How many ground control points (GCPs) are required?

[rese_support]

PARGE is a fully parametric orthorectification solution. Theoretically, it therefore would not require any GCPs. In practice, it appears that the absolute calibration of current INS systems are not yet accurate to a sub-pixel level. For more accurate calibration, a number of at least 3 GCPs per image strip are required. If GCP quality is lower than the spatial resolution, a statistically reasonable amount of GCPs is recommended (i.e. 20-30 GCPs within one flight strip). In the worst case scenario of missing, drifting, or partially corrupted data streams, it is recommended to use 1 GCP per 100 image lines. PARGE offers a wide variety of 'Special' functions which lets you save such ill-posed data.For stable systems, the boresight alignment may be made once per flight campaign and the such derived offset angles may then be transferred to all acquisitions.