CA2079743C - Method and apparatus for determining the position of an aerial camera at the time of shutter release - Google Patents
Method and apparatus for determining the position of an aerial camera at the time of shutter releaseInfo
- Publication number
- CA2079743C CA2079743C CA 2079743 CA2079743A CA2079743C CA 2079743 C CA2079743 C CA 2079743C CA 2079743 CA2079743 CA 2079743 CA 2079743 A CA2079743 A CA 2079743A CA 2079743 C CA2079743 C CA 2079743C
- Authority
- CA
- Canada
- Prior art keywords
- photodetector
- camera
- receiver
- gps
- shutter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for obtaining data from which to determine the location of an aerial camera at the time of shutter opening, the apparatus comprising a GPS continuously recording data received from a GPS satellite, a photodetector for mounting inside an aerial camera for detecting the opening of the shutter of the camera; and means connecting the photodetector to receiver for carrying a time marking signal from the detector to the receiver.
An apparatus for obtaining data from which to determine the location of an aerial camera at the time of shutter opening, the apparatus comprising a GPS continuously recording data received from a GPS satellite, a photodetector for mounting inside an aerial camera for detecting the opening of the shutter of the camera; and means connecting the photodetector to receiver for carrying a time marking signal from the detector to the receiver.
Description
2~)`797L13 TITLE OF T~IB INVE~NTION ~ ~ -~IET~IOD A~D APPARAq~U~3 FOR DETERPIINING T~E POSITIO~ :
0~1? AN AERIAI~ CANBRA AT T}~E: TI~ OF ~UTTER REI.EA~E
,~ ~: ., PIELD OF THB INVBNTION ~ ~ ~
";~
~his invention relates to aerial photography and to a method and apparatus for determining with accuracy the position of an aerial camera at the time of shutter release.
BACl~GROUND OF THE INVBNTION
The mapping process is one which has concerned civilizations from ancient times. The fundamental value of a map even in the crudest form must have been recognized very early by prehistoric nomadic man. As civilizations developed, the need for more accurate and more sophisticated maps became readily apparent.
The need often arose out of military or trading expeditions.
Mapping was, during its infancy, laborious and time consuming in the extreme. The importance of mapping, however, dictated that considerable effort would be put into the improvément of techniques.
The arrival of aerial mapping methods, centering on aerial photography, revolutionized mapping and allowed for more complete and accurate maps to be prepared more quickly.
- 2 - 2 or79 ~ ~5 The process was again substantially enhanced by the arrival of electronic data processing and technology.
All of these advances left the ground control and field work segment of the process as a major cost component. This is because ground control is necessary to establish the position of the aerial camera when a given aerial photograph was taken.
Against this background, a method and apparatus have now been developed by which the position of the camera can be established through the use of the Global Positioning System (GPS) satellites, so that *he ground component of the survey can be very substantially reduced.
PRIOR ART
Applicant is not aware of any prior documents which pertain to the invention.
~ '.
BRI~F 8UMMARY OF THE INVENTION
A system has now been devised whereby a photo detector placed inside an aerial camera body is used to determine the moment at which the camera shutter is released. A signal from the photo detector is fed to a GPS receiver and the precise time of the signal's arrival at the receiver is recorded as an event without interrupting the reception of a continuous stream of signals from the GPS satellites. The nature of GPS positioning assures an accurate knowledge of the exact time. The GPS data, .,.. : . .. .. . , . :-.,, : . . ~., . -- 3 - 2~7~7~ ~
with the times of the photo detector pulses, is stored and processed later to provide the altitude, latitude and longitude of the perspective center of the camera.
Thus, the invention provides an apparatus for obtaining data from which to determine the location of an aerial camera at the time of shutter opening, the apparatus comprising a GPS
receiver for continuously recording data received from a GPS
satellite, a photodetector for mounting inside an aerial camera for detecting the opening of the shutter of the camera, and means for connecting the photodetector to the receiver for carrying a time marking signal from the detector to the receiver.
