Geography 338: Remote Sensing: Lab 6

Goals and Background

The purpose of this lab was to learn how to preform geometric correction on an image. There were two forms of rectification in this lab

1. Image to map rectification
2. Image to image rectification

Methods

For Image to map rectification

1. First the images Chicago_2000.img and Chicago_drg.img were brought into the two viewers. Then I clicked on multispectral and Control Points.

2. I selected Polynomial for the geometric model, in the next window I accepted the default Image Layer(New Viwer) in the GCP Tool Reference Setup. I then selected Chicago_drg.img as my reference image. After this step I accepted all of the default properties.

3. I deleted the default GCPs and selected my own. For the equation being used only 3 pairs of GCPs were needed, but 4 were selected.

GCP points on Reference image shown on the right and input image shown on the left

4. The GCP points were moved around until the total RMS error (shown at the bottom of the screen) was less than .5

Total RMS error shown at bottom of the screen

5. I then clicked on the Display Resample Image Dialog button, I named the output file Chicago_2000gcr.img and saved it to my Lab 6 folder. I left all of the default parameters and executed the geometric correction.

For Image to Image rectification

The process was similar to the image to map rectification. For my reference image I used Sierra_Leone_east1991grf.img and for my input image I used Sierra_leone_east1991.img. The only differences in the process were as followed

1.Under the polynomial model properties I changed the polynomial order to 3

2. 12 GCP pairs were used to account for the higher polynomial order

3. The resample method was changed to bilinear interpolation

Results

The resulting geometrically corrected images can be seen below