Geometric rectification Homework 5 CE 497 Urban Remote

Geometric rectification Homework 5 CE 497 Urban Remote Sensing, Jie Shan 1

Description n Objective: geometrically rectify a portion (2 km*2 km) of SPOT image over West Lafayette area n Reference (GCP): to be measured from the USGS digital ortho quad (DOQ). DOQ is used as the reference image n Methodology: see the example n Requirements: n n n 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 (2 nd order), projective transform (2 nd order) methods n Data: ftp: //ftp. ecn. purdue. edu/jshan/ce 497 URS/ n Hand in: a report including (max. 3 pages, 12 font, 1. 5 line spacing) n n n 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 CE 497 Urban Remote Sensing, Jie Shan 2

Where to get help ? – pdf’s n n Field. Guide: photogrammetry principles Tour. Guide: step-by-step tutorial by modules Orth. BASE: orientation, matching, triangulation, DEM generation Stereo. Analyst: feature collection, stereo map compilation CE 497 Urban Remote Sensing, Jie Shan 3

For the “geometric rect. ” project, Read: One-line manual : Field. Guide: Vol. 1 Tour. Guide: step by step CE 497 Urban Remote Sensing, Jie Shan 4

A worked example – tutorial Landsat image is to be rectified based on SPOT image, Atlanta CE 497 Urban Remote Sensing, Jie Shan 5

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 CE 497 Urban Remote Sensing, Jie Shan 6

Reference image – SPOT Pan n Load the SPOT Pan image in a separate viewer. n 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: IMAGINEexamples pan. Atlanta. img CE 497 Urban Remote Sensing, Jie Shan 7

Steps for geometric rectification n In the first view (the image to be rectified), run Raster > Geometric Correction command n Choose Polynomial in the Select Geometric Model dialogue box, select the polynomial order then click OK. n Click Close for now as below. (will make selection later) CE 497 Urban Remote Sensing, Jie Shan 8

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. CE 497 Urban Remote Sensing, Jie Shan 9

Steps for geometric rectification n Measure GCP. Note measure the 1 st image (image to be n n n rectified) first, and then the 2 nd image (the reference image) 1 st and 2 nd polynomials can be tested. Rarely go beyond 2 nd 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 Tour. Guide for details. CE 497 Urban Remote Sensing, Jie Shan 10

Options for Projective Transform Model n At least 9 GCPs are required to solve the 2 D model (using the same denomination for x and y – default option-) n Choose “Projective Transform” in the “Set Geometric Model” dialogue box, select the RPC order, check “ 2 D Dimension Projective Model” option and make sure that the “Use same denominator for x and y” option is checked. n Click Close CE 497 Urban Remote Sensing, Jie Shan 11