Step 1
Load the image!

Step 2
Enhance contrast

Step 3
Select a band combination

Step 4
Georeference the image

Step 5
Enhance resolution

Step 6
Enhance sharpness

Step 7
Create maps and graphics

STEP 2 - Enhance Contrast

Contrast -- the range between light and dark objects in the image -- needs to be enhanced to emphasize color and brightness variations and minimize the dulling effect of atmospheric haze. This is done by digitally "stretching" the data so the pixels span the full range of possible brightness (many satellite images are composed of 8-bit data, a possible range of 2**8 or 256 brightness values). ETM images have eight different spectral bands that sample discrete portions of the electromagnetic spectrum ranging from visible wavelengths of light through thermal infrared “heat.”

The image shown on here is a “natural color composite” of ETM bands 3 (visible red light), 2 (green light), and 1 (blue light), displayed using the colors red, green and blue, respectively. Despite the name, this composite provides very poor color differentiation on satellite imagery.

Proper contrast enhancement makes a big difference!