CA2232105C - Helicopter towed electromagnetic surveying system - Google Patents
Helicopter towed electromagnetic surveying system Download PDFInfo
- Publication number
- CA2232105C CA2232105C CA 2232105 CA2232105A CA2232105C CA 2232105 C CA2232105 C CA 2232105C CA 2232105 CA2232105 CA 2232105 CA 2232105 A CA2232105 A CA 2232105A CA 2232105 C CA2232105 C CA 2232105C
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- transmitter
- assembly
- towed
- receiver assembly
- buoyant
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/15—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat
- G01V3/17—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat operating with electromagnetic waves
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- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Remote Sensing (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Near-Field Transmission Systems (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
An airborne electromagnetic surveying system including one or several buoyant elements, particularly adapted to be towed by a helicopter. A transmitter assembly consists of a transmitting loop, a transmitter and a power supply. A receiver assembly consisting of a buoyant element carrying at least one receiving coil is towed behind the transmitter assembly whereby the buoyant element stabilizes the motion of the transmitter assembly during towing by an aircraft. This buoyant element contributes a large part to the overall performance of the system allowing for a large separation, hence use of increased radiated power as well as a stable geometry.
Description
HELICOPTER TOWED ELECTROMAGNETIC SURVEYING SYSTEM
This invention relates to an airborne electromagnetic surveying system including a buoyant element, particularly adapted to be towed by a helicopter.
Known electromagnetic surveying systems employ transmitting means carried by an aircraft and spaced sensor or receiving means, known as a "bird", towed behind the aircraft. Such a system is shown in U.S. Patent No. 4,629,990 issued December 16, 1986 to Zandee. An alternative arrangement in which spaced transmitter and sensor elements are suspended below a helicopter is shown in U.S. Patent No. 4,641,100, issued February 3, 1987 to Dzwinel. The use of a stationary dirigible as a platform for receiving signals in a seismic system is shown in U.S. Patent No. 4,236,234 issued November 25, 1980 to McDavid et al.
SUMMARY OF THE INVENTION
The electromagnetic survey system of this invention consists of a transmitter assembly adapted to be towed by a helicopter, consisting of a transmitting loop, a transmitter and a power supply; a sensor assembly consisting of a buoyant element carrying at least one receiving coil; a towing cable connecting the sensor assembly behind the transmitter assembly whereby the buoyant element dampens the motion of the transmitter assembly during towing by a helicopter.
This buoyant element contributes a large part to the overall performance of the system allowing for a large separation, hence larger radiated power and a stable geometry. Previous designs have either very low radiated power, hence little penetration, or high power and unstable geometry.
The efficiency of a airborne electromagnetic pulsed system depends upon several factors and is usually directly evaluated in terms of its penetration. The system of this invention presents major advantages:
- Optimal radiated power - Optimal transmitting and receiving coils separation - Optimal geometry for most geophysical targets In accordance with one aspect of the present invention, there is provided an airborne electromagnetic surveying system, comprising a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; a receiver assembly consisting of a towed element or drag creating element carrying at least one receiving coil; a towing cable connecting the receiver assembly behind the transmitter assembly whereby the towed element stabilizes the motion of the transmitter assembly during towing by the rotary aircraft or the airship.
In accordance with another aspect of the present invention, there is provided an airborne surveying system, comprising a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; and a receiver assembly detecting geophysical signals resulting from eddy currents induced in ground formations consisting of one or more buoyant elements carrying at least one sensor element.
This invention relates to an airborne electromagnetic surveying system including a buoyant element, particularly adapted to be towed by a helicopter.
Known electromagnetic surveying systems employ transmitting means carried by an aircraft and spaced sensor or receiving means, known as a "bird", towed behind the aircraft. Such a system is shown in U.S. Patent No. 4,629,990 issued December 16, 1986 to Zandee. An alternative arrangement in which spaced transmitter and sensor elements are suspended below a helicopter is shown in U.S. Patent No. 4,641,100, issued February 3, 1987 to Dzwinel. The use of a stationary dirigible as a platform for receiving signals in a seismic system is shown in U.S. Patent No. 4,236,234 issued November 25, 1980 to McDavid et al.
