
MagicPlan has been out for ages and originally just worked off the camera and the accelerometer to help build a floor plan.

They both now take advantage of the Roomplan API which Apple introduced in iOS and iPadOS 16. MagicPlan and Pol圜am seem to be the most focused on building a schematic level building model which could be imported into other tools if needed. using a gimbal), but ultimately you'll need to do tape or laser measurements and modify the models that these tools can build, or just model it yourself with the scan as a reference. There are techniques to improve accuracy (e.g.

The short answer is that the LIDAR and iOS APIs are remarkably powerful, but not 100% accurate. I found this youtube channel has some pretty good walkthroughs (quite literally) of using various iOS apps to scan architectural spaces.
