit of the transmission device,

- transmitting the first signal from the first transmitting/receiving unit of the transmission device to the second transmitting/receiving unit of the transmission device,

- transmitting the first signal from the second transmitting/receiving unit of the transmission device to the primary transmitting/receiving unit. The use according to the invention may comprise one or more of the following features, taken solely or according to any potential technical combination:

- the use further comprises:

- transmitting the second signal from the primary transmitting/receiving unit to the second transmitting/receiving unit of the transmission device,

- transmitting the second signal from the second transmitting/receiving unit of the transmission device to the first transmitting/receiving unit of the transmission device,

- transmitting the second signal from the first transmitting/receiving unit of the transmission device to the auxiliary transmitting/receiving unit;

- the use further comprises an intermediate step for receiving the first signal from the second transmitting/receiving unit to a backhaul radio tower, said backhaul radio tower transmitting the first signal to the primary transmitting/receiving unit, or for receiving the second signal from the primary transmitting/receiving unit and transmitting the second signal to the second transmitting/receiving unit of the transmission device.

The invention will be better understood, based on the following description, given solely as an example, and made in reference to the following drawings, in which:

- figure 1 is a view of a transmission device according to a first embodiment of the invention,

- figure 2 is a view of the transmission device of figure 1 carried by an airborne platform over a treetop of a forest,

- figure 3 is a view of a telecommunication system according to the invention,

- figure 4 is a detail of the lower part of the transmission device of figure 1 , and

- figures 5 to 7 are views of various embodiments of the invention.

A transmission device 10 according to the invention is represented in figure 1 .

The transmission device 10 is intended to be deployed above a treetop 12 of a group of trees 14 using an airborne platform 16, as represented in figures 2 and 3.

The group of trees 14 is for example a tropical forest with high density vegetation comprising trees 18 forming a canopy 20 which covers a majority of the surface of the ground 22.

The forest 14 is notably located in a region of interest with difficult access, resulting of the high density vegetation and/or of uneven terrain. For example, the region of interest comprises hills, mountains, cliffs or any type of rugged terrain. The region of interest is for example located on foothills. As schematically represented in figure 2, the airborne platform 16 is advantageously a helicopter. In variant, the airborne platform 16 is an unmanned aerial vehicle (UAV), a plane or an airship.

The subsurface located below the ground 22 comprises layers of geological formation 24 and potentially oil and gas reservoirs 26.

A seismic survey may be used to locate such oil and gas reservoirs 26.

The seismic survey is a geophysical survey which comprises collecting geophysical measurements for determining physical properties of the subsurface located in the region of interest and/or for building an image of the subsurface, preferably a tridimensional image of the subsurface based on the processing of the collected measurements.

The physical properties are typically the density and/or the wave velocities of the layers of geological formation 24.

The method comprises measuring the vibrations induced in a subsurface of the area of interest by the seismic sources with a plurality of seismic receivers 28, for example visible in figure 3.

Each seismic source is able to generate waves which propagate in the subsurface and reflect at the interfaces of the layers of geological formation 24.

The seismic source for example comprises an explosive, in particular dynamite, able to generate waves in the ground.

The seismic source is typically inserted in a hole drilled into the ground, for example at a depth comprised between 0 meter and 100 meters, preferably between 5 meters and 80 meters.

For example, the hole is drilled using an unmanned ground vehicle such as a semi automatic drilling platform.

In a variant, the seismic source comprises a mechanical device such as a hammer, a vibrator...

The area of interest comprises at least one base camp 30 (figure 3). Each base camp 30 comprises for example a facilities adapted to house operators during the seismic survey and equipment for the seismic survey. The base camp 30 comprises a helipad and is typically used for management of the take-off and the landing.

The base camp 30 may be used for first aid (e.g. medevac).

Each base camp 30 typically comprises a collection and/or analysis unit for collecting and/or analyzing seismic data measured by the seismic receivers 28.

Advantageously, the area of interest comprises a plurality of base camps 30 spread in the whole surface of the area of interest. Advantageously, the area of interest comprises a main camp (not represented). The main camp is the headquarter camp which controls the deployment and the acquisition of the seismic survey.

Each seismic receiver 28 is able to record the waves generated by each seismic source and the reflected waves at the interfaces of the layers of geological formation 24.

