GPS coordinates do not map to the cartesian corrdinate system used in ThreeJS. They are completely different.
To position threejs assets referenced with real world, you’ll need more than GPS. Consumer GPS have precision errors (~5 m) which render it unviable for the level of precision you may need to position objects on a room scale. Most AR solutions use photogrammetry and/or more complicated systems to position virtual objects in space. This can be pretty challenging to build on your own and stacks like ARKit, WebXR, ARCore etc. try to make this easier for developers to build on top of.
Following links might help with your search:
https://stemkoski.github.io/AR-Examples/