Why do some people just upload a new track without any regard for a track that's already there? I've seen areas that I've mapped show up with an overlapping track. Every time I upload, I download first, and if the track is already there, I just edit the existing track and then remove mine before uploading the changes. Then if the original track seems to be the same as mine without much change, I assume it's just a difference in GPS software, and I make no changes.
After a while of people just randomly uploading whatever they have, the database could wind up with 20x more data than is necessary or more. I've already edited areas that had the same road uploaded 4 or 5 times.
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My other comment about laziness deals with people using the aerial photo in the online OSM editor without actually visiting or GPS tracking the area.
I've gone through efforts to actually GPS map areas that are new construction. Places that the roads and bridges have been completely moved.
People go into the online editor and think that the aerial view is still correct, but it's out of date. I've ridden the areas. I know that what I've put there is correct. Why do people insist that the map is right if they've never been there?
When I started participating in the OSM project, I read all of the guidelines, and one of the primary ones was "if you haven't been there, don't update the map". Well, it seems that a lot of people are doing just that.
It would be nice if there was a way to prevent people from just uploading their GPX files. Force them to actually LOOK at the map they're about to modify. Heck, maybe even remove the aerial photography so that it forces people to actually go to the place they're trying to change.
Sorry to rant, but I've just seen hours of my work erased because some jerk thinks the aerial photo is correct. :(
The coordinate that I've listed is where I had placed a traffic circle. This whole area has been under construction for over a year, the aerial picture is wrong. But the map has been changed to match the aerial photo again.
This is very annoying.
-Laura
Discussion
Comment from lyx on 21 August 2009 at 21:37
I suggest you try to find a street that has been modified and use the item history to find out who did the change. Contact the user and tell him that his work was not really helpful. I blame most of these cases not on malice or lazyness, but people being both enthusiastic and clueless. Hopefully it's possible to give them a clue without demotivating them.
Comment from davespod on 21 August 2009 at 21:49
I symphathise with your point about people changing areas you've mapped just based on the Yahoo aerial photo. But with regard to GPS tracks, surely given the inaccuracy of consumer GPS devices, a second and third opinion can be very useful? I'm afraid I am guilty of uploading tracks where they already exist, and indeed sometimes uploading the tracks of my local streets more than once, as I can then go with the middle ground if the tracks vary slightly (no Yahoo in my area to cross-check with).
Comment from andrewpmk on 21 August 2009 at 22:41
In many areas Yahoo imagery is more accurate than GPS traces, if the area hasn't changed since the photo was taken and the photo is aligned properly (or is aligned manually to the GPS trace in the editor). Remember that consumer GPS isn't all that accurate. In general, I recommend comparing both sources with what is actually on the ground and using whichever is more accurate.
Comment from Laura Vance on 21 August 2009 at 22:57
If the photos are from Yahoo, then aren't those copyrighted? Isn't it against the OSM guidelines / rules that the map be based on ANY copyrighted information? So by aligning the OSM map with the Yahoo imagery, isn't that basing an "open" map on a copyrighted source? (I checked maps.yahoo.com, and their data comes from NAVTEQ, and they have a copyright 2009 by Yahoo, Inc. on the bottom of the map, so it appears to be copyrighted and private, not public and open)
I may be wrong, and if I am, that's ok, but I wouldn't align it with the images just for that reason.
Yes, I know consumer GPS is not perfectly accurate. Yes, I know that multiple paths are preferred and take the average. However, I do that editing in JOSM and upload the edit, not upload multiple tracks.
I know that my feeling about projects like this is not the normal, but when I got my GPS, and learned about OSM, I read all of the instructions before I made my first upload, and when I stared seeing multiple routes being uploaded for the same path, I started editing those areas to reduce it to a single "way".
If everyone would read the instructions, it would be isolated incidents.
Comment from Laura Vance on 21 August 2009 at 23:02
From the OSM wiki regarding copyright: http://wiki.openstreetmap.org/wiki/Copyright
excerpt:
Do not use data from copyrighted maps or any other proprietary data! So copying, tracing or any act of reproduction of any copyrighted work is strictly prohibited.
That made me wonder why there's an aerial photo under the map, but I've refrained from using it.
I do apologize for being bothered so much by this, but this seems like people are completely disregarding the desire to produce a 100% "Open" map.
What happens if someone informs the Yahoo legal department that the OSM project is using their images for an open map project?
