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leroy10
March 4th, 2010, 03:33
Hi All,
Found an interesting link that could be useful. Not sure if there's a conversion path from the formats on offer to FS but worth a mention just in case.

http://rimmer.ngdc.noaa.gov/mgg/coast/getcoast.html

Cheers :ernae:
Lindsay

SdC Redux
March 5th, 2010, 02:35
Hey that's cool. Let's see how it compares to using SHP files of WaterBody data

rhumbaflappy
March 5th, 2010, 05:54
These files are a much less detailed than the SWBD masks. But the hi-res US masks should be OK.

There are also GSHHS files available. Their problem is they are offset about 200 meters to the west! Their documentation even acknowledges this, but they don't want to correct it. And that mislocation isn't always the same.

The SWBD masks also can have problems. They are 'sawtoothed' and sometimes have errors related to cloudcover in the LandSat7 images that were used to make the files. Basically, the masks were drawn on Satellite images, then a raster to vector process made them polygons. For smaller areas we can get better results by drawing vectors in SBuilderX! But for LOD5 areas, this becomes a 'labor of love'.

Sawtoothed shapefiles can be smoothed. There's an interesting website called MapShaper that can do this:

http://mapshaper.com/test/demo.html

Dick

rhumbaflappy
March 5th, 2010, 12:16
This link explains the saw-toothed effect of the SWBD masks, what smoothing does, and why commercial, or hand-drawn vectors would be better.

http://www.scenerysolutions.com/doc/SRTMData.pdf

Dick