I have dGPS positions collected using a Leica 1200 system (base station and rover) recorded at the same site on multiple occasions over two years (being used to georeference terrestrial laser scanner data).
The positions were collected and post processed in WGS84 and converted to OSGB36 using OSTN15/OSGM15 as if they were ETRS89 using Grid InQuest.
As I understand it, OSTN15/OSGM15 should take ETRS89 lat/long as input and ETRS89 coordinates are slowly diverging from WGS84 coordinates.
Questions: 1) Will my positions be accurate relative to eachother, i.e. if I had surveyed the same mark each time, would the easting, northing and ODN elevation be the same or would it gradually shift due to tectonic plate movement? (I am interested in cm scale changes so the 2.5 cm annual change would affect me)
2) If not, can I correct them using a time dependent transformation?
3) Although I understand any transformation will introduce error, will any offset introduced by OSTN be consistent at a particular position?