Principal Components in ER Mapper

To display "Principal Component" in ER Mapper complete the following steps on a new pseudocolor algorithm. You can make more than one PC and display them as rgb images. Note that you must run statistics on the dataset before you can do PC analysis. To run statistics, close all open windows and then choose Calculate Statistics from the Process menu. Select your filename.ers dataset and choose OK.  If you've done it before but want to get a "finer" resolution, enter 1 for sampling and click the force... button on.
  1. Open a new pseudocolor algorithm
  2. From the process stream open a dataset (like the AZ TM scene or the Va TM scene).
  3. Open the equation editor and choose the PC1 for Landsat TM option from the Principal Components Menu. The following equation will appear. The last number (which here appears as 4) tells you which PC is displayed. Edit it if you want to display PC's 2 through 6. Make sure that "input1" through "input6" refer to bands 1-5 & 7 respectively (band 6 is generally omitted due to the degraded resolution and lower information content).

  4. Click on "apply changes" and GO with 99% limits.
this collection illustrates the PC's from the AZ subscene

Using PC1 as an enhancement in another RGB image.

If you make a RGB ratio ( using 3 ratios) or RGB_PC2,PC3,PC4 image, there won't be much topographic information. To aid in locating yourself, add a new intensity layer (not surface) to the algorithm. In that intensity layer, omplete the above (2-4) instructions and leave it as PC 1. This will greatly enhance the visibility of the image. You may want to adjust the contrast stretch (often I increase the output lower limit by typing in 50-100, to keep it lighter colored

You can also layer two surfaces and see them by adjusting the transparency.
Here's how to do that.