In the broadest sense, digitizing refers to any process that converts nondigital data into numbers. However, in ERDAS IMAGINE, the digitizing of vectors refers to the creation of vector data from hard-copy materials or raster images that are traced using a mouse on a displayed image.
Any image not already in digital format must be digitized before it can be read by the computer and incorporated into the database. Most Landsat, SPOT, or other satellite data are already in digital format upon receipt, so it is not necessary to digitize them. However, you may also have maps, photographs, or other nondigital data that contain information you want to incorporate into the study. Or, you may want to extract certain features from a digital image to include in a vector layer. Digitizing enables you to digitize certain features of a map or photograph, such as roads, bodies of water, voting districts, and so forth.
In screen digitizing, vector data are drawn with a mouse in the Viewer using the displayed image as a reference. These data are then written to a vector layer.
Screen digitizing is used for the several purposes:
- digitizing roads, bodies of water, political boundaries
- selecting training samples for input to the classification programs
- outlining an area of interest for any number of applications
Create a new vector layer from File button in ERDAS IMAGINE Workspace.