Yes Kaaiinn,
that is correct though difference between the 2 measurements (using sparse cloud or dense cloud) seems to be small....
In example, i have 2 markers (1 and 2) on a photo (Drohne01634) and I print out their image coordinates, world coordinates and distance between the 2 using first point_cloud (sparse cloud) as surface and then dense_cloud. Difference is at cm or mm level....
For 2 markers set further apart on same photo, the difference in distance between using sparse or dense cloud is still small (2cm). See 2nd attachment...
Another example where distance calculated using 3dModel as surface vs point cloud shows much more discrepancy around 55 cm...3rd attachmant
Last example shows 2 measured distances using projection of points on 2 surfaces :
- point-cloud represented by red line;
- 3D model represented by brown line.
It is clear that 3D Model distance is much more precicse as projection on a closed model really represents the position of 2 points on surface while projecting onto the sparse cloud will only pick the closest tie point to actual projection as seen in right window where red line vertex near point 5 (roof corner) can only pick a tpt a liile inside the roof, thus leading to less accuracy using point_cloud as surface....