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I have an application that draws a vector map of the 50 United States. Each state is a polygon. These polygons change color as the state of the application changes.

I obtained the coordinates I'm using now by laboriously tracing a scanned in map with a mouse, recording the screen coordinates as I did so. As you can imagine my vector map is pretty ragged. I'd like improve the appearance of my maps by using real boundary coordinates for each state, and in the future use other political boundaries in my app such as counties or congressional districts.

I know nothing about GIS systems, nothing at all. I do think that given a vector of lat/long pairs for the borders of each political entity I could convert the lat/longs into screen coordinates. I used to be an Air Force navigator, so I'm comfortable with lat/long calculations.

Bottom line: I need an open source or public GIS database system that could spit out a list of Lat/Long pairs for the boundaries of the fifty States.

Can someone provide a pointer to such a database and hopefully a tutorial of some kind describing how to extract political boundary information from it?

Thanks in advance!

Jim In Texas
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1 Answers1

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The Census Bureau provides the TIGER data sets that include shapefiles for state outlines (and much, much, more). The downloads are in ESRI Shapefile format, which can be opened by most GIS applications, such as the easy to use open-source QuantumGIS. To convert the shapefiles to a format that's easier to work with, see this question. Once you've got the vector data into your program, you'll probably realize that it's more detailed than you want. Check gis.stackexchange.com for some tools to simplify the polygon outlines. Once you've got the sets of points you want, you may want to use the PROJ library to handle the projection of the points on to your map.

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user57368
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