1 / 26

Photogrammetry & Image Analysis

Photogrammetry & Image Analysis . Photogrammetry. Originally, the science (or art?) of interpreting aerial photographs Stress on quantitative measurements Now includes analysis of digital images from many sources. Image from Avery. Interpretation of Aerial Photographs.

tabitha
Download Presentation

Photogrammetry & Image Analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Photogrammetry & Image Analysis CS 128/ES 228 - Lecture 9b

  2. Photogrammetry • Originally, the science (or art?) of interpreting aerial photographs • Stress on quantitative measurements • Now includes analysis of digital images from many sources Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  3. A hierarchy of remote sensing • Satellite sensing • Aerial photography • Ground-truthing Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  4. Perspectives • Vertical:- orthogonal perspective- planimetric map data • Oblique: - high oblique (includes horizon) - low oblique (no horizon) Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  5. Scale Determine from: • Plane altitudeRF = lens focal length altitude of plane • Known ground features Top image from Avery. Interpretation of Aerial Photographs. Bottom images from Ben Meadows catalog (L), Olean NW DOQQ ® CS 128/ES 228 - Lecture 9b

  6. Problems Plane altitude • determining altitude (barometer, radar altimeter) • variation among photos • uneven terrain Known ground features: need • objects of known size & large enough for accurate measurement, or • pair of points for distance measure CS 128/ES 228 - Lecture 9b

  7. Planimetric view • Perfectly vertical (orthogonal) perspective • All features in correct horizontal positions • Impossible unless at infinite height CS 128/ES 228 - Lecture 9b

  8. The principle point • Point directly under camera lens (‘nadir’) • Elevated objects lean away from PP • Depressed objects lean toward PP • Causes image displacement Images from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  9. Vertical relief causes displacement • Transmission line is straight - why does the line appear straight in one photo and jagged in second? • In left stereogram, line is ~ on nadir; in right stereogram, far from nadir Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  10. Image displacement: • Source of error in horizontal locations, but • Permits estimation of feature elevations stereoscopic parallax Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  11. Stereoscopic photo pairs Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  12. Stereoscopes • need pair of overlapping photos • different principle points results in parallax • used to create topographic contours CS 128/ES 228 - Lecture 9b

  13. Shadows • Need sun angle • Object must be vertical • Shadow must come from top and fall on level ground • H = L x tan(α) Image from Avery. Interpretation of Aerial Photographs.\ H = L x tan(α) CS 128/ES 228 - Lecture 9b

  14. Rectification of aerial photographs Rectification: process of geometric correction that turns an aerial photograph into a planimetric (map-like) image Problems: • lens distortion • Earth curvature • camera tilt • terrain relief CS 128/ES 228 - Lecture 9b

  15. Rectification process • Scan aerial photograph at high resolution • Locate ground control points on scanned image: ≥3 for affine transformation ≥5 for rubbersheeting • Combine with DEM to correct relief displacement • Rectify to a ground coordinate system CS 128/ES 228 - Lecture 9b

  16. Relief distortion Objects at different distances form the lens will be distorted CS 128/ES 228 - Lecture 9b

  17. Result: digital orthophotograph • USGS supplies in DOQ format • NYS GIS site provides freecolored infrared DOQQs CS 128/ES 228 - Lecture 9b

  18. Urban areas: building tilt In urban areas, tall buildings seem to lean toward the principal point of the photograph Corrected by building a DTM of each building Permits virtual reality “flyovers” Thorpe, A. Digital orthophotography in New York City. www.sanborn.com/Pdfs/Article_DOI_Thorpe.pdf CS 128/ES 228 - Lecture 9b

  19. Image Analysis • Identification of objects • Assigning attributes to objects or areas • Assessing the significance of patterns • Can be: • Visual interpretation • Computer-assisted image analysis CS 128/ES 228 - Lecture 9b

  20. Landsat Images • Landsat 1-4 launched 1972 – ’82; expired • Landsat 5 & 7 launched 1985 & 1999; both operational • TM: thematic mapper. - 7 spectral bands- designed primarily for ES themes http://landsat.gsfc.nasa.gov/project/L7images.html CS 128/ES 228 - Lecture 9b

  21. TM Applications CS 128/ES 228 - Lecture 9b

  22. Hydrology example Images from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 9b

  23. Terra (and EOS) • Terra launched • Carries 5 instruments; the MSS imager is called ASTER (from Japan) • 14 spectral bands:- 3 VIS/near IR (15 m)- 6 short IR (30 m)- 5 thermal IR (90 m) Images from www.nasa.gov CS 128/ES 228 - Lecture 9b

  24. ASTER spectral signature library “Welcome to the ASTER spectral library, a compilation of almost 2000 spectra of natural and man made materials.” http://speclib.jpl.nasa.gov CS 128/ES 228 - Lecture 9b

  25. Classification schemes 1.a Unsupervised: raw data analyzed for clusters 1.b Supervised: prior categories imposed 2. Classification of new data 3. Ground truthing … Lo & Yeung. Concepts and Techniques of Geographic Information Systems CS 128/ES 228 - Lecture 9b

  26. And that’s the fun part … CS 128/ES 228 - Lecture 9b

More Related