This survey has explained a number of concepts on terrains, and some algorithms for various computations. The emphasis has been on TIN algorithms, because the TIN model for terrains is more elegant than the grid and contour line models. A common argument to use grids is the simplicity of the algorithms. However, the current trends in GIS research and in the field of computational geometry have shown that algorithms on TINS need not be . either. More programming effort is required, but this need not outweigh the advantages that TINS have to offer. We won't repeat arguments in the raster-vector debate; a summary of algorithmic methods and specific algorithms for TINS is useful in any case. The search for efficient algorithms on terrains is an interesting area of research where the GIS developers, GIS researchers, and computational geometers can work together to develop a variety of elegant and efficient solutions to practical problems on terrains. The analysis of efficiency of these solutions should be based on realistic assumptions on terrains.