SUMMARY OF THE INVENTION
The electromagnetic survey system of this invention consists of a transmitter assembly adapted to be towed by a helicopter, consisting of a transmitting loop, a transmitter and a power supply; a sensor assembly consisting of a buoyant element carrying at least one receiving coil; a towing cable connecting the sensor assembly behind the transmitter assembly whereby the buoyant element dampens the motion of the transmitter assembly during towing by a helicopter.
This buoyant element contributes a large part to the overall performance of the system allowing for a large separation, hence larger radiated power and a stable geometry. Previous designs have either very low radiated power, hence little penetration, or high power and unstable geometry.
The efficiency of a airborne electromagnetic pulsed system depends upon several factors and is usually directly evaluated in terms of its penetration. The system of this invention presents major advantages:
- Optimal radiated power - Optimal transmitting and receiving coils separation - Optimal geometry for most geophysical targets In accordance with one aspect of the present invention, there is provided an airborne electromagnetic surveying system, comprising a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; a receiver assembly consisting of a towed element or drag creating element carrying at least one receiving coil; a towing cable connecting the receiver assembly behind the transmitter assembly whereby the towed element stabilizes the motion of the transmitter assembly during towing by the rotary aircraft or the airship.
In accordance with another aspect of the present invention, there is provided an airborne surveying system, comprising a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; and a receiver assembly detecting geophysical signals resulting from eddy currents induced in ground formations consisting of one or more buoyant elements carrying at least one sensor element.
DRAWINGS
Figure 1-A shows a side view of a transmitter assembly and towed sensor assembly;
Figure 1-B shows a plan view of the assemblies of Figures 1-A together with alternative buoyant elements;
Figure 2-A shows a side view of a survey system using several sensor -2a-assemblies being towed by a helicopter;
Figure 2-B shows a plan view of the system of Figure 2-A;
Figure 3-A shows a a side view of an arrangement similar to Figure 1, using a plurality of sensor assemblies but omitting a transmitter coil; and Figure 3-B shows a plan view of the system of Figure 3-A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1, the electromagnetic surveying system of the invention consists of a transmitter loop assembly 10 and a receiver assembly included in a drag element 21. The assemblies are towed by a helicopter 30 by means of a towing cable 31. The transmitter loop assembly 10 is adapted to be towed 150 to 200 feet beneath the helicopter and generates a pulsed electromagnetic field which affects conductors in the ground. The resulting effects are measured and analyzed through sensors mounted in the receiver assembly which is included in a drag element or buoyant vessel 21 towed behind the transmitter loop assembly.
It is connected to the helicopter by a signal carrying cable 22.
Alternatively, the signals from the receiver, known as response signals can be transmitted to the helicopter by a radio or optical link as shown in Figure 1-B. The buoyant vessel can take the form of a parachute (21 a), blimp (21 b) or balloon (21 c).
The transmitting loop 11 is a ring of large diameter (over 30 feet or 10 meters) normally flown horizontally. The loop is made of a single aluminum tube, in a preferred embodiment having a diameter of approximately 3.5" and a wall thickness of 0.1" requiring little supporting structure. The dimensions of the tube determine the performance (maximum or peak magnetic moment measured in NIA) of the transmitter assembly. If required by the electrical specifications of the transmitter, the loop can also be made of several tubes of lesser diameter arranged to form an annular bundle. These configurations offer several advantages:
- Rigid self supporting assembly (No need for supporting heavy structure) - Large area;
- Small electrical resistance, heavy current, maximum moment.
Absent restrictions concerning the power source, it can be demonstrated that the moment that can be generated with a certain weight of conducting material is at a maximum when this material is arranged to form one single turn (continuous current) and is only a function of flat weight. The dimensions of the ring (radius, tube diameter and thickness) can be varied to match a particular generator or to transmit a particular waveform.
