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I always find these edits fun to see. Typically a node gets moved a few feet.

With my Garmin Oregon, I typically get a very repeatable track with a clear sky. It’s when you get 200 foot tall giant trees that tracks differ by more than 10 feet.

I do have a question: with the Glasnos GPS systems, is the accuracy better? I hear that it’s supposed to be better in the areas where you ave tall trees and canyons. Has anyone tried mapping with the new Garmin Glonass devices yet?

Location: Suncrest, Burnaby, Metro Vancouver Regional District, British Columbia, V5J 1Z3, Canada

Discussion

Comment from smsm1 on 14 July 2012 at 09:39

To really improve accuracy you need a really, really expensive professional GPS, which you stand for a few moments in a place while it averages out any error. In some council areas in the UK, the bus stops that we have imported have been done to this accuracy, which annoys them when OSMers adjust them based on their little inaccurate GPS.

Comment from Opk on 14 July 2012 at 16:20

Glonass is supposed to be better at extreme latitudes and in the cases you cite: tall trees and canyons. Otherwise it just gives you extra satellites to get a signal from. Galileo should in theory make a bigger difference once it is operational. Reviews of the new Garmins with Glonass don’t seem to indicate that they are much better but that may improve with newer firmware versions.

For trees, coming back in Winter to get new GPS traces can make a big difference.

Comment from kevjs1982 on 14 July 2012 at 18:14

I’ve noticed on my mobile when it has Glonass activated it gets lock much much faster than with GPS alone* (although this might be down to the half a dozen listed Glonass satellites each showing a stronger signal than any GPS one) - doesn’t seam to be any more accurate in the main when standing still, but when moving about seams to draw much straighter lines (when walking on a straight road that is!). When indoors at home or work (near a window) I tend to see half a dozen Glonass satellites and just a couple of weak GPS ones.

In the city centre it will gain lock within seconds of turning the “GPS” on compared with my Garmin GPS (only) receiver that can take minutes.

*even with GSM, 3G, and WiFi deactivated.

Comment from z-dude on 14 July 2012 at 19:24

The faster start up times of the Euro and Glonass systems are because of the message formatting of their GPS signals is different. Modern GPS’s store satellite almanac data in memory for a warm start (otherwise there will be a minute warmup time - they may wait for the 12.5 minute signal), but they typically have to obtain more precise satellite location data which is broadcast every 30 seconds. http://en.wikipedia.org/wiki/Global_Positioning_System#Communication

Comment from Vincent de Phily on 16 July 2012 at 09:48

Remember that nearly all trekking devices have an “average waypoint” feature that will wait for a bit until it’s sure that the measured position is correct. And you can take extra measurements a few hours or days appart.

It may not be as good as those overly-expensive professional GPS, but it’s more than enough for mapping in most cases. You won’t trace a road with it, but it’s perfect for alingning imagery.

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