Changeset: 35203565
ele comma
Closed by Aleks-Berlin
Tags
created_by | Level0 v1.1 |
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Discussion
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Comment from AndersAndersson
Please stop removing values.
There is no need. Fix the renderer if there is a problem with long values.
I can agree that 99% of these values are not that accurate, but some values might be, and then you are reducing accuracy.
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Comment from Aleks-Berlin
Hi Anders,it is not possible today to measure more than 1mm (H-Star) accuray with GPS in Lat+Lon. And Elevation is off by Factor of 10).
Also other methods have are happy with 1mm in best case. Normal GPS is off by about 10 meters in height !
Additionally the surface is not that even.
Even good streets have valleys of 1mm per meter! And natural ground is moving up and down (temperature, humidity, geological) in this range.
So why this sub centimeter precision should be useable?
(in physics we do alot of precision discussions)
http://wiki.openstreetmap.org/wiki/Accuracy_of_GPS_data -
Comment from AndersAndersson
Hello, I know that a GPS does not have that kind of accuracy. But I still don't see the point of editing every ele tag in the world. It creates unnecessary database edits and somewhere you're going to remove a value that actually is known to less than a cm. I don't have an example, and I guess it's the same for you. But if everybody removed things they couldn’t imagine to be important in the database, the database would soon be completely empty.
If we are talking science, then you should know that a lot of bad measurements can give a more exact result by using averaging. If we have 10 height measurements from different, GPS, and different days in a place, I think we should be able to nail the height to a lot better than ±10 m.
If you're problem is that the ele tag is "lying", then we should remove every road, since no road is exactly in the place where it is mapped.
I just don’t see the point of your edits. I (and others) will still be adding ele straight from the GPS, and you will spend your time to clean that up, instead of adding something useful that can improve the map.
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Comment from Aleks-Berlin
I did this one evening. And I only did easyly to find ones (e.g. 9x "9" = 999999999).
1. If limiting datasize is no point and increasing readability by computers, why the many wikipedia:de,:en:fr:es:etc have been worldwide changed to wikipedia = en: ?
Having identical keynames, and same value-string for same meaning should also be pushed more.
2. Averaging of 10001 x GPS (delta = 10m) gives 10 cm final accuracy only (if all people carry their GPS in same height and walk the identical way). And even then: each one in sub-mm gives no advantage.
3. We have many values with more than Angstroem (1E-10m), this is below atom size.
4. Obviously wrong ele-tags, like ele=building, ele=10000, ele=-444,
or obviously bad formated strings like 1.20000000000, 1.300000000001, 4.999999999999, 2.3456789E-5
make no sense to keep them.
5. I added hundreds of ways, buildings, etc, and many GPS-traces, so I think it is unfair to say "you should add something to the project".
6. natural=tree, ele=1.23456 means which point of the tree?
7. If it has been hand carried or from inside a metal-car, noone will ever be able to get much better than a full meter.
8. If a road is off by 1m (vs. satelite) it means it is of by 10m in elevation! -
Comment from AndersAndersson
I will answer you by private message. The messages tend to be a bit to long :)
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