World Pictures

[selden]

What does that histogram analysis look like on an Earth-derived heightmap?

I don't know.

Can you provide a pointer to one that I can try? A quick Google search turned up ways to get heightmaps of regions (e.g. http://www.tt-forums.net/viewtopic.php?f=29&t=27052 ) but I haven't found a complete one yet.

Whilst it looks bad on the histo, it is supposed to be a 16 bit PNG so its a smallish section of 65K levels instead of 256.

That's one of the problems that I realized when I woke up this morning. I guess I'm going to have to write my own utilities to do the kinds of manipulations I want to do to the height values.

Do you know what scale factor was used when the translation was done between the altitude and the 64K binary values?

I'm guessing that the large spike is due to the coastal regions of the continental shelves, so presumably is near 0.

[waldronate]

I don't know.
Can you provide a pointer to one that I can try? A quick Google search turned up ways to get heightmaps of regions (e.g. http://www.tt-forums.net/viewtopic.php?f=29&t=27052 ) but I haven't found a complete one yet.

I don't have a link to a good PNG heightmap, but I used Wilbur to read the ETOPO2 data and write out an equal-area 8-bit heightmap based on that data set. The histograms for each area shown below. The hump to the left is the oceanic abyssal plain and the big spike is the coastal plain/continental shelf. A straight histogram on the Plate Caree projection of the original ETOPO2 data set has some artifacts as shown in the second one (that hump off to the right in the plate caree projection is due to polar distortion for Antarctica, most likely).