The seismic receiver 28 is for example a geophone able to measure the velocity of the direct and reflected waves.

Advantageously, the seismic receiver 28 comprises at least one geophone, in particular three geophones and/or an accelerometer.

In a variant, the seismic receiver 28 comprises a distributed acoustic sensing (DAS) or a distributed vibration sensing (DVS) using fiber optic cables.

Each seismic receiver 28 is partially introduced in the ground 22 so as to ensure a functional coupling with the ground 22.

Advantageously, the seismic receivers 28 are transported to their locations and dropped in the ground from airborne platforms.

The airborne platforms typically take off from a base camp 30.

For example, the airborne platform is a UAV.

Each seismic receiver 28 has for example the shape of a dart adapted to be introduced in the ground 22, as visible in figure 3. In a variant, the seismic receivers 28 has the shape of a ball or/and a parallel pipe shape.

Each seismic receiver 28 comprises an auxiliary transmitting/receiving unit 32 intended to receive/transmit signal from/to a primary transmitting/receiving device 34, for example located in a base camp 30, and/or from/to a transmission device 10 according to the invention.

As represented in figure 1 , the transmission device 10 according to the invention comprises an anchorage system 36, a first transmitting/receiving unit 38 and a second transmitting/receiving unit 40 both fixed to the anchorage system 36.

The anchorage system 36 is intended to be borne by the treetop 12, as represented in figure 3.

Preferentially, the anchorage system 36 is flat.

For example, the anchorage system 36 comprises several anchorage elements 42, for example four anchorage elements 42, as represented in figure 1. Each anchorage element 42 comprises a rigid structure 44 and a netting 46 fixed to the structure 44.

Advantageously, the anchorage elements 42 are regularly spread, in particular are disposed symmetrically in order to improve the stabilization of the transmission device 10 in the treetop 12. The total surface of the anchorage system 36 depends on the vegetation density of the forest 14.

The total surface of the anchorage system 36 is preferentially comprised between 5 m ² and 150 m ² , for example 30m ² , particularly for a tropical forest. This ensures a stable anchorage of the transmission device 10 above the treetop 12.

In a variant (not shown), the anchorage system 36 has a polygonal shape, such as hexagonal or octagonal shape.

Preferably, the structure 44 is made with light material such as carbon.

In a variant, the structure 44 is semi-rigid, for example an inflatable structure.

Both features allow providing a light structure 44 easy to carry with the airborne platform 16.

The netting 46 is preferably a polyamide high-tension netting. This ensures a good robustness of the anchorage system 36.

In variant, the netting 46 is biodegradable polymer high-tension netting or a plastic high-tension netting.

Advantageously, the anchorage system 36 is movable between a folded configuration for transportation of the anchorage system 36 to its use position, and a deployed unfolded configuration wherein the anchorage system 36 is borne by the treetop 12. The folded configuration is advantageously used during the carrying of the transmission device 10 to limit the wind surface area.

In a variant (not represented), the anchorage system 36 comprise an arch structure.

Advantageously, the transmission device 10 comprises at least one photovoltaic panel 48 fixed to the anchorage system 36.

The photovoltaic panel 48 is typically fixed on the surface of at least one anchorage element 42.

The photovoltaic panel 48 allows transforming sun light into electricity intended to power the transmission device 10, in particular the first transmitting/receiving unit 38 and the second transmitting/receiving unit 40.

In a variant (not shown), the surface of the anchorage system 36 is covered by a photovoltaic textile. Photovoltaic textiles comprise photovoltaic cells which are directly integrated in the textile during manufacturing.

In variant or in addition, the surface of the anchorage system 36 comprises at least one wind energy harvesting element such as a wind turbine. In another variant or in addition, the surface of the anchorage system 36 comprises at least one element for collecting energy generated by vibrations of the anchorage system 36, for example a piezo electric element.

The use of photovoltaic textiles is particular advantageous since it allows maximizing the photovoltaic surface exposed to the sun light. It is also more robust compared to classical rigid photovoltaic panels.

The first transmitting/receiving unit 38 is intended to receive a first signal received from below the treetop 12, and/or to transmit a second signal, received from above the treetop 12, below the treetop 12.