In a further embodiment there is provided a method for determining the location of an aerial camera at the moment when the camera has taken a photograph, the method comprising mounting a photodetector within the camera for detecting the admission of ;~ light through the shutter of the camera, continuously monitoring and recording signals from a GPS satellite using a GPS satellite receiver, transmitting a time marking signal from the photodetector to the GPS receiver and calculating the camera position from the time marked GPS data.
'',,.~.,~ ~ ";, BRIEF DE~CRIPq!ION OF THE DRAWING ~; .. `.
These and other objects and advantages of the invention will become apparent upon reading the following detailed description and upon referring to the drawings in which~
'' '~ ' ` "','~:'.'""' .. ::
0~1? AN AERIAI~ CANBRA AT T}~E: TI~ OF ~UTTER REI.EA~E
,~ ~: ., PIELD OF THB INVBNTION ~ ~ ~
";~
~his invention relates to aerial photography and to a method and apparatus for determining with accuracy the position of an aerial camera at the time of shutter release.
BACl~GROUND OF THE INVBNTION
The mapping process is one which has concerned civilizations from ancient times. The fundamental value of a map even in the crudest form must have been recognized very early by prehistoric nomadic man. As civilizations developed, the need for more accurate and more sophisticated maps became readily apparent.
The need often arose out of military or trading expeditions.
Mapping was, during its infancy, laborious and time consuming in the extreme. The importance of mapping, however, dictated that considerable effort would be put into the improvément of techniques.
The arrival of aerial mapping methods, centering on aerial photography, revolutionized mapping and allowed for more complete and accurate maps to be prepared more quickly.
- 2 - 2 or79 ~ ~5 The process was again substantially enhanced by the arrival of electronic data processing and technology.
All of these advances left the ground control and field work segment of the process as a major cost component. This is because ground control is necessary to establish the position of the aerial camera when a given aerial photograph was taken.
Against this background, a method and apparatus have now been developed by which the position of the camera can be established through the use of the Global Positioning System (GPS) satellites, so that *he ground component of the survey can be very substantially reduced.
PRIOR ART
Applicant is not aware of any prior documents which pertain to the invention.
~ '.
BRI~F 8UMMARY OF THE INVENTION
A system has now been devised whereby a photo detector placed inside an aerial camera body is used to determine the moment at which the camera shutter is released. A signal from the photo detector is fed to a GPS receiver and the precise time of the signal's arrival at the receiver is recorded as an event without interrupting the reception of a continuous stream of signals from the GPS satellites. The nature of GPS positioning assures an accurate knowledge of the exact time. The GPS data, .,.. : . .. .. . , . :-.,, : . . ~., . -- 3 - 2~7~7~ ~
with the times of the photo detector pulses, is stored and processed later to provide the altitude, latitude and longitude of the perspective center of the camera.
Thus, the invention provides an apparatus for obtaining data from which to determine the location of an aerial camera at the time of shutter opening, the apparatus comprising a GPS
receiver for continuously recording data received from a GPS
satellite, a photodetector for mounting inside an aerial camera for detecting the opening of the shutter of the camera, and means for connecting the photodetector to the receiver for carrying a time marking signal from the detector to the receiver.
In a further embodiment there is provided a method for determining the location of an aerial camera at the moment when the camera has taken a photograph, the method comprising mounting a photodetector within the camera for detecting the admission of ;~ light through the shutter of the camera, continuously monitoring and recording signals from a GPS satellite using a GPS satellite receiver, transmitting a time marking signal from the photodetector to the GPS receiver and calculating the camera position from the time marked GPS data.
'',,.~.,~ ~ ";, BRIEF DE~CRIPq!ION OF THE DRAWING ~; .. `.
