Determination of the geographical co-ordinates
The geographical co-ordinates of the astronomical observatory “G. Colombo” of the Gruppo Astrofili di Padova are determined in a very precise manner utilising a GPS receiver connected to a computer and a particular post-processing software.
The antenna of the GPS receiver was set exactly on the vertical of the telescope and recorded for two hours the pseudoranges, i.e. the uncorrected distances, for atmospheric effects, of the GPS satellites were visible in that period.
Following this, with an appropriate programme we performed the calculation: that is comparing the pseudoranges recorded by our GPS receiver with those recordings, in the same period, by another close station for which we know the exact geographical co-ordinates. In this case we used the recorded data from the station of the University of Padua (a member of the EUREF Permanent Network) that is only 800 metres away. We also utilised the ephemeredes of the GPS satellites derived from observations at the terrestrial stations. These ephemeredes are precise within a few centimetres and it is possible to find them on the IGS site.
The processing of the data produced the following results:
Latitude:
N45° 24’ 14.89” ±0,03” rms
Longitude:
E11° 53’ 37.18” ±0,02” rms
Elevation a.s.l.:
24.9m
The height above sea level, instead, was calculated directly measuring the distance (12.4m) of the declination axis of the telescope in respect of the road level: the height of which (12.5m) was found on sheet No. 119 of the aerophotogram-metrical relief of 1996 of the Padua Council.
2005 Gruppo Astrofili di Padova ©