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 4 - Georeference the Image

An image is a lot more useful when it's transformed to fit into a standard map projection system (one we often use is Universal Transverse Mercator, or UTM). We do this by georeferencing the image using some source of independent location control -- for example, topographic maps, digital roads, or ground control points measured using GPS receivers. In this example, location control is provided using roads depicted on 1:100,000 scale Digital Line Graph (DLG) data downloaded from the US Geological Survey that are accurate to within 100 meters. Prominent road junctions are located throughout the image, and their map locations measured from the DLG file. Once a suitable set of location control points is defined in this way, the image data are then digitally “resampled” to fit a desired map projection.

The map-projected image now can be combined with other types of spatial data using Geographic Information Systems (GIS) software and analysis techniques. Georeferencing is a critical step for creating a useful image product.