GGR278H5 Lecture Notes - Lecture 6: Centroid, Azimuth, Map Algebra
Document Summary
Value of a cell may be an average over the cell, or a total within the cell, or the most common value in the cell. May also be the value found at the cell"s central point. For line, polygon, or three-dimensional features, it is the center of mass (or center of gravity) and may fall inside the feature, as shown below for a triangle, or outside the feature, as shown below for a complex line. For multipoints, polylines of polygons with multiple parts, it is computed using the weighted mean center of all feature parts. The weight for a point feature is 1, for a line feature is its length, and for polygon features it is its area. Assignment based upon data value at a cell"s geometric centre. Excellent in cases where there is little localized variability in attribute. Problem when a minority type assigned to a cell.
