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Land-Sea Mask Available

The land/sea mask has been improved (as of 10/5/96) and now includes ocean boundaries from the World Vector Shoreline (WVS) data set. The boundaries for U.S. Great Lakes and St. Lawrence seaway come from the Political/Ocean (ponet) layer of the Digital Chart of the World (DCW). The boundaries of inland water bodies come from the perennial water bodies and polygon features (double line rivers) of the Drainage Network (dnnet) layer of the DCW. The land/sea mask has been generalized during the process of rasterizing the vector data to 1-km grid cells. A 1-km cell is assigned to land or water based on the dominant area of a cell. World Vector Shoreline boundaries have precedence over DCW.

The land/sea mask values are:

0

Land

1

water

2

interrupted area

A NEW shorelines mask is also provided. The shorelines mask was produced from the World Vector Shoreline and the Digital Chart of the World data layers used in the land/sea mask. A shoreline is defined as any 1-km cell that is intersected by a vector that defined the boundary between land and water.

The shorelines mask values are:

0

no data

2

interrupted area

4

WVS shorelines

5

DCW shorelines

Both files are 8-bit raster images in the interrupted Goodes homolosine map projection. The image size is 17347 lines by 40031 samples. The map projection information is provided in an associated document.

The Land-Sea Mask can be compressed with the GNU gzip compression software program before it is delivered.

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