Changeset: 125670838
hwys mod.
Closed by seichter
Tags
created_by | JOSM/1.5 (18543 de) |
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source | Bing |
Discussion
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Comment from Silva1989
Hi Seichter,
I hope everything is fine. What is the purpose of this edit?
https://overpass-api.de/achavi/?changeset=125670838
From my understanding It's just a mass deletion of nodes. Is there any advantage in removing almost all of the highly detailed turns of the trail? -
Comment from seichter
To me that was just the conversion of something like a GPS track to a GPS way.
Such a high density of waypoints pretends an accuray that isn't true.
Looking at the trail together with raw data in JOSM, e.g tracks uploaded by other users, the now simplified way follows the trend of these GPS tracks rather well. I couldn't identify any missing turns.There are some slight deviations from arial imagery, but I trust more in a bundle of GPS tracks than in imagery which trends to be distorted in mountain areas.
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Comment from seichter
correction:
GPS track to OSM way -
Comment from Silva1989
Hi Seichter,
I understand your point, as well as your motivations.
I've made the Caldeira Trail numerous times. Once, I recorded the trail with a Garmin Dakota GPS. It has an accuracy of less than 2 meters every 0.5s.
The previous version of the way was already a simplifyed and averaged version of the GPS track. It wasn't particularly sourced from aerial imagery, yes, imagery is very distorted near a ridge.
That's why I said it represented the turns. Yes, a trail like this has numerous turns that can be mapped using such a device. This is useful for runners for instance so that they get a feel of how technical a path can be.
https://forcanasola.blogspot.com/2009/11/ilha-do-faial-caldeira.html -
Comment from seichter
Sorry, a single GPS track does not show the details of a trail even after some simplifying. There is an inherent jitter of more than 2 m even for the latest Garmin 2-frequency devices. If you record the same trail on different occasions you will see the difference,
I am using at the moment seven loggers in parallel, three of them with 2-freq-chips. I then do an weighted average of them. The single tracks have an rms deviation of typical 1 to 3 m, but single trackpoints may often exceed 5 m from the averaged track. The accuracy shown by the devices is always overoptimistic.
In short: You cannot rely on the turns from a single GPS track.
Ways (5)
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