The first signal is for example emitted by the auxiliary transmitting/receiving unit 32 of the seismic receiver 28. The first signal is then for example seismic data signal.

In variant or in complement, the first signal is emitted by a hand-held portable two- way radio transceiver such as a walkie-talkie hold by a crew member progressing in the region of interest, or by a portable phone, or by a personal tracker of the crew member (not represented). The first signal is then for example voice data signal. By tracking the first signal with at least three transmission devices 10, the crew member may be easily located.

In variant or in complement, the first signal is emitted by at least one additional geophysical sensor disposed on or in the ground of the region of interest (not represented). The first signal is then geophysical data signal.

The additional geophysical sensor measures at least a physical parameter of the ground. For example, the additional geophysical sensor is a magnetotelluric sensor which measures the natural geomagnetic and/or geoelectric field variation on the surface of the ground.

In variant or in complement, the first signal is a signal emitting by a detecting device, such as a visible or infrared video camera or a thermic sensor device, fixed to the transmission device 10, and intended to detect the presence of human and/or animals in the vicinity of the transmission device 10.

The second signal is for example a control signal intended to start the data acquisition of the seismic sensor 28.

In variant or in complement, the second signal is voice data signal emitted from the primary transmitting/receiving device unit 34.

As represented in figure 1 , the transmission device advantageously comprises a lower mast 50 fixed to the anchorage system 36.

The lower mast 50 is preferably fixed in the center of the anchorage system 36.

Preferably, the lower mast 50 is flexible. Preferably, the lower mast 50 has a length comprised between 5 m and 15 m, for example between 7 m and 10 m.

When the transmission device 10 is borne by the treetop 12, the lower mast 50 extends below the anchorage system 36 in a direction substantially perpendicular to the anchorage system 36.

The transmission device 10 also advantageously comprises an upper mast 52 fixed to the anchorage system 36.

Similarly to the lower mast 50, the upper mast 52 is preferably fixed in the center of the anchorage system 36.

Preferably, the upper mast 52 is rigid.

The upper mast 52 extends above the anchorage system 36 in a direction substantially perpendicular to the anchorage system 36, when the transmission device 10 is borne by the treetop 12.

Preferably, the upper mast 52 has a length comprised between 5 m and 15 m, for example between 7 m and 10 m.

The first transmitting/receiving unit 38 and the second transmitting/receiving unit 40 are vertically offset.

The first transmitting/receiving unit 38 and the second transmitting/receiving unit 40 are preferably connected through a wireline 54.

The first transmitting/receiving unit 38 is fixed to the lower mast 50, preferably at a lower end of the lower mast 50. The first transmitting/receiving unit 38 acts as a ballast and ensures a good stability of the transmission device 10 when borne by the treetop 12.

The first transmitting/receiving unit 38 is then hung in the forest 14. The first transmitting/receiving unit 38 does not touch the ground 22.

As more particularly visible in figure 4, the first transmitting/receiving unit 38 comprises at least one antenna 56, at least one seismic receiver controller 58 and at least one master seismic receiver controller 60.

The antenna 56 complies with the chosen channel access method such as but not limited to TDMA (time division multiple access), FDMA (frequency division multiple access), CDMA (code division multiple access)...

Advantageously, the antenna 56 allows an omnidirectional covering. The antenna 56 may be a single omnidirectional antenna, or several antennas having an overlap in their radiating pattern to allow omnidirectional covering.

The vertical beam width is as wide as possible in order to manage with the steep elevation changes of the region of interest. For example, the vertical beam width is comprised between 0° and 180° . For example, each antenna 56 supports frequencies in the ISM (Industrial, Scientific and Medical) band such as the 433 MHz, 900 MHz, and 2.4 GHz bands.

As represented in figure 4, the first transmitting/receiving unit 38 comprises four seismic receiver controllers 58. One of the four seismic receiver controllers 58 is also a master seismic receiver controller 60.

Each of seismic receiver controllers 58 and master seismic receiver controller 60 is intended to receive a signal from the second transmitting/receiving unit 40 and to transmit the signal to each seismic receiver 28, and is intended to receive a signal from each seismic receiver 28 and transmit the signal to the second transmitting/receiving unit 40.

