Format for 24 km (1/16’th Bedient) ASCII file containing daily Northern Hemisphere snow and ice coverage produced by the NOAA/NESDIS Interactive Multisensor Snow and Ice Mapping System (IMS)


Each data file contains 30 lines of header information (ASCII text) about the specific data file, followed by a Polar Stereographic 1024 x 1024 array (for the 24 km files) of format I1 (single integer) data, with (1,1) starting at the lower left corner. The top of the file is South America, the left side is the Pacific Ocean, the right side is Africa, and the bottom is Indonesia. Data values in the files range from 0 to 4:


0 – Outside Northern Hemisphere

1 – Sea

2 – Land

3 – Sea ice

4 – Snow


There should be no missing values over the mapped hemisphere.


The 1024 x 1024 Polar Stereographic grid has a mesh length of 23.8125 km at 60 degrees N latitude and is oriented at 80 degrees W longitude.  The coordinates of the North Pole are (513,512).  Grid point (1,1) is at 20.773 S latitude, 125.056 W longitude.