The links posted below are for a map created using ERDAS IMAGINE 2010 software and the ground control points as part of the University of West Florida On-line Geographic Information Systems (GIS) Certification program class, Photo Interpretation and Remote Sensing (GIS4035/L). The links require Internet Explorer to open and display properly.
This week's lab objective is learning to use control points from one image or map to rectify another image. In this case we were provided a USGS map of Pensacola as our ground control point source.In the "real" world, one always wants to check and recheck work before it is submitted. This is a little bit of a challenge since the image is a much coarser resolution than what seems to be available on the map. In this case the ground "truth" comes from the map. So once I was satisfied with the selection of the WHICH points were to be used I let the imagery point position float until I was satisfied with the visual position and RMS error. Click here for a view the ground control point results.
Fast forward to the completed image you see below (left side). The RMS was excellent, (<1), the coordinates seemed right so one more step was taken. The rectified image and the map image were placed in separate windows, linked and inquire cursors activated. Voila a perfect match. I could also have dropped them in the same window and looked to see how they overlaid each other but that will have to be for another day.
Look at the cross hairs on both images. They are centered on the runway intersections
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