The master seismic receiver controller 60 comprises protocol communication interface such as an Ethernet interface for transferring data to the second transmitting/receiving unit 40 and a power supply unit to superpose signal and power on the same link such as a Power over Ethernet (PoE) conversion power supply for passing electric power along with data signal on the communication cabling.

The power supply generates the necessary voltages and distributes power to the seismic receiver controllers 58.

The master seismic receiver controller 60 further comprises a timing GPS unit intended to time-stamp the received and/or transmitted signal.

The second transmitting/receiving unit 40 is fixed to the upper mast 52. Preferably, the second transmitting/receiving unit 40 is fixed at an upper end of the upper mast 52.

The second transmitting/receiving unit 40 is disposed above the anchorage system 36, when said anchorage system 36 is borne by the treetop 12.

The second transmitting/receiving unit 40 is intended to receive the first signal from the first transmitting/receiving unit 38 and to transmit said signal above the treetop 12, and/or intended to transmit the second signal to the first transmitting/receiving unit 38.

The second transmitting/receiving unit 40 comprises a plurality of antenna so as to ensure an omnidirectional coverage. For example, the second transmitting/receiving unit 40 comprises 10 antennas roundly disposed at 36° irtervals.

The second transmitting/receiving unit 40 comprises several radio devices operating at different frequencies intended to be used to remotely transmit and relay different types of data signal such as seismic data measured by the seismic receivers 28.

By using multiple frequency bands, the second transmitting/receiving unit 40 collects seismic data from seismic receivers 28 and in the same time is able to transmit aggregated data at high rates. Advantageously, the transmission device 10 comprises a sun protective shield (figure 1 ) disposed above the second transmitting/receiving unit 40 to protect the second transmitting/receiving unit 40 from the sun light and avoid overheating.

The transmission device 10 comprises at least one battery pack 64 connected to the first transmitting/receiving unit 38 and to the second transmitting/receiving unit 40 and/or to the photovoltaic panel 48.

Advantageously, the battery pack 64 is fixed to the lower mast 50.

Preferably, the battery pack 64 is fixed between the anchorage system 36 and the first transmitting/receiving unit 38, preferably closer to the first transmitting/receiving unit 38. In this way, similarly to the first transmitting/receiving unit 38, the battery pack 64 acts as ballast for the stability of the transmission device 10.

In a variant, the battery pack 64 is fixed onto the anchorage system 36.

Advantageously, the transmission device 10 comprises a data storage unit (not represented), such as a non-volatile memory such as a flashcard and/or a hard disk. The data storage unit is advantageously used as a buffer storage unit in case of data transmission issues. In variant, the data storage unit is used as backup copy of the transmitted data. In case of problem, the hard disk may be retrieved by a crew on the ground or by an airborne platform 16 with the transmission device 10.

The transmission device 10 comprises a lifting device 66, intended to be fixed to an airborne platform 16, to let the airborne platform 16 carry the transmission device 10.

The lifting device 66 is for example a hook or a ring.

The lifting device 66 is intended to be fixed to a sling of the airborne platform 16.

The lifting device 66 is removably fixed to the airborne platform 16.

Preferably, the lifting device 16 is disposed on the sun protective shield 60.

Advantageously, the lifting device 66 and the sun protective shield 60 are made in a single part.

The invention also relates a telecommunication system 68, as represented in figure 3. The telecommunication system 68 comprises at least one auxiliary transmitting/receiving unit 32 intended to be deployed under a treetop 12, as described above. The auxiliary transmitting/receiving unit 32 may be for example the auxiliary transmitting/receiving unit 32 of the seismic receiver 28 or a hand-held portable two-way radio transceiver.

The telecommunication system 68 further comprises at least one transmission device 10 as described above, intended to be deployed in the vicinity of the auxiliary transmitting/receiving unit 32. For example, the transmission device 10 is deployed at a distance comprised between 1 m and 10 km from the auxiliary transmitting/receiving unit 32 intended to communicate with the transmission device 10.

The telecommunication system 68 also comprises at least one primary transmitting/receiving unit 34, intended to be deployed remotely from the transmission device 10. For example, the primary transmitting/receiving unit 34 is located in a base camp 30. For example, the primary transmitting/receiving unit 34 is located at a distance comprised between 50 m and 30 km from a transmission device 10.

