TOPOGRAPHIC MEASUREMENT USING STEREOSCOPIC PICTURE FRAMES

• US 20080050009A1
• Filed: 10/15/2007
• Published: 02/28/2008
• Est. Priority Date: 06/20/2002
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: Makoto Maruya
• Inventors: Maruya, Makoto
• Granted Patent: US 7,508,972 B2
• Time in Patent Office: Days
• US Class Current: 382/144
• CPC Class Codes: G06T 7/55 from multiple images

Abstract

Disclosed is a topographic measurement system wherein at least one satellite is used to scan the earth surface and send picture frames of a target area captured at different positions to an earth station. The picture frames are combined to produce a number of pairs of frames which constitute a stereoscopic image of the target area. Each frame pair is analyzed according to a number of visual characteristics and evaluated with a set of fitness values representative of the degrees of fitness of the frame pair to topographic measurement of the target area. A total of the fitness values is obtained from each frame pair and compared with the total values of other frame pairs. A frame pair having the highest total value is selected as a best pair. A parallax between the best pair frames is determined to produce first and second sets of line-of-sight vectors for conversion to topographic data.

Claims

1. A topographic data processor comprising:

frame selecting means for selecting a pair of frames from a plurality of candidate picture frames of a target area captured from high-altitude positions, said selected pair of frames constituting a stereoscopic image of said target area;

scheduling means for selecting at least one airborne image sensor if an appropriate frame is not available in said plurality of candidate frames, sensing picture frames from the selected image sensor, whereby said frame selecting means uses the sensed frames to select a pair of frames;

means for determining a parallax between the frames selected by the frame selecting means and producing therefrom a first plurality of line-of-sight vectors and a second plurality of line-of-sight vectors; and

means for converting said first and second pluralities of line-of-sight vectors to topographic data.

2. A topographic data processor as claimed in claim 1, wherein said frame selecting means comprises:

means for combining the received picture frames to form a plurality of pairs of sensed frames which may constitute a stereoscopic image of said target area;

evaluating means for evaluating each pair of sensed frames with a fitness value indicative of fitness of said each pair of frames to topographic measurement of said target area; and

scheduling means for producing a schedule for sensing picture frames from one or more airborne image sensor based on fitness values obtained from all said pairs of sensed frames.

3. A topographic data processor as claimed in claim 2, wherein said evaluating means comprises a geometric condition analyzer for analyzing said pairs of sensed frames in terms of their geometric condition and evaluating said pairs of frames with a fitness value inversely proportional to quantum errors between the frames of each said pair.

4. A topographic data processor as claimed in claim 3, wherein said evaluating means further comprises filtering condition analyzing means for analyzing each of said pairs of sensed frames in terms of filtering condition and evaluating each said pair of sensed frames with a fitness value representative of filtering characteristics of image sensors.

5. A topographic data processor as claimed in claim 3, wherein said evaluating means further comprises sunlight condition analyzing means for analyzing each of said pairs of sensed frames in terms of sunlight condition and evaluating each said pair of sensed frames with a fitness value representative of degree of similarity in shadow and shading effects between the frames of each said pair.

6. A topographic data processor as claimed in claim 3, wherein said evaluating means further comprises time difference analyzing means for analyzing each of said pairs of sensed frames in terms of time difference and evaluating each said pair of sensed frames with a fitness value inversely proportional to a time difference between the instant one of the frames of said each pair is captured and the instant the other frame is captured.

7. A topographic measurement system comprising:

at least one image sensor mounted on a vehicle flying over a target area;

means for sensing a plurality of picture frames at different positions by using said image sensor;

means for selecting a pair of frames from said plurality of frames, said pair of frames constituting a stereoscopic image of said target area;

means for determining a parallax between the selected frames and producing therefrom a first plurality of line-of-sight vectors and a second plurality of line-of-sight vectors; and

means for converting said first and second pluralities of line-of-sight vectors to topographic data.

8. A topographic measurement system as claimed in claim 7, wherein said frame selecting means comprises:

frame combining means for combining said candidate frames into a plurality of pairs of frames which constitute a stereoscopic image of said target area;

evaluating means for evaluating each of said pairs of frames with a fitness value indicative of fitness of said each pair of frames to topographic measurement of said target area; and

decision means for selecting one of said pairs of frames based on fitness values obtained from all said pairs of sensed frames.

9. A topographic measurement system as claimed in claim 8, wherein said evaluating means comprises:

a geometric condition analyzer for analyzing said pairs of frames in terms of their geometric condition and evaluating said pairs of frames with a fitness value proportional to their image resolution; and

decision making means for making a decision on the fitness values obtained by all pairs of frames and selecting one of said pairs of frames having the highest fitness value.

10. A topographic measurement system as claimed in claim 9, wherein said parallax determining means determines a parallax between the frames of each said pair of frames, and

wherein said evaluating means further comprises frame matching analyzing means for analyzing said pairs of frames in terms of degree of match between the paired frames and evaluating said pairs of frames with a fitness value proportional to an average value of point-to-point correlations between said paired frames,

wherein said decision making means produces a total value of the fitness values of each of said pairs of frames and selecting one of said pairs of frames having the highest total value.

11. A topographic measurement system as claimed in claim 8, wherein said parallax determining means comprises:

frame aligning means for aligning the frames of said selected pair in orientation; and

correlation calculating means for calculating point-to-point correlations between the aligned frames.

12. A topographic measurement system as claimed in claim 10, wherein said parallax determining means comprises:

frame aligning means for aligning the frames of said selected pair in orientation; and

correlation calculating means for calculating point-to-point correlation values between the aligned frames and supplying the calculated correlation values to said frame matching analyzing means, and

wherein the frame matching analyzing means calculates said average value of point-to-point correlations from the correlation values supplied from the correlation calculating means.

