Pixel values are obtained through a look-up table that relates
the original source data, 2-byte integers representing elevation
or bathymetry in meters above or below sea-level, to color.
The mapping is designed to emphasize the extreme estimates of
sea-level rise and fall since the mid-Pliocene. The mapping is
made using the following algorithm.
if depth < -5000 then color = 0x00 0x00 0x00
if depth < -4000 then color = 0x00 0x00 0x1F
if depth < -3000 then color = 0x00 0x00 0x3F
if depth < -2000 then color = 0x00 0x00 0x5F
if depth < -1000 then color = 0x00 0x00 0x7F
if depth < -120 then color = 0x00 0x00 0x9F
if depth < 0 then color = 0x00 0x9F 0xFF
if depth < 35 then color = 0x00 0x7F 0x00
if depth < 60 then color = 0x00 0xBF 0x00
if depth < 500 then color = 0x00 0xFF 0x00
if depth < 1000 then color = 0xFF 0xFF 0x00
if depth < 2000 then color = 0xFF 0xDF 0x00
if depth < 3000 then color = 0xFF 0xBF 0x00
if depth < 4000 then color = 0xFF 0x9F 0x00
if depth < 5000 then color = 0xFF 0x7F 0x00
if depth < 6000 then color = 0xFF 0x5F 0x00
if depth < 7000 then color = 0xFF 0x3F 0x00
if depth < 8000 then color = 0xFF 0x1F 0x00
if depth < 32767 then color = 0xFF 0x00 0x00