This is getting very close to actual field survey work and IMO the best app, by a mile, to carry out the scanning part in this kind of setting is Dot3D. It's basically been built for larger-scale capture and reliable loop-closure.

Here's a scan of several km (!) of length all done with Dot3D on an iPad [1]. You can also explore the point cloud on the web.

Also, digging a little deeper, here's a study comparing the accuracy and loop-closure capabilities of several 3D scanning apps. It's spot on. [2]

[1] https://twitter.com/netch87/status/1632392369143435264

[2] https://rafaels-blog.weebly.com/blog/why-loop-closure-is-cru...