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Geometric rectification

Homework 6

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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 6 GCP and 6 check points need to be measured 10 meter spatial resolution for the rectified image

Data: ftp://ftp.ecn.purdue.edu/jshan/ce403/project6/ Hand in: a report including (max. 4 pages, 12 font, 1.5 line spacing)

A brief description of the work The rectified image with coordinate grid (you may use ArcView or

ArcGIS for output) and scale info in Letter format Layout of your selected GCP and their residuals Layout of your check points and their differences Evaluation/discussion on your results

Due: April 1 (Tuesday), 2008

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Where to get help ? - Pdf documents

FieldGuide: photogrammetry principles

TourGuide: step-by-step tutorial by modules

OrthBASE: orientation, matching, triangulation, DEM generation

StereoAnalyst: feature collection, stereo map compilation

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Where to get help ? on-line manual

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For the “geometric rectification” project, check

FieldGuide: Chapter 9

One-line manual :TourGuide: Chapter 6

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A worked example – tutorial

Landsat image is to be rectified

based on SPOT image, Atlanta

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Choose one desired band to display

Image to be rectified – Landsat TM

To display only one band, use Raster > Band Combinations dialogue box as below

D:\IMAGINE 8.6\examples\tmAtlanta.img

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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 8.6\examples\panAtlanta.img

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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, then click OK.

Click Close for now as below. (will make selection later)

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Steps for geometric rectification

Choose OK in the right window (Existing Viewer is checked)

At the following prompt, Click the second viewer (the oneto be used as reference). This steplet you choose the reference image.

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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

Analyze the error distribution and decide if more GCPs are needed and where.

Check the on-line TourGuide for details.