Political Border and Coastline Files
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FreeFlyer includes the following political border and coastline data files:
The data source for the coastlines and political borders is the Global Self-consistent Hierarchical High-resolution Geography (GSHHG), Version 2.3.5 April 12, 2016. The GSHHG includes the World Vector Shorelines (WVS) and the CIA World Data Bank II (WDBII).
The political borders can be visualized using LineLayers on a CelestialObject Globe. The coastlines and coastline offsets can be visualized using BoundaryLayers on a CelestialObject Globe. See the Globe Layers page of the Generating Output guide for more information and syntax examples.
Line Layer File Format
The borders_global_countries.dat and borders_US_states.dat files use the LineLayer binary data file format described below:
Boundary Layer File Format
All of the coastline files use the boundary layer file format. BoundaryLayers are configured using specialized image files called B-spline-interpolated Signed Distance Fields. These grayscale images are encoded with information that allows FreeFlyer to render the coastlines and up to 10 coastline offset borders very quickly. The level of detail that you will see in the coastlines depends on the resolution of the boundary layer file you select. The grayscale value of each point in the image represents the Vincenty distance (across the surface of the WGS 84 ellipsoid) in kilometers from the location of the center of that pixel to the nearest land/water boundary.
All the coastline boundary layer files delivered with FreeFlyer use the 0.9 grayscale value as the coastline boundary value, and the maximum coastline offset border distance that can be rendered is 500 km. The boundary layers delivered with FreeFlyer include coastline data for all land masses together, US coastlines only, and non-US coastlines only. Using the separate US and non-US coastlines allow you to use different colors/styles and different coastline offset distances for the US and non-US land areas, which can be useful depending on mission-specific constraints. This is demonstrated in the EntryFootprintWithCoastlineOffsets sample Mission Plan within Generating Output.
Please contact FreeFlyer technical support if you are interested in other custom boundary layers.