Creating an offline georeferenced 3D world map

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Created Aug ’23

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Hy, for my Masterdegree i need to build a georeferenced 3D world in an iOS app. Thereafter there's some data to add to the map, but i think thats not the hard part.

For now i don't know how to start, because all the data has to be stored offline on an iPad. I found lots of free data on the internet. For example Digital Elevation Models or 2D Mapdata. I need to find a to way build a 3D globe to show the DEM and put an Overlay (Map or satellite) on it. Of course there must not be the whole world stored offline. I would be happy if it works for small countrys, or even a part of a country.

Loading of the GeoTIFF DEM into SceneKit could be a way. I've also tried to use some Engines like Blender or Unity. Both with Cesium. But i can't find a way how to use them with offline data. One way could also be using 3D Tiles. Maybe someone has an idea which tools / ways could help me to start the project.

Thanks in advance

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Answer 1

endecotp OP

Aug ’23

I have a couple of apps that do something like this; you may even have seen them.

If your experience with 3D graphics is limited then using a game engine (i.e. Unity) is likely to be a good choice. If you have specific questions about that (i.e. "I can't find a way how to use them with offline data") then asking on their mailing lists / forums is the thing to do. (My apps don't do that; I'm a do-it-all-myself-from-scratch sort of person, for better or worse.)

One thing to worry about is numerical precision. What is your minimum feature size? Generally GPUs use single-precision floats. When you're modelling the whole world that can get a bit tight. Think about that before you go too far.

Something else to think about is map projections. If you don't care about the polar regions, this isn't too difficult. If it's important that you get Antarctica right then some extra work is needed. If in doubt, I suggest using spherical geocentric 3D coordinates.

DEM data compresses quite well with JXL; gdal may not support that yet though. You could store the whole globe on an iPad, at some medium resolution. More realistically, store the whole globe at low resolution and a few areas that you are interested in at a higher resolution.

Good luck!

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Answer 2

creasedpixels OP

Feb ’24

Hi Martin.

I'm just wondering if you made any further advances with this challenge?

I need to create something similar so, if you could support, that would be amazing.

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