Comments on EVS-Islands: Comparison - NGA PGS to EVS Precision Vectors

Can you provide downloads to vector versions of yo...

2009-05-03T12:19:00.000-07:00

Can you provide downloads to vector versions of your images, specifically see http://en.wikipedia.org/wiki/Wikipedia:GL/MAP#Pitcairn_Islands

Anon, Thanks for your observations. In rereading...

2009-04-19T22:40:00.000-07:00

Anon,

Thanks for your observations. In rereading the NGA PGS Whitepaper (at their website), their vectors approximate the High Water Line. Further into their explanation, they intend their shorelines to be used at scales 1:75,000 and smaller. They admit that the accuracy of shoreline derived from Short-Wave Infra-Red bands is 50-meters (RMS). Another admission "Because the shoreline was primarily computer generated, it is not the smooth line you find on charts and it also contains many short segments." I believe this ever-improving vector defined shoreline is the best global shoreline available. However, I would rather digitize my island shorelines instead of using the rough NGA PGS shorelines.

At the scales my maps are viewed and used (typically between 1:100,000 to 1:25,000) and considering the resolution limitations of Landsat ETM+ (14.5 Meters per pixel), my monoplotted maps provide a reasonably accurate picture of the islands I have digitized using Landsat ETM+ as my base imagery.

How's life at ESRI?

That's some assumption you are making there. How d...

2009-04-19T21:35:00.000-07:00

That's some assumption you are making there. How do you know the imagery you are using are made when the sea level was at, well... sea level? Or that it was rectified based on a sufficiently correct terrain model?
I don't think you can base any kind of accuracy measurement from data that comes from monoplotting. Especially considering the type of data you are using.