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User Name Thread Name Subject Posted
Rob Naylor BS: Map Projections (33) RE: BS: Map Projections 19 Mar 18

I still have gaps in mine, and I've been studying it for over 40 years! I first did field work with GPS in 1985, when we had 25 minutes coverage a day in most parts of the world.

One country I'm advising at the moment has decided to standardise its CRS in WGS84 based on the ITRF2000 realisation. So its CRS is WGS84(ITRF2000.2000). Data being logged now is in WGS84 based on ITRF2014 at the current epoch (WGS84(ITRF2014@currentepoch)). I'm finding differences of well over a metre at some sites when I transform the data back to WGS84(ITRF2000.2000).

As requirements for precision in seismic surveying, well and borehole drilling and renewables installations have become tighter and tighter, these time-dependent coordinate changes, which we ignored until recently, are starting to show up as issues to be addressed. Which kind of negates the comments I still get from OIMs and the like saying, essentially, " we don't need surveyors any more, we have GPS.....anyone can be a surveyor now...." :-)

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