jarvist
New member
We (Imperial College CC) are hoping to finally re tie-in the surveys of the caves on our summer expo to a central GPS location. Does anyone have any recent experience (post WAAS & the end of SA) with improving the accuracy of GPS fixes by averaging, and estimates of potential error?
Our current plan is to define a PSS / trig-point on the surface near the cave systems with a good view of the sky, setup our cheap garmin eTrex on a tripod above this point & data-log WAAS/EGNOS GPS locations to a connected laptop once a second.
Currently we don't seem to be able to get DOP (dilution of precision) data to be logged.
Does anyone have any suggestions for methods of discarding or weighting low-quality data, either through knowledge of the predicted DOP or by sampling the scatter in measured signals by time?
I also understand that further increased accuracy can be achieved by post-processing the data + including information from survey ground stations, such as the UK Ordinance Survey RINEX network - does anyone have any experience with this?
I also understand that due to the main ionospheric nature of the GPS signal degradation, that readings are most stable during the night - is it worth staying up late to get a better fix?
That said, considering that a single WAAS/EGNOS fix now has an accuracy of <3m, perhaps any higher accuracy is unnecessary when compared to survey errors and the rate of spread of tectonic plates!
Our current plan is to define a PSS / trig-point on the surface near the cave systems with a good view of the sky, setup our cheap garmin eTrex on a tripod above this point & data-log WAAS/EGNOS GPS locations to a connected laptop once a second.
Currently we don't seem to be able to get DOP (dilution of precision) data to be logged.
Does anyone have any suggestions for methods of discarding or weighting low-quality data, either through knowledge of the predicted DOP or by sampling the scatter in measured signals by time?
I also understand that further increased accuracy can be achieved by post-processing the data + including information from survey ground stations, such as the UK Ordinance Survey RINEX network - does anyone have any experience with this?
I also understand that due to the main ionospheric nature of the GPS signal degradation, that readings are most stable during the night - is it worth staying up late to get a better fix?
That said, considering that a single WAAS/EGNOS fix now has an accuracy of <3m, perhaps any higher accuracy is unnecessary when compared to survey errors and the rate of spread of tectonic plates!