Geo-region data for countries/states/oceans

I'm developing an application where entities are located at positions on Earth. I want to have a set of data from which I can determine what region(s) a point is contained within.

Regions may be of types:

• Continent
• Country
• Lake
• Sea
• DMZ
• Desert
• Ice Shelf

...and so forth.

I'm envisioning representing each region as a polygon. For any given point, I would test to see if it is contained in each polygon. Alternative ideas are very welcome.

I am also hoping to find public domain data sets that contain some or all of these boundaries.

Some of these polygons are going to be enormously detailed (possibly more detailed than I need) and so I need tips on performing these calculations efficiently. Methods for simplifying 2D polygons would also be useful I expect. What are the best pract开发者_开发问答ices for these kinds of things?

Can anyone recommend any good resources of this data, any particular programming approaches or existing software libraries that do this kind of thing?

EDIT

I should point out that the data set of regions will be fairly static, so precomputation is a good option if it improves performance.

If you're on a plane, the common algorithm is to draw a random straight half line from your point and checking for the number of intersections points with the given polygon. If it is odd, you're inside, if it is even, you're outside. You have to beware of vertices and of numerical inaccuracies.

Now, you're on a sphere. You can project it on a plane (the actual projection you use can depend on the polygon) and do the above.

A great resource is Natural Earth.

Natural Earth is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data, with Natural Earth you can make a variety of visually pleasing, well-crafted maps with cartography or GIS software.

The data is provided as ESRI Shapefiles. There are many Shapefile libraries in existence.

If you can't find support for Shapefiles in your programming languages, this PDF details the file format.