<div dir="ltr"><div>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: <a href="https://www.openstreetmap.org/user/bobwz/diary/394711">https://www.openstreetmap.org/user/bobwz/diary/394711</a></div><div><br></div><div>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.</div><div><br></div><div>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.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Nov 30, 2020 at 8:36 AM Andrea Mazzoleni <<a href="mailto:amadvance@gmail.com">amadvance@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Nov 30, 2020 at 12:27 PM Warin <<a href="mailto:61sundowner@gmail.com" target="_blank">61sundowner@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>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.
</div></blockquote><div>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.</div><div><br></div><div>To give you an example, my eTrex device reports 3m of precision, the new GPSMAP 65s reports 1.8m.</div><div>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.</div><div></div><div></div><div></div><div></div><div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><p>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.
</p></div></blockquote><div>I bought that new device exactly due the frustration of always seeing a different recording...</div><div><br></div><div>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.</div><div></div><div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><p>imagery may well be
better than survey by consumer GPS</p></div></blockquote><div>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.<br></div></div><div></div><div></div><div></div><div><br></div></div></div>
_______________________________________________<br>
Tagging mailing list<br>
<a href="mailto:Tagging@openstreetmap.org" target="_blank">Tagging@openstreetmap.org</a><br>
<a href="https://lists.openstreetmap.org/listinfo/tagging" rel="noreferrer" target="_blank">https://lists.openstreetmap.org/listinfo/tagging</a><br>
</blockquote></div>