National Ecological Framework (20 of 23)
GRASS (raster-based GIS program)
GRASS is a public domain raster based GIS, vector GIS, image processing system, graphics production system, and spatial modeling system.
Name: s.surf.idw - Surface generation from sites data program
Synopsis: s.surf.idw input =name output =name [ npoints = count ]
s.surf.idw fills a raster matrix with interpolated values generated from a set of irregularly spaced data points using numerical approximation (weighted averaging) techniques. The interpolated value of a cell is determined by values of nearby data points and the distance of the cell from those input points. In comparison with other methods, numerical approximations allows representation of more complex surfaces (particularly those with anomalous features), restricts the spatial influence of any errors, and generates the interpolated surface from the data points. It is the most appropriate method to apply to most spatial data. This program allows the user to use a GRASS site list file, rather than a raster map layer, as input. The program will be run non-interactively if the user specifies the values of needed program parameters and any desired optional parameter values on the command line, using the form.
The Center for Spatial Research (CSR) is an interdisciplinary lab, which is dedicated to research using spatial analysis. The research team at CSR currently supports several research programs including the development and support of GRASS GIS, spatial modeling and analysis, and hydrology and water resources research (http://www.baylor.edu/csr/).