shrug-l: Google earth accuracy estimate?

Fri Mar 8 11:34:45 EST 2013

I've found that Google Earth is wildly different based on the area you
choose.   They have New York city tied down pretty well.  That may be
good if Sweet Pea [the no-too-smart manatee] still goes to see the
statue of liberty each year.     It's clearly not as detailed in
suburban areas and most of Florida. 

I may be equating higher detail with precision with no way to measure
it, but I assume if the aerial photo source shows much better detail
then precision matches it.  It is beyond my knowledge and expertise be
sure this is true. For all I know Google has their own version of a
digital "selective availability"  type fuzziness added so terrorists
will miss the Halliburton Office and get the tea room next door. Maybe
the resolution I see using it as a street map is the upper limit. 

From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Jim Robeson
Sent: Friday, March 08, 2013 9:31 AM
To: 'Amy Knight'; shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Google earth accuracy estimate?

I would say the accuracy for the location of an endangered species would
be acceptable.  The problem might be more of individuals who have no or
little photo interpretation experience placing a point in an area with
little of no ground features to accurately identify their location on
the image.   As for a number, I don't have one.  A lot might depend on
their level of support on Google Earth; are they paying for the upgraded
version?  

There is the old cartographic trick and that is make the point symbol
sized proportionally to the confidence in the data accuracy and quality.
A point that is 200 feet across covers a lot of sins;  the same with a
200 foot wide line.   The is the modern day equivalent to using a magic
marker of a blue line map.   Most never realized that, that line could
be a couple hundred feet wide.  

So, sadly I don't have any numbers on Google Earth.  I suspect given the
kinds of errors that we all shared, any number might be rather dubious.

Regards,

Jim Robeson

James M. Robeson

Mapping/GIS Sales, Trimble Certified Trainer  

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From: shrug-l-bounces at lists.dep.state.fl.us [
mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Amy Knight
Sent: Thursday, March 07, 2013 10:55 AM
To: shrug-l at lists.dep.state.fl.us
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  

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

www.fnai.org

Science for Conservation

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