These and other objects and advantages of the invention will become apparent upon reading the following detailed description and upon referring to the drawings in which~
'' '~ ' ` "','~:'.'""' .. ::
- 4 - :
FIGURE 1 is a schematic drawing illustrating the components of an apparatus according to the invention;
FIGURE 2 is a schematic diagram illustrating a preferred location of a photodetector in an aerial camera for use in the present invention;
FIGURE 3 is a circuit diagram from a power supply for use with the photodetector of the invention;
FIGURE 4 is a wiring diagram illustrating a photodetector sensor and amplifier for use in the invention; and FIGURES 5A and 5B illustrate two halves of a wiring diagram for a shutter release detector counter for use in the invention; and FIGURE 6 indicates the positioning of combined FIGURE 5A
and 5B.
While the invention will be described in conjunction with illustrated embodiments, it will be understood that it is not : intended to limit the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications ;
and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODINENTS
,:
In its simplest form, the apparatus 20 comprises a -photodetector 12 for mounting inside an aerial camera 14, a GPS .
receiver 16 and connecting means 18 for carrying a signal from photodetector 12 to GPS receiver 16. - .
,, ,.~. ,,~................................................................ :
-~` 207~7~3 Photodetector 12 is preferably in conventional form comprising a small disc mounted on cylinder 13. ;~ -The connecting means 18 in the preferred configuration comprises an amplifier 20 for amplifying the signal from the photodetector to a level sufficient to trigger a comparator 22.
The comparator output is a pulse preferably delivered via a BNC
cable 24 to the GPS receiver 16.
In the preferred case, a pulse counter 26 is interposed to provide a cumulative total for the number of shutter openings which have occurred.
A GPS antenna 28 is a part of, although mounted remote ~-from, the receiver 16. ~;
The photodetector is chosen to meet several criteria.
First, since the aircraft may be travelling at several hundred miles per hour, the response time must be very fast. For example, an aircraft travelling at 200 miles per hour is travelling at -~
approximately 0.01 centimeters per microsecond. Thus, the response --`
time of 10 microseconds in the detector would lead to a positional error of about 0.1 centimeters. The preferred photodetector will ... ..
have a response time less than 10 microseconds, although this requirement may be adjusted to suit a particular situation. -Furthermore, the light intensity which will be seen by the photodetector will vary, and the detector must be capable of ' ~''` ' 'r' providing an adequate response to both bright or dark spots in the image.
In addition to these operational parameters, the photodetector should be mounted in an area of unfocused or diffused , - 6 - 2 07 q7 43 light, in order that it does not see specific dark parts of an otherwise bright image.
As well, the detector is preferably mounted perpendicular to the image in the lens, thus with full face to the light column.
Otherwise, the amount of light incident on the detector will be decreased, thus decreasing effective sensitivity.
This positioning is illustrated in Figure 2. The light beam from the lens will be dispersed as a flairing beam of generally circular cross-section (the cross-section conforming to that of the lens). The photodetector 12 and cylinder 13 are preferably mounted in the corner 15 of the lens frame 30, so that the photodetector 12 is in the corner gap between the circular cross-section beam and the square configuration lens frame 30.
Photodetector 12 is thus in an area of diffused light and is substantially face-on to that part of the beam adjacent the lens.
PIN diodes are the preferred form of photodetector. Such diodes are fast and have low dark currents. Thus, lower quantities of light can be resolved. A typical PIN detector such as a Siemens BPX61 or RCA C30808, can detect power densities down to about 8 microwatts per square centimeter.
It is notable that there may be 300,000 times as much light at the camera input than actually reaches the photodetector.
Since the output current of the detector for the 8 microwatt per square centimeter minimum power density will be in the sub- 0.3 microamperes range, it is necessary to amplify the low output current to a level which will trigger a comparator. The amplification may be accomplished in various ways, as can be ~A
r~$"m~
~ 7 ~ 20797~3 :, :.
devised by a person skilled in the art. The preferred format utilizes an NE5212 transimpedence amplifier in combination with an MC1590G amplifier. This combination will amplify the low 0.3 microamp current to about 20 mV which is sufficient to trigger the comparator.
