Geographic Information Retrieval and Analysis System (GIRAS)
The GIRAS format involves a standard character fixed length record (usually ASCII-coded, 80 character card images). Each record may consist of 1 to 16 data-element fields. Each data-element field may be one of three different types: 1) 16 bit binary integer; 2) 32 bit binary integer or 3) a string of text characters. The GIRAS file structure is comprised of a map header, section header, arc records subfile, coordinate subfile, polygon records subfile, file of arcs by polygon (FAP) subfile, text subfile and an associated data subfile.
Composite Theme Grid (CTG)
The CTG files are sequential and consist of fixed length records (except for header files) with one grid cell for each logical record. The grid cells are actually a regular point sample of the quad where the center point of each cell is 200 meters apart from other center points in adjacent cells. The cells are mapped to the UTM projection, oriented in the north-south, east-west directions and sequenced by row from north to south, within each row, by column east to west.