shrug-l: Google earth accuracy estimate?

Jim Robeson jim at
Fri Mar 8 09:36:09 EST 2013

Gamins and Tom Tom for vehicles have a good bit of modeling in their display
when using on a street map product; snap to the line.  But they are
typically 3ish meters in a good place and 5-10, maybe even more, in a really
bad place.  Bad being in around buildings or a heavy multipath environment.



Jim Robeson


James M. Robeson

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From: shrug-l-bounces at
[mailto:shrug-l-bounces at] On Behalf Of Sykes, John
Sent: Friday, March 08, 2013 9:28 AM
To: 'Amy Knight'; shrug-l at
Subject: RE: shrug-l: Google earth accuracy estimate?


There are errors when using Google Earth or Google Maps to plot lat/longs in
Florida.  But in my experience they are relatively minor, because Florida is
FLAT!  In my experience elevation differences cause many if not most of the
errors.  The major problems I see involve plotting addresses, where things
may be off by half a block.  If you find the particular building and plot
it, it usually is accurate to about 10 meters or better.  Part of the error
comes from the aerials used and how well they were georeferenced.  Since
most aerials for the State are now being flown with a digital linear
scanner, they are much less prone to these errors.


I just checked my own home, where I have a very visible location on my back
deck that I have used to check several GPS's for accuracy.  Pulling the
Google Earth lat/long quickly (they have a brand-new aerial, shot only a few
months ago) and comparing it to the GPS average was within 1 meter.  T'ain't
too shabby!  Probably 1 ft of that error is my shaky hand on the trackball.
Oh, by the way, they weren't survey-grade GPS's either; 1 Garmin, 1 DeLorme
and my roommate's TomTom.  But I took several readings on different days and
averaged them out.


-- John 



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From: shrug-l-bounces at
[mailto:shrug-l-bounces at] On Behalf Of Amy Knight
Sent: Thursday, March 07, 2013 10:55 AM
To: shrug-l at
Subject: shrug-l: Google earth accuracy estimate?


Hi-  A year or so there was SHRUG exchange of 'bad' google earth examples.
Does anyone know of an accuracy estimate for Florida?  We receive point
location data from many different sources but more and more data are coming
in with Google Earth as the source of the location (lat/long).   We need to
be able to say what locational uncertainty those data have.   How 'off'
could a point be, plotted on Google Earth vs. Florida aerial ortho imagery?
Thanks for any information-



Amy Knight

GIS Program Specialist

Florida Natural Areas Inventory

Florida State University

1018 Thomasville Rd, Suite 200-C

Tallahassee, FL 32303

Ph. 850-224-8207 x214

Science for Conservation


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