Comparison - EVS, PGS, WVS and SRTM (1) Shorelines
Comparison of EVS, PGS, WVS and SRTM (1)Shorelines
A picture is worth a thousand words. The above image contains a small segment of Eiao Island FP. The scale is 1:12,000. What are visually displayed are the shorelines of various global shorelines (PGS, WVS and SRTM (1)) as they compare to my own EVS shoreline. They all fall short of depicting the actual shoreline and that is to be expected. A shoreline is a dynamic geologic entity. It is constantly in motion. There will never be a penultimate map (a static entity) that depicts a global (dynamic) shoreline. With that said, which of the four shorelines works best for your needs. All four shorelines have their uses.
The World Vector Shoreline, "old reliable", works for most mapping needs at a scale of 1:250000 or above. When you work above 1:2000000, the map becomes too busy. But between those two scales, WVS works fine.
Prototype Global Shoreline, when completed, will be "THE" map file for work from 1:62,500 up to 1:1,000,000 scale. It will provide details that will make WVS look like a clunky jalopy compared to a sleek race car. PGS will impact every country in the world. It will require a country-by-country acceptance. It will cause nations to redefine maritime limits and that is not an easy notion for nations to agree upon. Nations will gain or lose valuable real estate because maritime base lines and economic zones will be shifted because PGS shorelines will shift. If the shift results in a lose of real estate, my suspicion is the losing nation will not buy the new boundary. What an exciting proposition for the global community. Much of the above comes from a source within NGA that has the enviable task of completing this monumental map file.
SRTM (1)(SWBD) shoreline was added to show how far this vector mapping program has advanced. It is a solid vector map file that improves mightily upon WVS, but it does not accomplish the precision that is found in PGS. However, again from my source in NGA, there is a more precise global data source within SRTM. It is SRTM Level-2. It is available for the US today, but NGA has access to global coverage at the level-2 precision. I am purposely vague on SRTM Level-2 as I have not done much work with it, but I am certain it will perhaps rival PGS when released to the eager public.
Finally, my own Enhanced Vector Shorelines effort and how it compares with the other three shorelines. I like to think that EVS is the most accurate of the four, but that isn't quite so. The three are global in scope and mine covers islands and some shorelines. The places I have mapped at EVS resolution are more exact in depicting the actual shoreline than any of the other three shoreline sources. My ultimate goals with EVS is to see all shorelines mapped at that level of precision, to develop a consistent decision-making process as to map or not to map certain features and to bump this effort up into a legitimate concerted, well-funded effort that will result in a timely completion of the project within 2 to 3 years.
EVS, in my opinion, is the ultimate map file that can be extracted from Landsat-7 ETM+ 2000 imagery. When 1-meter resolution imagery is released and the coverage is global, the new and improved ultimate map could be created, EEVS (Extremely Enhanced Vector Shorelines). Until then, I will keep myself busy working on my labors of love – creating shoreline maps of islands.
Enjoy!
