In the process of creating a floor plan in the PLNAR Pro App, you expect measurements to stay in their original place, but that is not always the case. Occasionally, users notice something called "drift" where their points are moved across the plane without direction.
If you have already created your room's perimeter, this may not be an issue as your measurements are locked in place & will remain unchanged. However, drift can be an issue if you are looking to take measurements within the room or draw additional features.
Flat surfaces without texture
Spaces with dim lighting
Transparent or reflective surfaces
Now, you are not helpless against drift. Here are a few drift reducing tips:
Place an object in view to add texture, like a piece of paper or your foot
Increase the lighting in the room by opening windows, turn on lights, turning on your phone flashlight, or bringing additional lighting
Have a clear starting point. Place your first point in a spot avoid of glass and other reflective surfaces before mapping the more difficult corners.
Remain stationary, close to the room's center, and begin tracing the room from a distance. Minimal movement helps to establish solid corner points.
Once drift occurs, there are three ways to fix it depending on the severity of the problem.
Recenter the model by returning a corner point you have already placed and move the phone in a circular motion like you were trying to calibrate, make sure to provide good visibility of the floor and the intersection of the walls
Fine tuning your model, for help check out this article about How to Fine Tune.
Start a new room by pressing the icon indicated in the photo below which is located in the top right of the capture screen
Other reasons for drift include dynamic or moving surfaces and extremely bright spaces, but those are not as common while building AR rooms within houses.