The transmitter assembly 10 is enclosed in a ellipsoidal or cylindrical vessel to which the transmitting loop is rigidly fixed. It comprises a set of high capacity batteries, a decoupling capacitor array, a transmitter pulse-forming assembly and a bank of tuning capacitors. It generates current pulses that are circulated through the loop.
This configuration offers several advantages:
- Totally autonomous transmitting system (no power connection with the helicopter electrical system);
- The batteries can be selected for the appiication: endurance, internal resistance, weight. The energy density of sulfur-sodium cells being three to four times greater than that of equivalent NiCad cells, such batteries can allow for powerful autonomous systems (One million NIA or more with an endurance of over three hours).
In the preferred embodiment, the transmitter assembly contains two Ni-Cad batteries feeding separate pulse switches, turned on in an alternating sequence and capable of switching several thousand amperes.
The weight of the transmitter assembly and the loop depends upon the selected maximum moment and the size of the towing helicopter. It can vary from 200 to 1000 pounds or more. For a small commercial helicopter the optimal weight is approximately 600 lbs.
The transmitter can also be powered, in part or totally, by current tapped from the power source of the towing aircraft or an integrated alternator-motor assembly. Batteries and power source tapping can be combined to extend the endurance of the system, or to increase the current, the repetition rate or the width of the pulses.
The receiver assembly consists of a buoyant vessel 21 connected to the transmitter assembly 10 by a towing cable 22. This vessel contains the sensors which detect the secondary field. The sensors can be ferrite core coils or large air coils, mounted along three axes (horizontal (x), vertical (v) and transversal (z).
The vessel contains the associated electronic circuits: amplifiers, clock, DSP
(digital signal processing), digital flux feedback circuits and optical modem.
The modem transmits the data at very high rate to the processor mounted in the cabin of the helicopter. It also send triggering signals to the transmitter.
The buoyant vessel 21 is towed from the rear apex of the transmitting loop, at a distance selected to suit the application. It has a small negative buoyancy (vertical down force) and a fairly high drag (longitudinal force opposing direction of flight). The high drag serves several purposes: it maintains sufficient tension on the tow cable to stabilize the transmitting loop and the transmitter, it forms a natural damper which eliminates longitudinal and vertical jerky movements or accelerations and it gives the overall system (transmitter and receiver assemblies) a stable geometry with good separation.
The buoyant vessel 21 can be a ellipsoidal blimp (21b in Figure 1-B) inflated with helium. The blimp has a standard form and can be stabilized by fins or a parachute. The invention can also use a spherical balloon (21 C in Figure 1-B) towed in a supporting net forming an inverted cone or a specially designed parachute (21a in Figure 1-A) attached to the receiving sensors assembly as indicated in Figure 1-B. The tow cable 22 is attached to the nose of the blimp.
The receiver assembly is mounted in a specially designed chamber situated in the bottom part of the blimp. This keeps the whole assembly stable and prevents it from rolling and twisting around the tow axis.
Figures 2A and 2B show an embodiment in which several detectors are used simultaneously in buoyant vessels 21 a, 21 b and 21 c with lateral or vertical spacing using a spreader as known for use in sonar or seismic arrays and shown in Figure 3-B.
A downrigger technique can be used with any vessel causing drag such as a blimp or zeppelin using a dead weight 41 (ball or heavy object) suspended underneath the helicopter as tow point as shown in Figures 3-A and 3-B. This downrigger can be used for other applications such as magnetometery or gravimetry not requiring a transmitter element. Drag inducing vessels of other shapes such as blimp, zeppelin, drag-chute or windsock configuration can be used.
The towed downrigger configuration can be used to tow several laterally or vertically spaced buoyant elements 21a, 21b and 21c as shown in Figure 3-B, containing detectors, using a spreader 42, as used in sonar or seismic arrays.
