1.  Open ERDAS IMAGINE from your desktop

2.  In the Viewer window go to File --> Open --> Raster Layer.....   and find the bbcgis folder.  Open the "pnw98_bbg.img" file from the folder. 

3.  Click on the image with the right mouse button and choose "Fit Image to Window" from the menu that appears. 

4. Click on the classifier icon from the icon pane Select Unsupervised classification, the dialog opens

5. Complete the Input window option.

NOTE: Input raster file (*.img) and provide an output name. You can output a signature file. Initial clusters can be generated either arbitrarily or from an existing signature mean. You can select to initial from statistics

• Enter the number of different NUMBER OF CLASSES (ie. Try 9)
• Set the maximum iterations up to 15 (this insure the process will not run on forever)
• Set the convergence threshold to .95 (ie. Stop processing when 95% of the pixels stay in the same cluster between interations)

Click OK on the dialog and on the status dialog when the process is completed.

6. When the process is completed open a second viewer and load the new image.

7. Remember; the image is now a single dimension where each pixel has a value between 1-9 which assigns that pixel to a cluster of similar pixels. This image is a RASTER data layer. It therefore has "attributes". From the viewer #2 select RASTER > ATTRIBUTE and click on one of the shaded cells to change the color attribute for that attribute.

8. Make a color selection for the other pixel values. Remember that you can geo-link to the other view to help you understand what the clustered values might mean.

9. One very nice function that helps evaluate clusters and/or classes is to visually overlay images. Make sure you have a view with the spectral image file opened (file >open > raster layer and display bands 4,5,3 respectively

10. from that viewer tool bar open a classified raster layer, make sure the "clear display" option is turned off from the "raster options tab" found from that dialog box select Raster > Attributes from the viewer, the editor will be displayed

11. NOTE: you can edit the way this editor appears by selecting Edit > Column Properties

12. Start by setting opacity for all classes to "0". In the Raster Attribute Editor, click on the word OPACITY at the top of the Opacity column, then right-click-hold on the word Opacity and select formula from the column option menu, click on the "0" (the zero on the number pad); and click on Apply.

13. If you have not already change the color for class 1 do so now - to something like Yellow or red so it's easier to see, … click on the color patch and change the color.

Change the opacity for class 1 in the Cell Array to 1 and press return, this class will be shown in the viewer. Also, change the opacity for class 7.

14. From the viewer menu bar select Utility |> Flicker … the dialog opens … turn on the auto mode. The flashing pixels are the pixels in this class, click on the Class_Name in the editor and give it meaningful name and assign it a meaningful color . Repeat for the other classes.

15. Now you go figure out what Utility > Swip and Utility > Blend will do.

IMPORTANT:  When you close ERDAS, you will be asked if you want to print the Log File.  Say NO!