A preferred comparator is the LM311, which has a response time of 200 nsec.
The counter 26 would typically comprise an MC14553 three digit counter, a 74LS247 decoder driver and three MAN4610A
displays. A reset switch is preferably provided to zero the accumulated count.
In order to reduce the possibility of false counts brought about, for example, by the photodetector detecting changing light conditions during the period when the shutter is open, a blanking pulse is utilized to mask the system for a short period.
Thus, when the photodetector first detects light and the comparator consequently reacts, a blanking pulse of, say, 0.5 second duration is generated to mask the system for that period to prevent false . .:.: .
counts. .-;
The apparatus preferably includes audible or visible warning means during shutter opening. This warning means is ```
preferably a flashing light source.
; ,- ~ : .
The warning means and a display of the cumulative total i -of the pulse count may conveniently be provided by the three-digit ;`--:--' .
LED display LD1, LD2 and LD3 illustrated in the counter, Figure 5B. ~ ;
The three digits display the count and the three decimal points ~ ~
, . . .
. " , "
';' ~''''' ' :, ... .
shown as DP in LD1, LD2 and LD3 are wired to provide the flashing light warning means.
In conventional manner an amplifier and audible device may be wired into the DP circuitry to provide an audible alarm, if desired.
Power for the apparatus is preferably provided from the aircraft 28 volt power supply. For the preferred components the power supply requirement is 5 volts at 150 mA. Since the aircraft power supply is not regulated, transient protection is required for the apparatus regulator. Transient protection is preferably obtained by utilizing transorbs. A suitable regulator is an LM7805CT five volt regulator with a heat sink to dissipate heat from the regulator and this is preferably obtained by bolting the regulator to an apparatus casing.
15As illustrated in FIGURE 2, the actual positioning of the photodetector 12 is preferably in a corner of lens frame 30 so as ;~ to minimize the appearance on the photo. Photodetector 12 is held in place in the lens frame 30, preferably by silicone or rubber cement. For maximum efficiency, the detector is perpendicular to the image in the camera; as with the detector fully facing the light column. The detector and associated electronics will I ~!i. generally be able to be fitted into any aerial camera. For this reasonj that part of the system is preferably limited to a tube of one centimeter in diameter by three centimeters in length, which will contain the photodetector, the amplifier and the comparator.
While not a part of the inventive system per se, the GPS
antenna 28 is preferably mounted on the aircraft directly over the . .
center of the camera plate. This eliminates from the computation most transformation problems brought about by any different position of the antenna from the plate.
To utilize the apparatus, two initial reference points are first chosen, the locations of which are precisely known. One of these points is occupied by a stationery receiver (base) while the other is occupied by the aircraft, positioned so that the antenna on the aircraft is directly over the known point. After an initialization period of about one minute, the aircraft may move.
This method is normally described as "kinematic". The aircraft takes off and the required aerial photographs are taken with the apparatus of the invention feeding pulses to be time-stamped by the receiver into the receiver each time the camera shutter is opened.
When the photography run has been completed, the aircraft returns to the reference point to check the positioning, the receivers having been operating continuously through this operation.
The recorded data is then processed and interpolated to yield the position of the center of the camera plate for each photograph taken.
Thus it is apparent that there has been provided in accordance with the invention method and apparatus for determining the position of an aerial camera at the time of shutter release that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description.
, ~ ':`,,, 207q743:
Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the invention.
-~ .
_" ~:
~' i.' ~' .
FIGURE 1 is a schematic drawing illustrating the components of an apparatus according to the invention;
FIGURE 2 is a schematic diagram illustrating a preferred location of a photodetector in an aerial camera for use in the present invention;
FIGURE 3 is a circuit diagram from a power supply for use with the photodetector of the invention;
FIGURE 4 is a wiring diagram illustrating a photodetector sensor and amplifier for use in the invention; and FIGURES 5A and 5B illustrate two halves of a wiring diagram for a shutter release detector counter for use in the invention; and FIGURE 6 indicates the positioning of combined FIGURE 5A
and 5B.
