GEOG281 Lecture Notes - Lecture 7: United States Geological Survey, Thematic Mapper, Level Of Measurement

• School: University of Waterloo
• Department: Geography and Environmental Management
• Course: GEOG281
• Professor: Su Yin Tan

Document Summary

The raster model divides the geographic area into a regular grid of cells in speciic sequence. Convenional sequence is row by row from the top let corner. Space-illing every locaion corresponds to a cell in the raster. Regular tessellaion (division of space) that can be conceptualised as a matrix- like series of cells. Grid origin usually cell in upper let corner. Grid resoluion minimum linear dimension of the smallest unit of geographic space sampled. Atributes are explicit: oten only a single atribute is assigned to a cell, otherwise, a key" ideniier in each cell links to related database iles containing muliple atributes for each grid cell. Raster models do not provide explicit locaional informaion. Raster orientaion angle between real world north and north direcion deined by raster columns. Choose raster cell size 1/2 the length (1/4 the area) of smallest feature to map. Set data type (integer, real: overlay grid over study area.