EVS-Islands: How To Adjust PGS to EVS Precision

PGS Vectors Along First Shoreline Section

Adjusted PGS Vectors Along First Shoreline Section (EVS Precision)

PGS Vectors Along Second Shoreline Section

Adjusted PGS Vectors Along Second Shoreline Section (EVS Precision)

To make sense out of these 4-images it is best to left click, select "All Sizes" and study the original sized image.

I think the PGS (Prototype Global Shoreline) has the potential to be even better than what it will ultimately become. The algorithm used to generate the vectors used "Short Wave Infra-Red (SWIR) bands which provided the best shoreline delineation and an accuracy of about 50-meters". (See NGA White Paper). Correct! PGS is a major improvement over WVS.

PGS is what I have long discussed as my ambition, "to create an Enhanced Vector Shoreline" map of the world". Using Landsat-7 imagery, I would generate shorelines. And that is exactly what EarthSat has done. They have taken Landsat-7 ETM+ 2000 imagery and generated a Global Shoreline. At first look, it is impressive. Especially when you compare to WVS vectors (See previous post). At second look, it is still impressive. EarthSat has created a world shoreline that NGA makes available at NO COST! At third look, PGS can be better - EVS Precision.

Working with 2-sections of shoreline in Central America, I determined how much adjusting would be required to enhance PGS to an EVS level of precision.

38% of the vectices (49) had to be adjusted. The adjustments were small, a few millimeters, but when completed they transformed a very good shoreline into an excellent shoreline - EVS Precision.

5% (6) of the vectices were deleted. These were deemed,by me, to be unneccessary toward generating a quality product. Parts of the PGS shoreline contain strings of vectices that appear to be a programming anomoly. There are 8 to 10 vertices strung together along a 2-centimeter straight line. So, I deleted the extra vertices to correct the overplots.

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