While the invention will be described in conjunction with illustrated embodiments, it will be understood that it is not : intended to limit the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications ;
and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODINENTS
,:
In its simplest form, the apparatus 20 comprises a -photodetector 12 for mounting inside an aerial camera 14, a GPS .
receiver 16 and connecting means 18 for carrying a signal from photodetector 12 to GPS receiver 16. - .
,, ,.~. ,,~................................................................ :
-~` 207~7~3 Photodetector 12 is preferably in conventional form comprising a small disc mounted on cylinder 13. ;~ -The connecting means 18 in the preferred configuration comprises an amplifier 20 for amplifying the signal from the photodetector to a level sufficient to trigger a comparator 22.
The comparator output is a pulse preferably delivered via a BNC
cable 24 to the GPS receiver 16.
In the preferred case, a pulse counter 26 is interposed to provide a cumulative total for the number of shutter openings which have occurred.
A GPS antenna 28 is a part of, although mounted remote ~-from, the receiver 16. ~;
The photodetector is chosen to meet several criteria.
First, since the aircraft may be travelling at several hundred miles per hour, the response time must be very fast. For example, an aircraft travelling at 200 miles per hour is travelling at -~
approximately 0.01 centimeters per microsecond. Thus, the response --`
time of 10 microseconds in the detector would lead to a positional error of about 0.1 centimeters. The preferred photodetector will ... ..
have a response time less than 10 microseconds, although this requirement may be adjusted to suit a particular situation. -Furthermore, the light intensity which will be seen by the photodetector will vary, and the detector must be capable of ' ~''` ' 'r' providing an adequate response to both bright or dark spots in the image.
In addition to these operational parameters, the photodetector should be mounted in an area of unfocused or diffused , - 6 - 2 07 q7 43 light, in order that it does not see specific dark parts of an otherwise bright image.
As well, the detector is preferably mounted perpendicular to the image in the lens, thus with full face to the light column.
Otherwise, the amount of light incident on the detector will be decreased, thus decreasing effective sensitivity.
This positioning is illustrated in Figure 2. The light beam from the lens will be dispersed as a flairing beam of generally circular cross-section (the cross-section conforming to that of the lens). The photodetector 12 and cylinder 13 are preferably mounted in the corner 15 of the lens frame 30, so that the photodetector 12 is in the corner gap between the circular cross-section beam and the square configuration lens frame 30.
Photodetector 12 is thus in an area of diffused light and is substantially face-on to that part of the beam adjacent the lens.
PIN diodes are the preferred form of photodetector. Such diodes are fast and have low dark currents. Thus, lower quantities of light can be resolved. A typical PIN detector such as a Siemens BPX61 or RCA C30808, can detect power densities down to about 8 microwatts per square centimeter.
It is notable that there may be 300,000 times as much light at the camera input than actually reaches the photodetector.
Since the output current of the detector for the 8 microwatt per square centimeter minimum power density will be in the sub- 0.3 microamperes range, it is necessary to amplify the low output current to a level which will trigger a comparator. The amplification may be accomplished in various ways, as can be ~A
r~$"m~
~ 7 ~ 20797~3 :, :.
devised by a person skilled in the art. The preferred format utilizes an NE5212 transimpedence amplifier in combination with an MC1590G amplifier. This combination will amplify the low 0.3 microamp current to about 20 mV which is sufficient to trigger the comparator.
A preferred comparator is the LM311, which has a response time of 200 nsec.
The counter 26 would typically comprise an MC14553 three digit counter, a 74LS247 decoder driver and three MAN4610A
displays. A reset switch is preferably provided to zero the accumulated count.
