1: the checkbox left to a marker (to left for "long,lat,alt,accuracy,error"...) - does it enable/disable a given GCP for processing ?
2: if there is a marker, (GCP) , but it is not placed in any photo ( "it's icon is not green, but grey") does it have any influence on the processing ?
3: is it possible to have a marker only be used for altitude only ? (aka - the position is +/- 10meters, but we know that flat area had a given altitude of xx.xxx meters)
4: imagine all photos for a map contain ellipsoid (GPS) altitude, then we add some GCP's with local geoid corrected altitude, - is the result expected to be "good" ? - or does all altitudes, (in exif too) - need to be geoide corrected ?