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  #190  
Old March 18th 17, 07:00 PM posted to rec.bicycles.tech
Jeff Liebermann
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On Fri, 17 Mar 2017 17:03:19 -0700, Joerg
wrote:

However, every time I asked dirt
bikers who venture out into the sticks in Nevada they said that they
tried their smart phones but that it really doesn't work well without a
Garmin or other native GPS device.


I've had the same experience when I try to run the GPS in "airplane
mode". The GPS uses location data from the cell sites (AGPS) to
improve its E911 accuracy and shorten acquisition time. Turn off the
cellular part of the phone, or try to use GPS in an area where there
are no cell sites is a problem.

"Using an Android GPS in Airplane Mode"
http://backcountrynavigator.com/using-android-gps-airplane-mode/

There are also issues with the antenna. Size matters and the bigger
patch antennas used in handheld GPS receivers offers much better
sensitivity and view of the sky.

I have a collection of about 10 assorted GPS receivers. Occasionally,
I do a comparison of performance in challenging areas (hills,
mountains, trees, indoors, underground garages, highly reflective
environments, RF polluted environments, etc). If I have a nearby cell
site to use as a starting or reference point, my Moto G smartphone
does quite well. My Samsung S6, not so well but good enough. However,
if I go into "airplane mode" to save battery power, performance sucks.
The main problem is that without the position sanity check provided by
AGPS, the smartphone GPS will produce wildly erratic positions caused
by reflections, often miles away from my actual location. Some of the
handheld mapping GPS receivers do the same thing, but not as badly.

There is also some mapping trickery involved when using maps and AGPS.
In order to improve (or fake) accuracy for E911, mapping smartphone
apps like to round off positions to coincide with a roadway. It's a
fair assumption that someone using a GPS map program would be on some
kind of road. That's great, until you ride off the road and your GPS
tracker thinks you're still on the roadway. So far, it hasn't been a
problem.

You really need to get with the program and buy yourself an iPhone 7+,


Only over my dead body :-)


I'll resist the temptation to say something clever about your
destructive testing methods.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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