The spreaders 42 are designed to steer the buoyant vessels 21 away from the axis of towing cable 22 until they stabilize themselves on lines left or right, below or above the flight path. Spatial separation (vertical, lateral and longitudinal) can be obtain by varying the ballast or volume, the length of the tow ropes 23 or the angle of attack of the spreaders.
This arrangement provides improved resolution and a substantial saving in flight time, since the system can cover two or three lines in one path and measure transversal, longitudinal or vertical gradients. It can be used with different type of sensors such as: magnetometers, VLF sensors, laser altimeters, remote sensing devices including spectrometers and sniffers.
Figure 1-A shows a side view of a transmitter assembly and towed sensor assembly;
Figure 1-B shows a plan view of the assemblies of Figures 1-A together with alternative buoyant elements;
Figure 2-A shows a side view of a survey system using several sensor -2a-assemblies being towed by a helicopter;
Figure 2-B shows a plan view of the system of Figure 2-A;
Figure 3-A shows a a side view of an arrangement similar to Figure 1, using a plurality of sensor assemblies but omitting a transmitter coil; and Figure 3-B shows a plan view of the system of Figure 3-A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1, the electromagnetic surveying system of the invention consists of a transmitter loop assembly 10 and a receiver assembly included in a drag element 21. The assemblies are towed by a helicopter 30 by means of a towing cable 31. The transmitter loop assembly 10 is adapted to be towed 150 to 200 feet beneath the helicopter and generates a pulsed electromagnetic field which affects conductors in the ground. The resulting effects are measured and analyzed through sensors mounted in the receiver assembly which is included in a drag element or buoyant vessel 21 towed behind the transmitter loop assembly.
It is connected to the helicopter by a signal carrying cable 22.
Alternatively, the signals from the receiver, known as response signals can be transmitted to the helicopter by a radio or optical link as shown in Figure 1-B. The buoyant vessel can take the form of a parachute (21 a), blimp (21 b) or balloon (21 c).
The transmitting loop 11 is a ring of large diameter (over 30 feet or 10 meters) normally flown horizontally. The loop is made of a single aluminum tube, in a preferred embodiment having a diameter of approximately 3.5" and a wall thickness of 0.1" requiring little supporting structure. The dimensions of the tube determine the performance (maximum or peak magnetic moment measured in NIA) of the transmitter assembly. If required by the electrical specifications of the transmitter, the loop can also be made of several tubes of lesser diameter arranged to form an annular bundle. These configurations offer several advantages:
- Rigid self supporting assembly (No need for supporting heavy structure) - Large area;
- Small electrical resistance, heavy current, maximum moment.
Absent restrictions concerning the power source, it can be demonstrated that the moment that can be generated with a certain weight of conducting material is at a maximum when this material is arranged to form one single turn (continuous current) and is only a function of flat weight. The dimensions of the ring (radius, tube diameter and thickness) can be varied to match a particular generator or to transmit a particular waveform.
The transmitter assembly 10 is enclosed in a ellipsoidal or cylindrical vessel to which the transmitting loop is rigidly fixed. It comprises a set of high capacity batteries, a decoupling capacitor array, a transmitter pulse-forming assembly and a bank of tuning capacitors. It generates current pulses that are circulated through the loop.
This configuration offers several advantages:
- Totally autonomous transmitting system (no power connection with the helicopter electrical system);
- The batteries can be selected for the appiication: endurance, internal resistance, weight. The energy density of sulfur-sodium cells being three to four times greater than that of equivalent NiCad cells, such batteries can allow for powerful autonomous systems (One million NIA or more with an endurance of over three hours).
In the preferred embodiment, the transmitter assembly contains two Ni-Cad batteries feeding separate pulse switches, turned on in an alternating sequence and capable of switching several thousand amperes.
The weight of the transmitter assembly and the loop depends upon the selected maximum moment and the size of the towing helicopter. It can vary from 200 to 1000 pounds or more. For a small commercial helicopter the optimal weight is approximately 600 lbs.
