Lab 3: Polynomial Rectification (Due by 4pm Feb 8)

Introduction

In this lab you will learn how to georeference a satellite image in Erdas Imagine.  

Instructions

Review pages 382 to 391 and pages 394 to 397 in the ERDAS Field Guide. For this lab, you will use a SPOT panchromatic image (panAtlanta.img) as the reference image to rectify a TM image (tmAtlanta.img). Strictly speaking, the reference image used in image rectification must have a map coordinate system defined. The target is an image that has only a file coordinate system (i.e., row and column). You can use the layer information tool to view the projection information of these image files.

The lab files are in I:\Students\Instructors\Geoffrey_Duh\GEOG4581\Lab3. Again, copy the lab folder to your workspace in the C:\users folder. Complete the tutorial exercise in the Polynomial Rectification section (pages 149 to 164) of the lab book (TourGuide9_1.pdf) and produce a map composition with three map frames, the unrectified TM image (tmAtlanta.img), the reference image (panAtlanta.img) and the georeferenced image (tmAtlanta_georef.img). You must clearly label each map. Put your name on the map and submit the map with your report.

Make sure you uncheck the “Orient Image to Map System” on the Raster Option tab when you open the rotated/flipped/stretched images. Produce a map that display tmAtlanta_georef.img and tmAtlanta_rotate.img side by side. Label each map, put your name on the map, and submit the map with your report.

Answer the following questions.

1. What is a transformation matrix?
2. How many GCPs are necessary when doing a 1st order transformation and how do you calculate it?
3. What is the map projection of your rectified file?
4. Write one paragraph directed at the lay person explaining what georeferencing is all about and how you do it.