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Combine GeoGraphics to see US borders on ReliefMap

Posted 9 years ago

I am trying to produce a GeoGraphic showing the horizon view from a rocket at the edge of space. On top of the horizon I am trying to overlay the outline of state and province boundaries to provide some reference.

The horizon view I am looking for is a circular shaped relief map of the visible horizon. Using the following code I am able to produce the horizon view I am looking for except it is missing the state boundaries:

horizon = GeoGraphics[{GeoStyling["ReliefMap"], EdgeForm[Black], 
GeoVisibleRegion[{44.0519, -123.0867,  Quantity[100, "Kilometers"]}]}, 
GeoBackground -> None]

I am able to produce the outline of the state boundaries I desire and my horizon view, but I am unable to remove, or cut away, the unnecessary geography with this code:

states={I am using the administrative entity value for the western states};

 {GeoStyling["ReliefMap"], EdgeForm[Black], Polygon[states], 
  GeoVisibleRegionBoundary[{44.0519, -123.0867, 
    Quantity[100, "Kilometers"]}]}]

An altternate attempt:

GeoGraphics[{GeoStyling["ReliefMap"], EdgeForm[Black],
  GeoVisibleRegion[{44.0519, -123.0867, Quantity[100, "Kilometers"]}],
  EdgeForm[Black], Polygon[states] }, GeoBackground -> None ]

Any suggestions?

POSTED BY: Jon Rogers
3 Replies

Try this:

visible = GeoVisibleRegion[{44.0519, -123.0867, Quantity[100, "Kilometers"]}];

states = GeoEntities[visible, "AdministrativeDivision1"];

geographics = GeoGraphics[{EdgeForm[Black], FaceForm[], Polygon[states]}, 
GeoBackground -> "ReliefMap", GeoRange -> visible, GeoProjection -> "Equirectangular"];

image = Rasterize[First[geographics], "Image", RasterSize -> 1000];

GeoGraphics[{GeoStyling[{"GeoImage", image}], EdgeForm[Black], visible}, GeoBackground -> None]

enter image description here

The basic idea is using GeoGraphics twice. This basically allows you to put any part of a map inside any geo polygon of another map.

The first GeoGraphics produces a rectangular map (in lat-lon coordinates; note the use of GeoProjection->"Equirectangular") with the exact lat-lon ranges corresponding to the region your are interested in (note the use of GeoRange->visible). The result is given as a GeoGraphics[Graphics[...], ...] object. We take the Graphics[...] and rasterize it as an Image with enough resolution.

Finally, with the second GeoGraphics, we take the resulting Image and place it inside the geo visible region using GeoStyling[{"GeoImage", image}]. Note the use of "GeoImage" (instead of the alternative "Image"); this is to project that image to the geo projection chosen by the second GeoGraphics.

If you have questions about the process, do not hesitate to ask.


Posted 9 years ago

Thank you. That was exactly what I was looking for. I am going to have to reverse engineer your code to fully understand how to repeat this in the future.

POSTED BY: Jon Rogers
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