Why were the passive station coordinates changed in December 2002?
A. Coordinates of ALL the passive stations were updated following a complete readjustment of the entire network. This new adjustment is known as OSGPS2002. OSGPS2002 incorporates many extra observations and also extends the passive network into the Scottish Islands, the Scilly Isles and the Isle of Man. The expected coordinate errors at a passive station are now improved to 0.055 m horizontal (95%) and 0.066 m vertical (95%). Hundreds of observations between passive and active stations have been included in OSGPS2002 meaning that the two networks are now in closer sympathy. The rmse East, North and Up residuals between OSGPS2002 and the previous adjustment are respectively 0.0208 m, 0.0118 m and 0.0416 m. These changes are due to the improvements in the network through the extra observations and also due to the change in definition of EtrS89 via the fixed control. For the previous adjustment ETRS89 was defined by fixing the 26 EUREF GB 92 (also known as SciNet92) stations around the co
