Landscaping a large area with Level Streaming / World Composition

I have a virtual environment that’s set in the waters off the coast of Houston, TX.
I’ve used CityEngine to get some textured buildings from satellite data.
Other than painting by hand, how can I get the elevation / 3d geometry for the landmasses?
The area is rather large (a couple square km), so I HAVE to have it broken up into tiles that can be loaded/unloaded by distance.

I have some 2d, top-down satellite map data I can use. I was originally using it as a stencil and making splines on the landscape to “extrude out” the land above the waterline. But spline landscapes don’t seem to go across landscape boundaries into the next tile, so lining them up would be nightmarish or impossible.

There has to be a saner way.
I need some course, 3d geometry of the land. Doesn’t have to be textured or perfect.
Industry software is fine; my organization loves licensing stuff.
What’s the best way to do this, in your opinion?

What I ended up doing:

I downloaded some PNG heightmap files for the area of interest. The tool I used for this was “Heightmapper” Heightmapper URL.

I took the PNG for the total area and brought it into GIMP. I used “Guides” in Gimp at 127x127 intervals (what UE wants for a square landscape tile). I then sliced the image into pieces using those guides.

Using a Powershell command, I renamed the png tiles to be in the correct naming convention for Unreal: “name_X0_Y0”. Replace “name” with whatever, I used “Tile”. Replace “0” with whatever number your tile is on that axis (Top left is X0, Y0), (Bottom right is Xn, Yn), (Top Right is Xn, Y0).

Once the PNG tile images are named correctly (also make sure they’re exactly 127x127 pixels), bring them into Unreal. Make sure you have “World Composition” ticked on in your “World Settings” pane. Go into the “Levels” pane, click “Levels”. There should be an option to “Add from Heightmap” or something like that. Select your tiles, and make sure the “Flip Y” setting is turned off for your import (mine was bringing in tiles rotated incorrectly, and that was why). Adjust your Z-scale during the import; you won’t be able to adjust it later. I used “4” (originally 100+ on mine) and it looks okay.

You can now use the landscape tools to sculpt and paint those tiles. Just make sure the level they’re on is loaded. I was able to sculpt and paint all tiles by loading them all, and making the top left tile level “current”, then highlighting ALL the tile Landscape Streaming things in the heirarchy.

Hope this helps. There’s probably a saner way to do this, but this WORKS.