Mars

Titan

Vesta

I discussed this with SpaceEngineer already, but he seemed to think that having some surface liquid was better than having none, and since the diffmap was used as a height map the result was seas in the tropics. I agree with you that they should be removed.

The distribution of color on Vesta is procedural since there isn't a good, publicly available complete global color map for the planet. The color scheme for the world as a whole however is accurate, based on the best available color data.

There is plenty of room for liquids on Titan - In those areas where they really exist!

Even procedural color generation can be controlled. On Vesta this should just include tones of grey, definitely no brown.

But there is no way to get that information into SE. There is no global topographic map for Titan, which is required, and anyway it will always fill all places up to a certain elevation with liquid regardless of whether it's really there or not. There's no way to use SE's pseudo-3D water on a planet otherwise. It's easy to say "put this there", but actually making that happen is usually extremely difficult if not impossible.

Yes it should. As I said, the colors there match the real colors of Vesta, as sampled from a published true-color map of the planet, which also match well with this image processed by Bjorn Jonsson.

I'd therefore suggest to create an artistically inspired elevation map

Nevertheless, certain, low-lying areas, e.g. Feralia Planitia, appear unnaturally brown in Space Engine.

Like I said, this is easy to say, but difficult to do. You're welcome to try it yourself if you want.

Again, as I said, it's procedural, so it's not going to be accurate. I was just refuting what I perceived to be a claim that there is no brown on Vesta, just gray. You can try changing the order that the colors are specified in Vesta's entry in the asteroid catalog to get different results if you want, but it's never going to be realistic.

Other procedurally generated asteroid surfaces do not appear with such brown regions.

it has already been done for other bodies in the Sol system.

I thought Space Engine was a closed source project

Not to the extent that it would be necessary for Titan.

Io, for instance, seems to feature a global elevation map, which was handcrafted (?) to emphasize landforms seen on the real Galileo/Voyager mosaic.

The Io elevation map is just a grayscale copy of the color/albedo map, the same as Titan. All Galilean moons use this method, or a variation of it.

Based on your experience, could such an "improved" product be forwarded to the developer in order to be incorporated into the program, or would it stay an optional add-on?

If someone were to make such a product, and if it were of sufficient quality, then yes it he would incorporate it into the default distribution.

Mars

Titan

Vesta

Io, for instance, seems to feature a global elevation map, which was handcrafted (?) to emphasize landforms seen on the real Galileo/Voyager mosaic. I am not sure I understand what the difference between the artistic topo-maps for the Galilean moons vs. Titan would be. Nevertheless, I do acknowledge, that creating such a map is probably time consuming. Were the current ones for Io and co. done by the community or by the developer?

In this case it is best to wait for the upcoming (next few weeks/months) release of a new global VIMS map of Titan, including new images taken around the north pole, and use this as a baseline for any modified/improved map.

For Titan, using the radar reflectance map as an elevation map gives the result you are seen in SE 0.972.