Really cool, ive been working on the same type of system with the whole world but as a flight simulator, how did you get the costlines or when the water and terrain collide really smooth, And how did you caculate the water height i tryed Y0 and the thinnest size i could but it was not accurate any tips?
For water, I used map tiles where water areas are represented by a specific color. I simply check the RGB values to identify water regions and assign the appropriate materials. For instance, OpenStreetMap tiles mark lakes, rivers, and oceans with the color RGB(170, 211, 223)
This does require an extra HTTP request, but it worked well for me.
As for water depth, I didn’t implement actual depth. Instead, I just placed a layer of sand beneath the water, giving the appearance of a shallow surface.
If you want to add depth, one approach is to calculate the distance from each water pixel to the nearest non-water pixel. This could give you a depth value based on proximity. However, this method is computationally heavy. Using a flood-fill algorithm might optimize it, but I found it unnecessary for my project.
I use voxel terrain, so this might work differently if you’re using meshes or parts.
About voxel terrain, It is roblox terrain, In performance its not efficient (Mostly coding it) if you are gonna use it for large scales, But it is really detailed if you know how to put stuff together with it, Like foilage:
For satellite, I found out that HERE maps has this url to get the satellite imagery. Im not sure if its meant to be free, But i mean its there so might as well use it until they find out.