The transmitter can also be powered, in part or totally, by current tapped from the power source of the towing aircraft or an integrated alternator-motor assembly. Batteries and power source tapping can be combined to extend the endurance of the system, or to increase the current, the repetition rate or the width of the pulses.
The receiver assembly consists of a buoyant vessel 21 connected to the transmitter assembly 10 by a towing cable 22. This vessel contains the sensors which detect the secondary field. The sensors can be ferrite core coils or large air coils, mounted along three axes (horizontal (x), vertical (v) and transversal (z).
The vessel contains the associated electronic circuits: amplifiers, clock, DSP
(digital signal processing), digital flux feedback circuits and optical modem.
The modem transmits the data at very high rate to the processor mounted in the cabin of the helicopter. It also send triggering signals to the transmitter.
The buoyant vessel 21 is towed from the rear apex of the transmitting loop, at a distance selected to suit the application. It has a small negative buoyancy (vertical down force) and a fairly high drag (longitudinal force opposing direction of flight). The high drag serves several purposes: it maintains sufficient tension on the tow cable to stabilize the transmitting loop and the transmitter, it forms a natural damper which eliminates longitudinal and vertical jerky movements or accelerations and it gives the overall system (transmitter and receiver assemblies) a stable geometry with good separation.
The buoyant vessel 21 can be a ellipsoidal blimp (21b in Figure 1-B) inflated with helium. The blimp has a standard form and can be stabilized by fins or a parachute. The invention can also use a spherical balloon (21 C in Figure 1-B) towed in a supporting net forming an inverted cone or a specially designed parachute (21a in Figure 1-A) attached to the receiving sensors assembly as indicated in Figure 1-B. The tow cable 22 is attached to the nose of the blimp.
The receiver assembly is mounted in a specially designed chamber situated in the bottom part of the blimp. This keeps the whole assembly stable and prevents it from rolling and twisting around the tow axis.
Figures 2A and 2B show an embodiment in which several detectors are used simultaneously in buoyant vessels 21 a, 21 b and 21 c with lateral or vertical spacing using a spreader as known for use in sonar or seismic arrays and shown in Figure 3-B.
A downrigger technique can be used with any vessel causing drag such as a blimp or zeppelin using a dead weight 41 (ball or heavy object) suspended underneath the helicopter as tow point as shown in Figures 3-A and 3-B. This downrigger can be used for other applications such as magnetometery or gravimetry not requiring a transmitter element. Drag inducing vessels of other shapes such as blimp, zeppelin, drag-chute or windsock configuration can be used.
The towed downrigger configuration can be used to tow several laterally or vertically spaced buoyant elements 21a, 21b and 21c as shown in Figure 3-B, containing detectors, using a spreader 42, as used in sonar or seismic arrays.
The spreaders 42 are designed to steer the buoyant vessels 21 away from the axis of towing cable 22 until they stabilize themselves on lines left or right, below or above the flight path. Spatial separation (vertical, lateral and longitudinal) can be obtain by varying the ballast or volume, the length of the tow ropes 23 or the angle of attack of the spreaders.
This arrangement provides improved resolution and a substantial saving in flight time, since the system can cover two or three lines in one path and measure transversal, longitudinal or vertical gradients. It can be used with different type of sensors such as: magnetometers, VLF sensors, laser altimeters, remote sensing devices including spectrometers and sniffers.
Claims (16)
1. An airborne electromagnetic surveying system, comprising:
a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply;
a receiver assembly consisting of a towed element or drag creating element carrying at least one receiving coil;
a towing cable connecting the receiver assembly behind the transmitter assembly whereby the towed element stabilizes the motion of the transmitter assembly during towing by the rotary aircraft or the airship.
a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply;
a receiver assembly consisting of a towed element or drag creating element carrying at least one receiving coil;
a towing cable connecting the receiver assembly behind the transmitter assembly whereby the towed element stabilizes the motion of the transmitter assembly during towing by the rotary aircraft or the airship.
