Due to the relatively low flying height we were able to generate a
DSM at 2 cm resolution and an orthomosaic at 1 cm.
An assessment of the geometric accuracy in easting (X), northing
(Y), and height (Z) was carried out for the orthomosaic and DSM.
Thirty of the small orange GCPs (excluded from georeferencing in
the SfM process) were identified in the orthomosaic. The coordinates of the disk centroids were retrieved from the image mosaic
and compared to the corresponding surveyed GPS coordinates,
resulting in mean and root mean squared error (RMSE) accuracy
measures in the X and Y direction. The height value was derived
from the DSM for the GCP centroids and also compared to the GPS
observations, producing mean and RMSE accuracy measures for the
Z direction (Höhle and Höhle, 2009; Harwin and Lucieer, 2012