Geographic Information System

5 foot contours were produced from aerial photography projects in June 1999 and June 2001 . The contours are in the \DEM\5_foot_contours folder. We received 183 tiles in AutoCAD format from the photogrammetrists, which have been aggregated and converted into six MapInfo tables: Contours39N, Contours40N, Contours41N, Contours42N, ContoursAtla, and ContoursBufVal. Kelly is in Contours42N.

The contours have two attributes: "Elev", and "Type". Elev is the orthometric height in feet, on the North American Vertical Datum of 1929 (NAVD29), which is a fancy way of saying "elevation". The Type attribute is a three character field.

The first character of the type field is either an "X" or an "I". "X" contours are at 25 foot intervals, while "I" contours are the intermediate 5 foot contours. You can query for type "X" contours if you want to make a map showing just 25 foot contours. This would be useful when 5 foot contours are too dense.

The second character of the type field is either "O" or is blank. "O" stands for obstructed; where vegetation made it difficult for the photogrammetrist to see the ground. These contours are less reliable.

The third character of the type field is either "D" or blank. Type "D" contours are depression contours (holes).