EVS-Islands

PGS Overlay on Suwarrow Atoll

One of the readers of EVS-Islands suggested that I look into an improved WVS (World Vector Shorelines) file. I am aware of something called WVS Plus, and as yet have not bothered to download it. This was supposed to be much better. Rumor is, this is a world shoreline vector file(s) extracted from Landsat-7 imagery. I thought, "Hell, that is what I am trying to do? This file is going to make my efforts of no consequence.

Well, the file exists! And it is available at the Prototype Global Shoreline Data (PGS) page. The files are easily downloaded. They are in .shp file format. They are zipped and ready to load into your mapping software. Global Mapper loads them and they can remain zipped. They are very large files unzipped (average between 10 to 100-mb per file with a total of 28 files).

After a preliminary look, I can confidently state that PGS is a major improvement over WVS. At 1:250,000, PGS shows a different shoreline than WVS shorelines. At larger scales (1:25,000) they show a shoreline that is very close to Landsat-7 imagery, whereas WVS is clunky and coarse.

To compensate for cloud cover, the method EarthSat employed was to leave the area blank (no vectors). I am sure NGA and EarthSat already have a solution in the works to approximate cloud covered shorelines.

Now my question, "Is EVS necessary? Is this shoreline what EVS strives to be? No! I still have a mission. Their shorelines are just that - shorelines. They used a land masking method that appears to not include human eyes. There are irregularities, not as irregular as WVS, but misalignments. My EVS efforts of islands and shorelines correct most of these irregularities.

The final process EarthSat and NGA should consider is "human eyes" to confirm what software solutions have suggested. If that is to be done, great! If not, then my quest remains - Enhanced Vector Shorelines for the World!

Posted by Mr Minton on Tuesday, June 13, 2006 at 6/13/2006 08:29:00 AM | Permalink