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Geometric rectification

Geometric rectification. Homework 5. Description. Objective: geometrically rectify a portion (2km*2km) of SPOT image over West Lafayette area Reference (GCP): to be measured from the USGS digital ortho quad (DOQ). DOQ is used as the reference image Methodology: see the example

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Geometric rectification

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  1. Geometric rectification Homework 5 CE497 Urban Remote Sensing, Jie Shan

  2. Description • Objective: geometrically rectify a portion (2km*2km) of SPOT image over West Lafayette area • Reference (GCP): to be measured from the USGS digital ortho quad (DOQ). DOQ is used as the reference image • Methodology: see the example • Requirements: • at least 10 GCP and 6 check points need to be measured • 10 meter spatial resolution for the rectified image • Use and compare affine, polynomial (2nd order), projective transform (2nd order) methods • Data: ftp://ftp.ecn.purdue.edu/jshan/ce497URS/ • Hand in: a report including (max. 3 pages, 12 font, 1.5 line spacing) • A brief description of the principles of the used methods • Compare the results from different methods • The rectified image with coordinate grid and scale info in Letter format • Show and discuss your selected GCP and their residuals • Show and discuss your check points and their differences • Discuss and summarize your findings CE497 Urban Remote Sensing, Jie Shan

  3. Where to get help ? – pdf’s • FieldGuide: photogrammetry principles • TourGuide: step-by-step tutorial by modules • OrthBASE: orientation, matching, triangulation, DEM generation • StereoAnalyst: feature collection, stereo map compilation CE497 Urban Remote Sensing, Jie Shan

  4. For the “geometric rect.” project, Read: One-line manual : FieldGuide: Vol. 1 TourGuide: step by step CE497 Urban Remote Sensing, Jie Shan

  5. A worked example – tutorial Landsat image is to be rectified based on SPOT image, Atlanta CE497 Urban Remote Sensing, Jie Shan

  6. Image to be rectified – Landsat TM To display only one band, use Raster > Band Combinations dialogue box as below Choose one desired band to display CE497 Urban Remote Sensing, Jie Shan

  7. Reference image – SPOT Pan • Load the SPOT Pan image in a separate viewer. • This image will be used as a reference image, i.e., any location on this image can be used as (2-D) ground control. D:\IMAGINE\examples\ panAtlanta.img CE497 Urban Remote Sensing, Jie Shan

  8. Steps for geometric rectification • In the first view (the image to be rectified), run Raster > Geometric Correction command • Choose Polynomial in the Select Geometric Model dialogue box, select the polynomial order then click OK. • Click Close for now as below. (will make selection later) CE497 Urban Remote Sensing, Jie Shan

  9. Steps for geometric rectification Choose OK in the right window (Existing Viewer is checked) At the following prompt, Click the second viewer (the one to be used as reference). This step let you choose the reference image. CE497 Urban Remote Sensing, Jie Shan

  10. Steps for geometric rectification • Measure GCP. Note measure the 1st image (image to be rectified) first, and then the 2nd image (the reference image) • 1st and 2nd polynomials can be tested. Rarely go beyond 2nd order. However, you can test what happens if so is chosen. • Measure a number of check points to evaluate the quality of rectification (set the point type from the “GCP Tool” menu: edit > set point type > check) • Analyze the error distribution and decide if more GCPs are needed and where. • Produce the image map using the resample tool. • Check the on-line TourGuide for details. CE497 Urban Remote Sensing, Jie Shan

  11. Options for Projective Transform Model • At least 9 GCPs are required to solve the 2D model (using the same denomination for x and y –default option-) • Choose “Projective Transform” in the “Set Geometric Model” dialogue box, select the RPC order, check “2D Dimension Projective Model” option and make sure that the “Use same denominator for x and y” option is checked. • Click Close CE497 Urban Remote Sensing, Jie Shan

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