[Tagging] How to tag for dualband GPS ?

Warin 61sundowner at gmail.com
Mon Nov 30 23:43:32 UTC 2020


On 1/12/20 7:46 am, Andrea Mazzoleni wrote:
>
>     I recently wrote a series of diary entries about my experience
>     with the accuracy of one-device GPS precision. I concluded with a
>     comparison of three devices I had personal experience with
>     including a new Garmin GPSMAP 66sr which I posted here:
>     https://www.openstreetmap.org/user/bobwz/diary/394711
>
> Very interesting!
>
> Here you can find the mapping of my tests with GPSMAP 65s and eTrex 30x:
>
> https://ibb.co/bKvpxYG
>
> It's a circular trail repeated 5 times with one point every second.
>
> I repeated it again with the recording frequency set to Auto, and the 
> GPSMAP lost a bit in accuracy, so better to stick to one point every 
> second.


Think your confusing two terms;

resolution


accuracy


With increased points along a way there is increased resolution.

The accuracy does not follow with increased number of points unless they 
are all for the same location so averaging those points reduces noise 
thus increasing accuracy.

>
> On Mon, Nov 30, 2020 at 3:45 PM Lindsay Barnes <newsspeak11 at gmail.com 
> <mailto:newsspeak11 at gmail.com>> wrote:
>
>     I recently wrote a series of diary entries about my experience
>     with the accuracy of one-device GPS precision. I concluded with a
>     comparison of three devices I had personal experience with
>     including a new Garmin GPSMAP 66sr which I posted here:
>     https://www.openstreetmap.org/user/bobwz/diary/394711
>
>     In short, multi-band and multi-GNSS devices do offer in an
>     increase in precision and accuracy and we're seeing this become
>     more common in a standard smartphone. However, that level of
>     precision is not necessary in most cases. It is most helpful in
>     areas without good satellite imagery coverage or where imagery
>     lacks reference points (like in wooded trail areas, as mentioned).
>     This is compounded by the fact that one GPS device has a floor to
>     how accurate it can be due to the nature of the system and
>     interference from the natural landscape, as was mentioned.
>     Furthermore, mult-band and mult-GNSS chips are becoming more
>     common in smartphones and I would expect this level of precision
>     available to most mappers without the need for specialty equipment
>     over the next 5-ish years.
>
>     To answer your question about tags, a comment can be added in the
>     source field of a changeset, but in my opinion most mappers will
>     not dig too deep into a change to determine how precise the mapper
>     may have been . Satellite imagery is generally used as the source
>     of truth and if a mapped feature varies substantially from the
>     imagery, mappers are inclined to move the feature to match imagery
>     without researching how the feature was initially created. The
>     good news is that if satellite imagery in unclear or lacks
>     reference marks, mappers will usually leave features alone unless
>     they have personal knowledge of an area or are working off a
>     tasking manager.
>
>     On Mon, Nov 30, 2020 at 8:36 AM Andrea Mazzoleni
>     <amadvance at gmail.com <mailto:amadvance at gmail.com>> wrote:
>
>         On Mon, Nov 30, 2020 at 12:27 PM Warin <61sundowner at gmail.com
>         <mailto:61sundowner at gmail.com>> wrote:
>
>             If the intention is to indicate the
>             error/accuracy/uncertainty then tag/state that. The better
>             GPS devices give indications of this
>             error/accuracy/uncertainty.
>
>         The big advantage of the dualband is not (only) the increase
>         in accuracy but the ability to work in not optimal conditions,
>         like under a clif or other obstacles where you have reflected
>         GPS signals.
>
>         To give you an example, my eTrex device reports 3m of
>         precision, the new GPSMAP 65s reports 1.8m.
>         But reality is that I saw errors up to 50m with the eTrex.
>         It's also difficult to know the precision because it changes
>         while moving, and it's not recorded in the track.
>
>             If possible take tracks of home to/from work and compare
>             them to see how much they vary day to day ... they should
>             give an idea of problem.
>
>         I bought that new device exactly due the frustration of always
>         seeing a different recording...
>
>         My initial tests are really encouraging. Yesterday I repeated
>         10 times a trail under the woods of a hill, comparing the
>         results of the eTrex and GPSMAP 65s, and the dualband one has
>         the recorded tracks a lot more consistent. Something like 10m
>         vs 2m thickness.
>
>             imagery may well be better than survey by consumer GPS
>
>         I agree. Where an image is available I always use it as
>         reference. But most of the trails of my local area are under
>         the woods (low mountain) and the GPS is the only source of
>         information.
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20201201/fbf266e3/attachment-0001.htm>


More information about the Tagging mailing list