Comment from Laura Vance on 21 August 2009 at 23:02
If the photos are from Yahoo, then aren't those copyrighted? Isn't it against the OSM guidelines / rules that the map be based on ANY copyrighted information? So by aligning the OSM map with the Yahoo imagery, isn't that basing an "open" map on a copyrighted source? (I checked maps.yahoo.com, and their data comes from NAVTEQ, and they have a copyright 2009 by Yahoo, Inc. on the bottom of the map, so it appears to be copyrighted and private, not public and open)
I may be wrong, and if I am, that's ok, but I wouldn't align it with the images just for that reason.
Yes, I know consumer GPS is not perfectly accurate. Yes, I know that multiple paths are preferred and take the average. However, I do that editing in JOSM and upload the edit, not upload multiple tracks.
I know that my feeling about projects like this is not the normal, but when I got my GPS, and learned about OSM, I read all of the instructions before I made my first upload, and when I stared seeing multiple routes being uploaded for the same path, I started editing those areas to reduce it to a single "way".
If everyone would read the instructions, it would be isolated incidents.
Comment from Laura Vance on 21 August 2009 at 23:04
my comments above are out of sequence... it looked like a server error.
Comment from es_ka on 21 August 2009 at 23:19
Don't worry about Yahoo copyright. There is an agreement allowing us to use their aerial photos. See http://wiki.openstreetmap.org/wiki/Yahoo#Legalities for more info.
And I'm not sure, but I think there's a difference between the photos on maps.yahoo.com and the ones OSM uses. Maybe the latter ones are older or with less resolution...
Comment from wallclimber21 on 22 August 2009 at 00:44
My personal take on this is slightly different:
- Obviously, adding a new WAY without first checking if it's already there is bad. Not sure if this is what you were complaining about?
- But uploading a GPX track for a given area, even if it's already there, is very positive. This is especially so for mountainous regions where GPS is less accurate, but it's true in general. It allows one to make judgments about the accuracy of data. Mass data storage is cheap. A bit of redundancy in GPX data won't hurt.
E.g. sections of the Tahoe Rim trail have been uploaded 5 times or more. I love it!
- I've move literally tens of thousands of edits in cities all over where I've never been: the US is a big place and there are uncountable number of cities that have never been touched. We're lucky to have TIGER data, but the data is only mostly correct from a topological graph point of view. So there is a lot of value in selecting a city and starting to align this graph to the situation on the ground. It's very rare to stumble on places where edits have already been made and it's usually obvious also, so that's something where I tend to keep my hands off.
Note that the US sectio nof the wiki specifically encourages to align TIGER data, even for places where you've never been.
A nice example is the city of Fresno, CA: pretty large and almost completely unedited just a few months ago. It took me many weeks to align thousands of streets correctly, but the result is a much higher quality map.
I don't know if I've deleted some other smallish edits in the process, but if so, then that's too bad. A little bit of collateral damage is a price to pay in a cooperative project.
I've seen it happen with some of my own edits. Usually I send a friendly message to the one who did and things can be resolved easily. (They're almost always enthusiastic beginners who don't quite know yet what to do.)
Tom
Comment from Skippern on 22 August 2009 at 01:31
I agree that changing roads because they do not fit with the yahoo images is bad, especially if the yahoo images are old and the shape of the road indicates a rebuild of the road.
GPX tracks are very good and usefull, though there should be a way to filter the age of each trackpoint. At the moment all uploaded trackpoints can be downloaded, and this can make areas very crawded. Especially if there have been road reconstructions or if the area suffers from urban canyon effects.
IMO Users should also be able to blackspot areas when uploading GPX tracks, so that overcrawding of inaccurate trackpoint around users home areas can be avoided. (I would love to have 250m blackspot on my house)
Comment from Laura Vance on 22 August 2009 at 01:36
cool, then if that's the case, I still think there's a danger of people working on the graphic when a human has already mapped an area that has changed with a GPS.
I apologize for my earlier comments... I was a bit moody when I realized that hours of work had been completely discarded. I still wish everyone would do it the right way, but I'm not as upset about it as I was earlier.
Comment from HannesHH on 22 August 2009 at 06:53
I am not sure if you are really talking about GPS tracks or if you called the OSM nodes/ways tracks. Those are two independent things.
If you do indeed mean GPS tracks, then the more the better. The Yahoo images actually are sometimes quite inaccurate (at least where I live) so good mapping must be done by multiple GPS tracks here.
Comment from dmuecke on 23 August 2009 at 18:42
Try to get in contact with those mappers overwriting your work. In most of the cases it happens unconsciously.
Comment from Sensei Marc on 23 August 2009 at 22:06
I see improvements in the OSM Map daily, and it appears to be in a positive direction. Don't discourage people from contributing. There is no doubt that some errors will creap in but largely from new contributors who are still learning as I am.