2. The system as in claim 1, whereby the towed element introduces significant drag.
3. The system as in claim 1 or 2, wherein the towed element consists of a buoyant helium inflated blimp or balloon held in a supporting net connected to the towing cable.
4. The system as in claim 1, 2 or 3, whereby the towing cable is connected to the rear of the transmitter assembly.
5. The system as in any one of claims 1 to 4, wherein the transmitting loop is a single rigid turn made of a self-supporting tubing.
6. The system as in claim 5, wherein the loop is of ellipsoidal or circular configuration.
7. The system as in any one of claims 1 to 6, further including a signal carrying cable extending from the receiver assembly to the towing aircraft to permit monitoring of signals from the receiving coil.
8. The system as in any one of claims 1 to 6 in which signals from the receiving coil are transmitted to the aircraft via a radio link or an optical link.
9. The system as in any one of claims 1 to 8, wherein the receiver assembly consists of a plurality of buoyant elements each carrying at least one receiver coil, adapted to be vertically or horizontally separated from one another in operation.
10. An airborne surveying system, comprising:
a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; and a receiver assembly detecting geophysical signals resulting from eddy currents induced in ground formations consisting of one or more buoyant elements carrying at least one sensor element.
a transmitter assembly, adapted to be towed by a rotary aircraft or by an airship, consisting of a tubular transmitting loop of single or multiple turns, a transmitter and a power supply; and a receiver assembly detecting geophysical signals resulting from eddy currents induced in ground formations consisting of one or more buoyant elements carrying at least one sensor element.
11. The system as in claim 10 further comprising a downrigger weight and a towing cable connecting the receiver assembly to the downrigger weight and whereby the one or more buoyant elements introduces significant drag during the towing operation.
12. The system as in claim 10 or 11, wherein the one or more buoyant elements consist of a helium inflated balloon or a blimp.
13. The system as in claim 10, 11 or 12, further comprising a signal carrying cable adapted to extend from the receiver assembly to the rotary aircraft or airship to permit monitoring of said geophysical signals from the sensor element.
14. The system as in claim 10, wherein the receiver assembly consists of a plurality of buoyant elements each carrying at least one sensor, adapted to be vertically or horizontally spaced from one another in operation.
15. The system as in any one of claims 1, 2 or 4 to 9, wherein the towed element consists of a light, egg-shaped vessel and a drag parachute.
16. The system as in any one of claims 1 to 15, wherein the transmitting loop is a bundle of several tubes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2232105 CA2232105C (en) | 1998-03-13 | 1998-03-13 | Helicopter towed electromagnetic surveying system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2232105 CA2232105C (en) | 1998-03-13 | 1998-03-13 | Helicopter towed electromagnetic surveying system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2232105A1 CA2232105A1 (en) | 1999-09-13 |
| CA2232105C true CA2232105C (en) | 2008-08-26 |
Family
ID=29409451
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2232105 Expired - Fee Related CA2232105C (en) | 1998-03-13 | 1998-03-13 | Helicopter towed electromagnetic surveying system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2232105C (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101067660A (en) | 2002-11-20 | 2007-11-07 | 爱德华·贝弗莉·莫里森 | Airborne electromagnetic time domain system, computer product and method |
| CA2564183C (en) * | 2004-04-28 | 2013-11-26 | Anglo Operations Limited | Helicopter electromagnetic prospecting system |
| US6845936B1 (en) * | 2004-07-21 | 2005-01-25 | Geophysique G.P.R. International Inc. | Stable heli-borne vector platform for performing geophysical measurements |
| RU2734661C1 (en) * | 2020-03-05 | 2020-10-21 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Кубанский государственный аграрный университет имени И.Т. Трубилина" | Complex of unmanned aerial vehicles based on aerostatic aircraft |
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1998
- 1998-03-13 CA CA 2232105 patent/CA2232105C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2232105A1 (en) | 1999-09-13 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20130313 |