30 Arc Second Digital Elevation Data
This file discusses the programs and utilities for extracting and
processing data from the 30 Arc Second Digital Elevation Map of
the United States.
Unless otherwise noted:
- source code and makefiles are in /nfs/meter/home/cherkaue/source/dem
- executables are in /nfs/meter/home/cherkaue/bin/sun4
- 30 arc second data map is in /nfs/hydro4/usr2/lettenmaier/strip/tmp
File Contents
The following DEM files are located down /nfs/hydro4/usr2/lettenmaier/strip/tmp
- DEM.EL.dom - Original DEM (with pits)
- ELEV - Smoothed out DEM (without pits)
- MASK.dom - Mask file
Dimensions: 3240 cols x 8160 rows
Orientation: Pixel (1,1) is at the Northwest corner
LAT/LONG: Pixel (1,1) is at
- 50:59:30 N latitude
- 127:59:30 W longitude
The programs cut and cut-30 will extract a region from the US 30 arc second
DEM map. The program cut requires the region be defined in rows and columns,
while cut-30 will accept a region defined by latitude and longitude. The
output file will be an ASCII raster file, without a header.
The program cut.c extracts a specified subset of the U.S. dem, which is
at a resolution of thirty arc seconds per pixel. One pixel is about 900m,
i.e., 30.0 arc seconds ~ 900.0m. The output is an ascii file.
Each watershed that is delineated is identified in the mask file by an integer.
Each watershed has a unique number. The number associated with a particular
watershed of interest can be found by reviewing the file qall_num.dat.
This file is located in the directory "lettenmaier/strip/etc/basins". Not
all watersheds in the U.S. have been delineated at this scale. Those
watersheds which are solved are listed in the
file "lettenmaier/strip/etc/basins/solved.bas_id".
Hydrology Homepage /University of Washington /
hydro@hydro.washington.edu