Is scale constraint mandatory?

Hi!

I have made photogrammetric models with a Mavic 3E drone without GCPs. Before taking photos, I have taken manual measurements from the area. When I have checked these measurements from point cloud in pix4d mapper, I have found that the differences in relative accuracy are usually about 0.5%, or even less.

This is usually completely sufficient accuracy for my needs, so my question is:

Do I need to create a scale constraint in the point cloud or is checking the manual measurement(s) from the point cloud enough to verify the relative accuracy, as the point cloud is automatically scaled, when the pictures have GPS information?

If the manual measurements are measured from the point cloud and they are accurate enough (max 0.5% error), does the scale constraint provide any additional value for my point clouds relative accuracy?

And I’m only interrested about the relative accuracy not absolute accuracy.

Best regards

Sami