> > 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. On Mon, Nov 30, 2020 at 3:45 PM Lindsay Barnes <newsspea...@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 <amadva...@gmail.com> > wrote: > >> On Mon, Nov 30, 2020 at 12:27 PM Warin <61sundow...@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. >> >> _______________________________________________ >> Tagging mailing list >> Tagging@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/tagging >> > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging >
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