In order to reduce the possibility of false counts brought about, for example, by the photodetector detecting changing light conditions during the period when the shutter is open, a blanking pulse is utilized to mask the system for a short period.
Thus, when the photodetector first detects light and the comparator consequently reacts, a blanking pulse of, say, 0.5 second duration is generated to mask the system for that period to prevent false . .:.: .
counts. .-;
The apparatus preferably includes audible or visible warning means during shutter opening. This warning means is ```
preferably a flashing light source.
; ,- ~ : .
The warning means and a display of the cumulative total i -of the pulse count may conveniently be provided by the three-digit ;`--:--' .
LED display LD1, LD2 and LD3 illustrated in the counter, Figure 5B. ~ ;
The three digits display the count and the three decimal points ~ ~
, . . .
. " , "
';' ~''''' ' :, ... .
shown as DP in LD1, LD2 and LD3 are wired to provide the flashing light warning means.
In conventional manner an amplifier and audible device may be wired into the DP circuitry to provide an audible alarm, if desired.
Power for the apparatus is preferably provided from the aircraft 28 volt power supply. For the preferred components the power supply requirement is 5 volts at 150 mA. Since the aircraft power supply is not regulated, transient protection is required for the apparatus regulator. Transient protection is preferably obtained by utilizing transorbs. A suitable regulator is an LM7805CT five volt regulator with a heat sink to dissipate heat from the regulator and this is preferably obtained by bolting the regulator to an apparatus casing.
15As illustrated in FIGURE 2, the actual positioning of the photodetector 12 is preferably in a corner of lens frame 30 so as ;~ to minimize the appearance on the photo. Photodetector 12 is held in place in the lens frame 30, preferably by silicone or rubber cement. For maximum efficiency, the detector is perpendicular to the image in the camera; as with the detector fully facing the light column. The detector and associated electronics will I ~!i. generally be able to be fitted into any aerial camera. For this reasonj that part of the system is preferably limited to a tube of one centimeter in diameter by three centimeters in length, which will contain the photodetector, the amplifier and the comparator.
While not a part of the inventive system per se, the GPS
antenna 28 is preferably mounted on the aircraft directly over the . .
center of the camera plate. This eliminates from the computation most transformation problems brought about by any different position of the antenna from the plate.
To utilize the apparatus, two initial reference points are first chosen, the locations of which are precisely known. One of these points is occupied by a stationery receiver (base) while the other is occupied by the aircraft, positioned so that the antenna on the aircraft is directly over the known point. After an initialization period of about one minute, the aircraft may move.
This method is normally described as "kinematic". The aircraft takes off and the required aerial photographs are taken with the apparatus of the invention feeding pulses to be time-stamped by the receiver into the receiver each time the camera shutter is opened.
When the photography run has been completed, the aircraft returns to the reference point to check the positioning, the receivers having been operating continuously through this operation.
The recorded data is then processed and interpolated to yield the position of the center of the camera plate for each photograph taken.
Thus it is apparent that there has been provided in accordance with the invention method and apparatus for determining the position of an aerial camera at the time of shutter release that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description.
, ~ ':`,,, 207q743:
Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the invention.
-~ .
_" ~:
~' i.' ~' .
Claims (16)
1. An apparatus for obtaining data from which to determine the location of an aerial camera at the time of shutter opening, said apparatus comprising:
a GPS receiver continuously recording data received from GPS satellites;
a photodetector mounted inside an aerial camera for detecting the opening of the shutter of said camera; and means connecting said photodetector to said receiver for carrying a time marking signal from said photodetector to said receiver and for interposing said time marking signal directly on said GPS data in said receiver.
a GPS receiver continuously recording data received from GPS satellites;
a photodetector mounted inside an aerial camera for detecting the opening of the shutter of said camera; and means connecting said photodetector to said receiver for carrying a time marking signal from said photodetector to said receiver and for interposing said time marking signal directly on said GPS data in said receiver.