In a variant, the primary transmitting/receiving unit 34 is located in the main camp.

According to the embodiment represented in figure 3, the telecommunication system 68 further comprises at least one backhaul radio tower 70, preferably disposed in a clearing of the region of interest. The backhaul radio tower 70 relays the signal between the primary transmitting/receiving unit 34 and the transmission device 10.

A method for installing a transmission device 10 according to the invention above a treetop 12 using an airborne platform 16 is now described.

The method comprises positioning the airborne platform 16 above a ground target, above the treetop 12.

Then, the method comprises deploying the transmission device 10 from the airborne platform 16 for bearing the anchorage system 36 in the treetop 12.

Advantageously, the deploying step comprises dropping the transmission device 10 from the airborne platform 16 by removably dissociating the transmission device 10 from the airborne platform 16.

For example, the transmission device 10 is dropped from a height above the treetop 12 comprised between 1 m and 30 m.

A method for retrieving a transmission device 10 according to the invention is now described.

The method comprises positioning the airborne platform 16 above the transmission device 10 which is borne by the treetop 12. In this configuration, the upper mast 52, and more particularly the lifting device 66 is located above the treetop 12.

The method comprises removably fixing the transmission device 10 to the airborne platform 16 using the lifting device 66.

Then, the method comprises carrying the transmission device 10 with the airborne platform 16.

For example, the transmission device 10 may be carried to a base camp 30 for checking or to another ground target.

Finally, a use of the telecommunication system 68 as mentioned above is described. The use comprises deploying at least one auxiliary transmitting/receiving unit 32 under the treetop 12, at least one transmission device 10 according to the method for installing described above, using an airborne platform 16, and at least one primary transmitting/receiving unit 34 remotely from the transmission device 10.

The use comprises transmitting a first signal from the auxiliary transmitting/receiving unit 34 to the first transmitting/receiving unit 38 of the transmission device 10, transmitting the first signal from the first transmitting/receiving unit 38 of the transmission device 10 to the second transmitting/receiving unit 40 of the transmission device 10, and transmitting the first signal from the second transmitting/receiving unit 40 of the transmission device 10 to the primary transmitting/receiving unit 34.

The first signal is for example emitted by the auxiliary transmitting/receiving unit 32 of the seismic receiver 28. The first signal is then for example seismic data signal.

In variant or in complement, the first signal is emitted by a hand-held portable two- way radio transceiver such as a walkie-talkie hold by a crew member progressing in the region of interest, or by a portable phone, or by a personal tracker of the crew member (not represented). The first signal is then for example voice data signal. By tracking the first signal with at least three transmission devices 10, the crew member may be easily located.

In variant or in complement, the first signal is emitted by at least one additional geophysical sensor disposed on or in the ground of the region of interest (not represented). The first signal is then geophysical data signal.

In variant or in complement, the first signal is a signal emitting by a detecting device, such as a visible or infrared video camera or a thermic sensor device, fixed to the transmission device 10, and intended to detect the presence of human and/or animals in the vicinity of the transmission device 10.

Advantageously, the use comprises transmitting a second signal from the primary transmitting/receiving unit 34 to the second transmitting/receiving unit 40 of the transmission device 10, transmitting the second signal from the second transmitting/receiving unit 40 of the transmission device 10 to the first transmitting/receiving unit 38 of the transmission device 10, and transmitting the second signal from the first transmitting/receiving unit 38 of the transmission device 10 to the auxiliary transmitting/receiving unit 32.

The second signal is for example a control signal intended to start the data acquisition of the seismic sensor 28.

In variant or in complement, the second signal is voice data signal emitted from the primary transmitting/receiving device unit 34. In a variant, the telecommunication system 68 comprises at least one backhaul radio tower 70 and then, the use comprises an intermediate step for transmitting the first signal from the second transmitting/receiving unit 40 of the transmission device 10 to the backhaul radio tower 70 and transmitting the first signal from the backhaul radio tower 70 to the primary transmitting/receiving unit 34.

Respectively, the use may comprise a step for transmitting the second signal from the primary transmitting/receiving unit 34 to the backhaul radio tower 70, and transmitting the second signal from the backhaul radio tower 70 to the second transmitting/receiving unit 40 of the transmission device 10.

