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Photogrammetry

Photogrammetry

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Photogrammetry

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  1. Photogrammetry • Quantitative Measurements from Aerial Photography • Flightlines of Vertical Aerial Photography • Stereoscopic Vision and Stereoscopes • Photo Alignment for 3D Visualization • Orthophotographs and DEMs • Reminder: Read Chapter 7 (pp. 193-218) for next class

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  3. What Quantitative Measurements can be obtained from a Single Vertical Aerial Photograph? • Scale • Object length • Area of photography or feature • Perimeter of feature

  4. What Quantitative Measurements can be obtained using Overlapping Stereoscopic Aerial Photographs • Precise planimetric locations • Precise object height • Planimetrically accurate orthophotographs • Digital Elevation Models (DEMs) • Slope and aspect derived from DEMs

  5. Flightline of Vertical Aerial Photography Jensen, 2000

  6. Block of Vertical Aerial Photography Jensen, 2000

  7. Block of Vertical Aerial Photography Compiled into an Uncontrolled Photomosaic Columbia, SC Original scale = 1:6,000 Focal length = 6” (152.82 mm) March 30, 1993 Jensen, 2000

  8. Flightline #4 Photo #5 Columbia, SC Original scale = 1:6,000 Focal length = 6” (152.82 mm) March 30, 1993 Jensen, 2000

  9. Geometry of Overlapping Vertical Aerial Photographs • Principal Points • Conjugate PrinciplePoints Jensen, 2000

  10. Geometry of A Vertical Aerial Photograph Obtained Over Flat Terrain

  11. Geometry of A Vertical Aerial Photograph Collected Over Flat Terrain Jensen, 2000

  12. Enlargement of A Portion of Flightline #4, Photo #5 Jensen, 2000

  13. Geometry of A Vertical Aerial Photograph Collected Over Variable Relief Terrain Jensen, 2000

  14. Measurement of Object Height From A Single Aerial Photograph Based on Relief Displacement Line of flight Jensen, 2000

  15. Measurement of Object Height From A Single Aerial Photograph Based on Shadow Length on Level Terrain Sun’s rays Jensen, 2000

  16. Stereoscopic Vision What is stereoscopic vision and what is its significance for remote sensing?

  17. Stereoscopic Vision • 3-D effect occurs when an object is viewed from two different, but overlapping, viewpoints • Human eyes – up to ~1,000 m • Aerial photography – two successive aerial photos with at least 60% forward overlap will provide stereoscopic aerial photography • Basis for 3-D effect

  18. Parallactic Angles Used During Depth Perception 0.119” 59.1’ Jensen, 2000

  19. Stereoscopic Viewing Methods Jensen, 2000

  20. Stereoscopes • Deflect our normally converging lines of sight so each eye views a different image • Lens (pocket) stereoscope • Reflecting stereoscope • Zoom stereoscope • Stereoplotters

  21. Photo Alignment • Identify principal point of each photograph • Locate conjugate principal point (or point(s) that corresponds to principal point on adjacent photos) • Align points with flight line (straight line)

  22. Geometry of Overlapping Vertical Aerial Photographs • Principal Points • Conjugate PrinciplePoints Jensen, 2000

  23. Lens Stereoscope with Parallax Bar Jensen, 2000

  24. Stereoscopic Parallax Principles Jensen, 2000