ArcInfo ascii file format

ArcInfo ascii file format

Written by Paul Bourke
September 2021

The file format described here was developed by ArcInfo as a simple interchange format for digital terrain models (DTM). It is entirely ascii, human readable, text. It is only suited to regularly spaced grids. The first 6 lines of the file contain useful information required to successfully interpret the grid. The elevations at each grid point follow until the end of the file.

The six line header is as follows:

ncols         12751
nrows         9601
xllcorner     799997.5
yllcorner     799997.5
cellsize      5
NODATA_value  -9999

The array of elevation values following this header are ordered by columns (easting) and then by rows (northing).

Example of a 5m grid DTM of Hong Kong