Comment from france-59-valenciennes on 23 August 2009 at 23:41
totally agree .Same problem without raster graphic use . it is why device for record gpx must support record gpx and view in the same time the last osm map. it ll be nice to have osm article that speak this ; perhaps an article already exist , let me know if your use own .
Comment from davetoo on 24 August 2009 at 04:57
Laura, I'm confused about some of your references to GPX; simply uploading raw GPX to the Public GPS Traces area does not mean that the map/database will be modified. Or are you suggesting that people are using JOSM to convert their GPX tracks into OSM ways and just uploading them without regard to the existing data? I would be surprised if that practice is widespread; I would expect that the overwhelming majority of people using JOSM know enough about OSM to understand the impact of their edits.
Comment from daveemtb on 24 August 2009 at 10:27
There seems to be some confusion here about the difference between tracks and ways. Tracks are GPS data, stored in GPX files. ways are the data stored in the database that show up on the rendered maps.
Uploading traces for areas already mapped is helpful. Converting them to ways without checking that there aren't ways already there is unhelpful.
I too have had problems with tracers "correcting" my work. You need to contact the people who do that and suggest that they don't change things based only on tracing. Tracing new areas is helpful, but changing existing work based on very old photos is unhelpful.
Comment from daveemtb on 24 August 2009 at 10:49
ps: see: http://www.openstreetmap.org/user/daveemtb/diary/6399
Comment from Laura Vance on 24 August 2009 at 15:26
I'm not talking about the traces, I'm talking about on the map itself. Ways are being added by people using JOSM and simply uploading their GPS track. Or they are possibly making the same mistake that I made with JOSM my first time too (which I corrected as soon as I realized what happened).
I loaded my GPS track into JOSM. I downloaded the map data for the area. I edited the existing road. I uploaded what was in my JOSM editor. When the map was re-rendered, I noticed that the road had its name alternating with "nn". I realized that I needed to delete my GPS "way" from JOSM after I edited the existing way before uploading to avoid this type of error. I asked a question about multiple ways being uploaded, but nobody seemed to know what I was talking about, so I figured it out on my own and corrected my mistake. Based on the response I got, I can only assume that most people don't believe that it can happen, or that OSM can tell when there are multiple ways and merge them automatically (which would be great! :) ).
Since I did that, I've seen several times where I've driven a route to get my GPS track to edit a way in JOSM. As I'm editing, I notice that an adjacent way has several ways uploaded. I think one I edited had 4 overlapped ways for the exact same physical road.
I don't upload my GPS tracks directly to OSM, I just use them to edit ways in JOSM and upload the edits. I also haven't traced from the Yahoo images either.
Comment from Wynndale on 24 August 2009 at 17:55
The new Bad data proposal is a scheme to mark traced aerial photography or maps as out of date or otherwise unreliable so that they can be obscured in editors and users don’t copy details into the OSM database reducing its accuracy.
http://wiki.openstreetmap.org/wiki/Bad_data
Comment from Minh Nguyen on 25 August 2009 at 06:53
How about spelling out “YAHOO!’S WRONG” using a series of tagless POIs?
;^)
Comment from davespod on 25 August 2009 at 12:40
I now understand your annoyance if people are actually uploading duplicate ways. I have never seen that happen.
By the way, I always upload my traces simply to show the source of the data. I see this as important for a number of reasons:
a) I believe people are far less likely to alter the ways based on a less reliable data source (dodgy GPS trace or out-of-date Yahoo) if they can see the original data source.
b) As further traces are uploaded for the same road, we exploit the "herd intelligence" and alter ways to go for the average (whether mean, median or mode), as it is unlikely any one track is absolutely accurate (obviously, we would ignore the extremes, and anything suspiciously zig-zagging). Thus we can increase the accuracy of the map.
c) If there is any future claim of copyright infringement, regardless of who is defending it, they will have reasonably sound evidence that the area was mapped on the ground, and that the ways are based on those traces.
I do hope if you don't do this, that you do add a source=survey or source=gps tag (not needed if you upload the traces). It really annoys me when I have no indication of the source of a way which contradicts my GPS traces. I tend to mail the person responsible to ask the source before editing*, and hope they reply, but not everyone would be so patient.
* My logic being that if the source was an out-of-copyright map then my GPS trace is probably more accurate, but if it was another GPS trace I am not usually willing to assume that my trace is any better.
Comment from Laura Vance on 26 August 2009 at 04:05
That makes sense about uploading the GPS tracks. I keep all of my track files after I edit, so it won't be difficult to go ahead and upload them all.