Working with Raster Data - Desktop GIS: Mapping the Planet with Open Source Tools - page 68

Figure 4.7: Grid of silver values in pseudocolor

Range 3.9615553319

Mean 0.3253868880

Sum of Squares 991.8232408759

Standard Deviation 0.4478514579

Sum of All Cells 1609.3635482636

Cell Count 4946

This tells us the minimum and maximum values in the grid, the num-
ber of cells, the range, and some other statistics. This is probably a bet-
ter way to get a quick overview of the distribution of a grid, as opposed
to randomly identifying cells.

To make the display a bit more dramatic, we can open the raster prop-
erties dialog box and change the color map from grayscale to pseudo-
color. When we apply this change, we get the result shown in Figure 4.7 .
Now the high value areas are red and the low values are blue, making
it even easier to visually analyze the distribution of the values.

We could take our analysis further by using GRASS to create a con-
tour map of the cell values or by generating a hillshade to enhance the
appearance of the map.