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Google Earth vs GPS
by Simon at 09:08 30/10/06 (Blogs::Simon)
Having finally managed to hook up my old Garmin GPS III+ to my Mac using a KeySpan USB-Serial converter (model #USA-19) and a Garmin RS232 lead (NB: requires installation of KeySpan's USB-serial drivers), and importing all the waypoints and tracks the GPS has stored, I'm somewhat disappointed to see just how innaccurate Google Earth's image positioning really is.
It's only to be expected, I suppose, given perspective issues, but somehow I feel the All-Powerful Google has let me down here.

The image below shows the waypoints (WGS-84 datum) for the Stonehenge Station Stones overlaid on Google Earth's image of Stonehenge.

The red dots are the actual Station Stones, and the white markers are the waypoints I recorded for the them when we were there for the southernmost moonrise in July this year.

No point me tramping all over the landscape, GPS in hand, expecting to be able to use GE for any kind of accurate analysis then - shame!

GPS Waypoints imported into Google Earth  showing discrepancy in their image positioningThat's way out!


OK, OK, I recant of my disappointment in Google in light of reflection on the inherent inaccuracies in GPS (grid drift, selective availability, waypoint averaging being pointless etc) kindly pointed out to me elsewhere.

JPG image (14 K) GPS waypoints imported into Google Earth
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