Glossary for Geospatial Science

extrema points:� The highest and lowest points and flat areas locally as indicated by the elevation raster cell values.� Extrema are change points determined by the comparison of each cell to the eight adjacent cells.� A cell whose eight boundary cells are all lower than the cell is defined as a single local maximum.� A cell whose eight boundary cells are all higher than the cell is defined as a single local minimum.� Two or more adjacent cells with the same value whose boundary cells are all lower are defined as contiguous local maxima.� Two or more adjacent cells with the same value whose boundary cells are all higher are defined as contiguous local minima.� Two or more adjacent cells with the same value whose boundary cells also have the same value are defined as a flat area.