What is the sea level on Mars after full terraforming?

[SievertChaser]

Just wondering to avoid the dissonance of my colony being shown as underwater.

[Ericus1]

Unfortunately, planetary water levels are not reflected on the colony map. Would have added a nice degree of dynamic play, but that is abstracted away. No underwater colonies.

[SievertChaser]

No, I just mean where the water eventually reaches on the global map, in meters. A lot of the easier colony sites seem to be in the northern hemisphere, which is the bottom of Mars's ancient megaocean.

[Ericus1]

It tells you on the colony selection screen. If your colony's average altitude is negative, it'll be below the eventual ocean.

[SievertChaser]

You see, that's where I'm worried. There was such a value there long before Green Planet. And the Martian datum ("sea level") is defined pretty damned arbitrarily. Eyeballing from Olympus Mons and Hellas Planitia, the height in the game is just that reference height from current maps of Mars.

Now, I'm pretty sure that they still use the datum as sea level (which is a widespread but huge assumption among people who draw maps of a terraformed Mars), but I wouldn't mind if someone were nerdy enough to check.

[Ericus1]

If you just sit on the intro screen long enough with the GP DLC enabled, it shows the planet getting terraformed and the approximate area that will be underwater. And literally, if the altitude value is negative it's going to be underwater.

https://assets.rockpapershotgun.com/images/2019/05/planetary.jpg

[SievertChaser]

Originally posted by Ericus1:

If you just sit on the intro screen long enough with the GP DLC enabled, it shows the planet getting terraformed and the approximate area that will be underwater. And literally, if the altitude value is negative it's going to be underwater.

https://assets.rockpapershotgun.com/images/2019/05/planetary.jpg

Yeah, but the part that's visible in the main menu is Vallis Marineris, which is a whopping -3500 m surrounded by areas 3500 m above datum, so it wasn't good enough for precise measurements.

The screenshots I found didn't quite align with each other or 3rd-party maps... plus, and I think it's visible in the screenshots you posted, at least some versions of the game would forcibly "unflood" areas around each base, about twice the width of the icon. Recreating your screenshot, the US colony is on Arabia Terra, at -1700.

Anyway, I found a decent area around southern Elysium that I'm going to stick with for now.

[Ericus1]

The game does do that on the planetary map view, where any colonies, including rival colonies, will show with a very small land area around their symbol.

[lost]

Presumably part of the terraforming process happening behind the scenes is building a network of dams or sea walls to keep back the ocean. All of which would occur outside the colony map.