Geometric rectification

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# Geometric rectification - PowerPoint PPT Presentation

Geometric rectification. Homework 6. 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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## PowerPoint Slideshow about 'Geometric rectification' - mahsa

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### Geometric rectification

Homework 6

CE403, 2008

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
• Due: April 1 (Tuesday), 2008

CE403, 2008

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

CE403, 2008

For the “geometric rectification” project, check

FieldGuide: Chapter 9

TourGuide: Chapter 6

One-line manual :

CE403, 2008

### A worked example – tutorial

Landsat image is to be rectified

based on SPOT image, Atlanta

CE403, 2008

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

D:\IMAGINE 8.6\examples\tmAtlanta.img

CE403, 2008

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

CE403, 2008

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)

CE403, 2008

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.

CE403, 2008

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.

CE403, 2008