2. The apparatus of claim 1 wherein said means connecting include an amplifier for amplifying said signal from said detector.
3. The apparatus of claim 2 wherein said means connecting includes a comparator for receiving a signal from said amplifier, converting said signal to a time marking pulse compatible with said GPS receiver and forwarding said time marking pulse to said receiver.
4. The apparatus of claim 3 wherein said means connecting includes a BNC cable connecting the comparator to the GPS
receiver.
receiver.
5. The apparatus of claim 4 comprising, in addition, audible or visible warning means during said shutter opening.
6. The apparatus of claim 5 wherein said warning means comprises a flashing light source.
7. The apparatus of claim 4 comprising, in addition, a shutter release counter for recording and displaying a cumulative total of shutter openings.
8. The apparatus of claim 1 wherein the photodetector is a PIN diode.
9. The apparatus of claim 8 wherein said photodetector has a response time not greater than 10 microsecond (µsec).
10. The apparatus of claim 8 wherein said photodetector has a sensitivity of about 8 microwatts/cm2 (8µwatt/cm2).
11. The apparatus of claim 1 wherein said photodetector is oriented perpendicular to an image striking said camera.
12. A method for determining the location of an aerial camera at the moment when said camera has taken a photograph, said method comprising:
mounting a photodetector within said camera for detecting the admission of light through the shutter of said camera;
continuously monitoring and recording signals from GPS
satellites using a GPS satellite receiver;
transmitting a time marking signal from said photodetector to said GPS receiver and interposing in said receiver said time marking signal on said signals from GPS
satellites; and calculating the camera position from the time marked GPS
data.
mounting a photodetector within said camera for detecting the admission of light through the shutter of said camera;
continuously monitoring and recording signals from GPS
satellites using a GPS satellite receiver;
transmitting a time marking signal from said photodetector to said GPS receiver and interposing in said receiver said time marking signal on said signals from GPS
satellites; and calculating the camera position from the time marked GPS
data.
13. The method of claim 12 comprising, in addition, amplifying and conditioning said time marking signal to a time marking pulse acceptable to said receiver.
14. The method of claim 12 comprising, in addition, orienting said photodetector perpendicular to an image received in said camera.
15. The method of claim 12 comprising, in addition, locating said photodetector in an area of said camera which will receive unfocused light.
16. The method of claim 12 comprising, in addition, recording a cumulative total of shutter openings of said camera.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76972591A | 1991-10-02 | 1991-10-02 | |
| US07/769,725 | 1991-10-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2079743A1 CA2079743A1 (en) | 1993-04-03 |
| CA2079743C true CA2079743C (en) | 1994-05-31 |
Family
ID=25086347
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2079743 Expired - Fee Related CA2079743C (en) | 1991-10-02 | 1992-10-02 | Method and apparatus for determining the position of an aerial camera at the time of shutter release |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2079743C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103292790A (en) * | 2012-03-01 | 2013-09-11 | 贵州帝三数字技术有限公司 | Intelligent aerial photography shutter trigger |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4422411A1 (en) * | 1993-07-13 | 1995-01-19 | Deutsche Aerospace | Process for monitoring areas on the ground and arrangement for carrying out the process |
| EP0650125A1 (en) * | 1993-10-20 | 1995-04-26 | Nippon Lsi Card Co., Ltd. | Handy computer with built-in digital camera and spot state recording method using the same |
-
1992
- 1992-10-02 CA CA 2079743 patent/CA2079743C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103292790A (en) * | 2012-03-01 | 2013-09-11 | 贵州帝三数字技术有限公司 | Intelligent aerial photography shutter trigger |
| CN103292790B (en) * | 2012-03-01 | 2016-04-06 | 贵州帝三数字技术有限公司 | A kind of intelligent aerial photography shutter trigger |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2079743A1 (en) | 1993-04-03 |
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