In a variant (not represented), the telecommunication system 68 comprises at least one airborne platform, the use comprises an intermediate step for transmitting the first signal from the second transmitting/receiving unit 40 of the transmission device 10 to the airborne platform, and transmitting the first signal from the airborne platform to the primary transmitting/receiving unit 34.

Respectively, the use may comprise a step for transmitting the second signal from the primary transmitting/receiving unit 34 to the airborne platform, and transmitting the second signal from the airborne platform to the second transmitting/receiving unit 40 of the transmission device 10.

The airborne platform is for example a UAV, an airship or a helicopter.

Figures 5 to 7 present other embodiments of the transmission device 10 according to the invention. The embodiments are described by differences/additions relative the first embodiment described above.

According to the embodiment of figure 5, the upper mast 52 is telescopic. The upper mast 52 is advantageously extended when the transmission device 10 is born by the treetop 12. Then, the height of the upper mast 52 may be adjusted to optimize the transmission of the signal and the wind surface area. The upper mast 52 is advantageously collapsed during the carrying of the transmission device 10 by the airborne platform 16 to reduce the wind surface area. The upper mast 52 may be actuated using for example a motor.

According to the embodiment of figure 6, the transmission device 10 comprises a slowing device 72 intended to decrease the vertical speed of the transmission device 10 when dropped from the airborne platform 16. The slowing device 72 comprises at least one parachute fixed to the anchorage system 36 and/or to the upper mast 52 and/or to the sun protective shield 60, as represented in figure 6. Then, the method for installing the transmission device 10 comprises, after the dropping step, deploying the slowing device 72 to decrease the vertical speed of the transmission device 10 during the dropping.

According to the embodiment of figure 7, the transmission device 10 does not comprise an upper mast 52 and the second transmitting/receiving unit 40 is fixed directly on the anchorage system 36.

In this embodiment, the battery pack 64 is also preferably fixed on the anchorage system 36. The transmission device may also comprise a slowing device 72 (not represented) fixed to the anchorage system 36.

In variant of the invention, the transmission device 10 is not dropped from the airborne platform 16. The method for installing a transmission device comprises laying the anchorage system of the transmission device on the treetop using the airborne platform and dissociating the transmission device from the airborne platform.

The transmission device 10 is particularly advantageous since it is easy to install in and improve the communication between auxiliary transmitting/receiving units 32 located below the treetop 12 and remote areas. The transmission device 10 is easily retrieved by an airborne platform 16 and may be deployed in another area, limiting the environmental footprint.

According to another variant or in addition, the transmission system 10, and preferably included electronics, is made of a biodegradable material. Then, in case the transmission system 10 is stuck in the treetop, in particular if the first transmitting/receiving unit 38 which is under the treetop 12 is blocked into the branches, the transmission system 10 may be left in the treetop 12 and the environmental footprint is reduced.

In variant, the transmission system 10 is partially made of biodegradable material. For example, only the anchorage system is made of biodegradable material. It is left on the treetop 12. The upper mast 52, the lower mast 50, the transmission system 40 and the battery pack 64 are the only parts of the system 10 retrieved by the airborne platform 16 and/or by a ground crew.

By“biodegradable material”, it is meant that the material is able to be mineralized by soil microorganisms and or by air microorganisms. For example, a biodegradable material is a material in which more than 90% of the material is converted into carbon dioxide and water by the actions of microorganisms within two years, preferably within one year, more preferably within six months. Biodegradability can be measured for example according to standard ASTM D5988-12 whose title is“Standard test methods for determining aerobic biodegradation of plastic materials in soil”.

Advantageously, the biodegradable material is degraded in less than within 2 years, preferably within one year, more preferably within 6 months after the installation of the transmission system 10 in the treetop 12.

Preferably, the material is a biodegradable plastic. Biodegradable plastics are for example components which are derived from renewable raw materials.

Examples of biodegradable plastics are aliphatic polyesters, such as polyhydroxyalkanoates (PHA), like poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and polyhydroxyhexanoate (PHH). Other examples are polylactic acid (PLA), polybutenesuccinate (PBS), or polycaprolactone (PCL).