Importing real-world map data

Greetings all. I'm fairly new to Unity, have done some time with Blender (modelling and basic animation) so am finding the editor fairly comfortable & have completed several tutorials without much difficulty.

I would like to tackle a "student project" of my own (with a view to developing it into a real project over time), involving 3d model of a real location.

I have successfully imported terrain heightmap from terrain.party (I'm impressed by how simple this was) for the area of interest, but I find that the resolution of the terrain.party data is pretty low, i.e. my final map has to be quite small or else it appears crude and blobby. I could live with blobbiness in the heightmap, as this can largely be concealed by artistic application of surface features (so long as they're visually appropriate to the real world region). But the region I want to model is an island -- it involves a lot of shoreline, and a blobby low-res shoreline is a real illusion breaker.

So I'm wondering whether there is a method for importing more high-res data, say from Navionics marine charts or official survey data, extracting the shoreline vector, and ("here a miracle occurs") overlaying it onto my existing terrain as a sea level contour.

I am also curious to learn more about scaling from real world to model world. As I understand it, one Unity unit is intended to be one meter. My map area as DL'd from terrain.party was 28km on a side, but the rez was so low that I had to scale it down 10:1 and create a Unity terrain only 2800m on a side (otherwise I was looking at "marshmallow island"). Is it practical to build the whole model at this 1/10th scale? I don't plan any serious physics -- might use the wave features in the water planes and throw in a couple of wind zones to liven up the vegetation, that's all. It's more for VR tourism than gameplay, so good physics doesn't really matter. Can I live with a scaled-down world if I don't need rigidbodies to interact realistically?

Sorry if any of these questions qualifies as Stupid. I'm just getting started, and of course my grasp on the awesome, dazzling potential of Unity's toolset is far stronger than my grasp on the actual skills and knowledge required to realise that potential

 

If you know blender maybe this tool will help you in your quest
https://github.com/domlysz/BlenderGIS

 

many thanks, that goes on my project list to check out!

 

thanks