W Randolph Franklin, Metin Inanc, Zhongyi Xie, Daniel M. Tracy, Barbara Cutler, Marcus V A Andrade, and Franklin Luk. Smugglers and border guards – the GeoStar project at RPI. In 15th ACM International Symposium on Advances in Geographic Information Systems (ACM GIS 2007). Seattle, WA, USA, Nov 2007.
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We present the GeoStar project at RPI, which researches various terrain (i.e., elevation) representations and operations thereon. This work is motivated by the large amounts of hi-res data now available. The purpose of each representation is to lossily compress terrain while maintaining important properties. Our ODETLAP representation generalizes a Laplacian partial differential equation by using two inconsistent equations for each known point in the grid, as well as one equation for each unknown point. The surface is reconstructed from a carefully chosen small set of known points. Our second representation segments the terrain intoa set of regions, each of which is simply described. Our third representation has the most long term potential: scooping, which forms the terrain by emulating surface water erosion. Siting hundreds of observers, such as border guards, so that their viewsheds jointly cover the maximum terrain is our first operation. This process allows both observer and target to be above the local terrain, and the observer to have a finite radius of interest. Planning a path so that a smuggler may get from point A to point B while maximally avoiding the border guards is our second operation. The path metric includes path length, distance traveled uphill,and amount of time visible to a guard. The quality of our representations is determined, not only by their RMS elevation error, but by how accurately they support these operations.

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