The DEM used in this exercise has been geometrically corrected and resampled to 25 meter pixels. The DEM is from USGS. This DEM was chosen because of its unique topographic features.

DEM -- UNDERSTANDING RASTER IMAGERY

An image is a representation of some rectangular portion of space. Raster is a term used to describe a system for representing images. A raster image is composed of small cells (pixels) that are uniform in size and arranged in a grid. The resolution of an image is the spatial dimension of the pixel (density of data collection points). A digital elevation model (DEM) represents elevations of surface for every pixel. The following exercises will provide experience in using digital imagery.

1. Open ArcView -- Check the Spatial Analyst Extension
2. View the DEM as a tiff image.
3. Convert to a grid.
4. Data values in this file range from 77 to 164. Actual elevation values (in meters) can be calculated by adding that value to the base elevation of 1140 meters.
5. Create contour lines of 10 meters.
6. Make a separate view of elevations over 1295 meters.
7. Convert to a shapefile and create a layout showing the elevation map and the view containing elevations over 1295 meters with an appropriate scale, north arrow and titled with your names.