Lab 6

In lab 6 we used Image Geometric Correction to combine two images. In the first part of the exercise we use Image-to-mpa rectification. That is, we took a satellite image of the Chicago area and combined it with a USGS map of the same area. Below are the to images to be combined.

The USGS 7.5 minute digital raster graphic.

Satellite image.

Using Multipoint Geometric Correction we use the map as the reference image and the satellite image for the input image. We then select 4 Ground Control Points(GCP) spread out over the entire map to ensure all parts of the image are stretched and adjusted equally. We then must make sure that all 4 points are within an RMS error of <2.

Here is the image showing my RMS error of .402. The resulting image is below.

If you look closely the image is very similar to the original satellite image. Though some adjustments can be seen and the second image is not quite is high a quality in detail.

The second part of the lab was to use Image to image registration. This is the process of taking two images of similar geometry and the same geographic location and combining them.

The top map is the first image and is highly distorted. The distortion can be seen in the bottom image showing the better quality image overlaid on the poor image. This is done using the Swipe option in Erdas. Now to combine them using 12 GCP's.

The above image shows the GCP's applied to both images.