imshade

Plot shaded relief, optionally using simulated lighting direction

IMSHADE will plot a matrix representing topography as a 3-component color image, with intensity proportional to the magnitude of the topographic slope of each pixel. Optionally, it can take an argument for lighting angle to use the directional slope.

The current colormap will be used, but future changes in the colormap will not alter the image, since it is now displayed as RGB derived from the colormap and shading.

Nondirectional shading usually scales well, though it is not very robust to spikes in the topographic gradient. The normalization used for directional shading does not always yield satisfactory results and may benefit from some tweaking.

Attached screenshot shows a seamount plotted with IMAGESC (no shaded relief) and with IMSHADE.