Lab 6: Geometric Correction

Goal and Background:
The purpose of this lab was to learn geometric correction skills using image-to-map rectification and image-to-image registration.

Methods:
PART 1 - Image-to-Map Rectification
I brought in a satellite image and a map of the Chicago area in to Erdas. I activated the Multispectral raster processing tool and clicked on Control Points where a pop-up menu appeared and I then selected Polynomial under the Select Geometric Model. I then accepted the default parameters in the GCP Tool Reference Setup. I started to collect my GCPs from the map image where I used the Create GCP tool. I first collected four GCPs where I then adjusted my GCPs until my Total Control Point Error (RMS error) was less than 2.0, and I strived to get below 0.5. Next I used the Display Resample Image Dialog tool to create an adjusted image.

PART 2 - Image-to-Image Registration
This part of the lab was much like the first part, but instead of a 1st order polynomial, I used a 3rd order polynomial for this part where I needed a minimum of ten GCPs instead of a minimum of three. However, I chose to use 12 GCPs just to be on the safe side. I then used the Display Resample Image Dialog tool to create an adjusted image and changed the resampling method to Bilinear Interpolation.

Results:

Sources:
Satellite images are from Earth Resources Observation and Science Center, United States Geological Survey. Digital raster graphic (DRG) is from Illinois Geospatial Data Clearing House.