Introduction

The only way to really become familiar with satellite imagery is to view the imagery in a variety of different ways. By doing this you can learn to observe important trends and patterns in the wealth of information stored in each image you look at. This tutorial is designed to help you learn how to visualize your imagery with the use of a free tool developed by ERDAS® Inc. called ERDAS® ViewFinder. It will also cover some basic steps for saving and printing your imagery in ERDAS® Mapsheets Express.

If you have not downloaded either ViewFinder or Mapsheets Express, you may wish to start with the Downloading Remote Sensing Software tutorial.

This tutorial uses a sample data set of a subset Landsat 7 image and a subset of a US Census roads layer. Click on the following links to download the four files:

Data files required for ViewFinder Tutorial
tutorial_l7.tif
roads.dbf
roads.shp
roads.shx

Starting ERDAS® ViewFinder

1. Click on the viewfinder icon on your desktop to start the program. The program will prompt you to choose a file to view.


2. Open the pulldown menu at the bottom labeled "files of type:," and choose TIFF (*.tif).


3. Navigate to the file "tutorial_l7.tif" and click on the file once to highlight it.


4. Before opening the image, click on the display options tab at the top of the dialog. Change the options so that a true color image will display by choosing the red color to display Layer_3, the green color to display Layer_2, and the blue color to display Layer_1. We will learn later how to change these at any point in the session.


5. While still in the display options dialog, click the box next to the automatically stretch contrast so that it is turned off.


6. Click OK to apply these options and display the image. It should look like this.


7. The image will be displayed in three separate views. These views work together in order to make viewing the image easier.

Main view: The main view is in the large right-hand window. This is the view you will use most often. It is best for seeing the whole of an area you are particularly interested in.

Location view: The small view in the upper left corner is the location view. This view always shows the entire image you have loaded into Viewfinder. It is geographically linked to the main view, so that you can always see where the main view is located in relation to the entire image. We will explore this more later.

Detail view: The detail view is located in the bottom left corner. This view is linked to the main view, and shows a magnified section of a selected area in the main view.