TIN stands for 'Triangulated Irregular Network' and DEM stands for 'Digital Elevation Model'. Both surfaces represent landforms based on elevation data, and both can be used to show slope, aspect, and contours. A major difference between the two is the file type - a TIN surface is vector based whereas a DEM is raster based.
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| Detail view of a TIN surface, showing contours, nodes, and edges. |
A bonus to a TIN surface is that aspect, contours, and slope can all be depicted and stored within the same file. A DEM raster cannot do this - different files would need to be created to show slope, aspect, and contours... and this could potentially involve multiple steps (for example, a slope raster may need to be converted to polygons if one wanted to show it as vector data).
Another bonus to a TIN surface is that breaklines (essentially, a linear feature) can be used to modify the original topography. This is not possible with a DEM, thus making the TIN surface ideal for engineering applications... or detailed archaeological site maps.
Why aren't we using more TIN surfaces if they're so great? Well, they require a lot of computer memory, and therefore shouldn't be larger than 1,000,000 nodes. That may sound like a lot, but these things tend to be quite detailed and so can reach that threshold easily. TINs also are not the best surfaces to use when one wants to model continuous data over large areas - that is where DEMs shine.
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