13. A topographic measurement system as claimed in claim 10, wherein said parallax determining means further comprises an interpolator for interpolating one of the paired frames before said frames are aligned in orientation so that said frames of said pair have equal value of resolution.

14. A topographic measurement system as claimed in claim 8, wherein said evaluating means further comprises filtering condition analyzing means for analyzing each of said pairs of frames in terms of filtering condition and evaluating each said pair of frames with a fitness value representative of filtering characteristics of image sensors.

15. A topographic measurement system as claimed in claim 8, wherein said evaluating means further comprises sunlight condition analyzing means for analyzing each of said pairs of combined frames in terms of sunlight condition and evaluating each said pair of frames with a fitness value representative of degree of similarity in shadow and shading effects between the frames of each said pair.

16. A topographic measurement system as claimed in claim 8, wherein said evaluating means further comprises time difference analyzing means for analyzing each of said pairs of combined frames in terms of time difference and evaluating each said pair of frames with a fitness value inversely proportional to a time difference between the instant one of the frames of said each pair is captured and the instant the other frame is captured.

17. A topographic measurement system as claimed in claim 7, further comprising storage medium for storing a plurality of picture frames captured by airborne image sensors, wherein said selecting means selects said pair of frames from said storage medium.

18. A topographic measurement system as claimed in claim 17, wherein said frame combining means includes area selecting means for selecting frames covering said target area from all frames stored in said storage medium.

19. A topographic measurement system as claimed in claim 7, further comprising an image sensing scheduler comprising:

sensor selecting means for selecting at least one airborne image sensor if an appropriate frame is not available to constitute said stereoscopic image and sensing picture frames from the selected image sensor;

frame combining means for combining the received picture frames to form a plurality of pairs of sensed frames which may constitute a stereoscopic image of said target area;

evaluating means for evaluating each pair of sensed frames with a fitness value indicative of fitness of said each pair of frames to topographic measurement of said target area; and

scheduling means for producing a schedule for selecting one or more airborne sensors based on the fitness values obtained from all pairs of sensed frames.

20. A topographic measurement system as claimed in claim 19, wherein said evaluating means of said scheduler comprises a geometric condition analyzer for analyzing said pairs of sensed frames in terms of their geometric condition and evaluating said pairs of frames with a fitness value inversely proportional to quantum errors between the frames of each said pair.

21. A topographic measurement system as claimed in claim 20, wherein said evaluating means of the scheduler further comprises filtering condition analyzing means for analyzing each of said pairs of sensed frames in terms of filtering condition and evaluating each said pair of sensed frames with a fitness value representative of filtering characteristics of image sensors.

22. A topographic measurement system as claimed in claim 20, wherein said evaluating means of the scheduler further comprises sunlight condition analyzing means for analyzing each of said pairs of sensed frames in terms of sunlight condition and evaluating each said pair of sensed frames with a fitness value representative of degree of similarity in shadow and shading effects between the frames of each said pair.

23. A topographic measurement system as claimed in claim 20, wherein said evaluating means of the scheduler further comprises time difference analyzing means for analyzing each of said pairs of sensed frames in terms of time difference and evaluating each said pair of sensed frames with a fitness value inversely proportional to a time difference between the instant one of the frames of said each pair is captured and the instant the other frame is captured.

24. A topographic measurement system comprising:

at least one image sensor mounted on a vehicle flying over a target area;

means for sensing a plurality of picture frames at different positions by using said image sensor;

frame selecting means for selecting a pair of frames from said plurality of frames of said target area, said selected pair of frames constituting a stereoscopic image of said target area;

scheduling means for selecting at least one image sensor if an appropriate frame is not available in said plurality of frames, sensing picture frames from the selected image sensor, whereby said frame selecting means uses the sensed frames to select a pair of frames;

means for determining a parallax between the frames selected by the frame selecting means and producing therefrom a first plurality of line-of-sight vectors and a second plurality of line-of-sight vectors; and

means for converting said first and second pluralities of line-of-sight vectors to topographic data.

25. A topographic measurement system as claimed in claim 24, wherein said scheduling means comprises:

frame combining means for combining the received picture frames to form a plurality of pairs of sensed frames which may constitute a stereoscopic image of said target area;

evaluating means for evaluating each pair of sensed frames with a fitness value indicative of fitness of said each pair of frames to topographic measurement of said target area; and

decision means for producing a schedule for sensing picture frames from one or more airborne image sensors based on fitness values obtained from all of said pairs of sensed frames.

26. A topographic measurement system as claimed in claim 25, wherein said evaluating means comprises a geometric condition analyzer for analyzing said pairs of sensed frames in terms of their geometric condition and evaluating said pairs of frames with a fitness value inversely proportional to quantum errors between the frames of each said pair.

27. A topographic measurement system as claimed in claim 26, wherein said evaluating means further comprises filtering condition analyzing means for analyzing each of said pairs of sensed frames in terms of filtering condition and evaluating each said pair of sensed frames with a fitness value representative of filtering characteristics of image sensors.

28. A topographic measurement system as claimed in claim 26, wherein said evaluating means further comprises sunlight condition analyzing means for analyzing each of said pairs of sensed frames in terms of sunlight condition and evaluating each said pair of sensed frames with a fitness value representative of degree of similarity in shadow and shading effects between the frames of each said pair.

29. A topographic measurement system as claimed in claim 26, wherein said evaluating means further comprises time difference analyzing means for analyzing each of said pairs of sensed frames in terms of time difference and evaluating each said pair of sensed frames with a fitness value inversely proportional to a time difference between the instant one of the frames of said each pair is captured and the instant the other frame is captured.