OpenStreetMap

Do it right or not at all

Posted by djanda on 17 March 2012 in English (English)

It's been five days since I started correcting errors/warning on the Northern Cyprus map that I started oh so long ago – and it's been hard!

In a previous rant, I refer to sloppy edits; where individuals are not taking enough care when tracing from satellite imagery. This has a two-fold effect: No relation in reality to what is on the ground and a map that is difficult, if not impossible to navigate. I also have a rather controversial solution which will not be popular amongst the OSM community.

First the poor edits. I have spent countless hours (which I could have used mapping) correcting ways that are not even on highways and such like. It's just a case of taking care when tracing.

Secondly navigation. I believe that the OSM data set took on a completely different meaning when third party apps started to provide us with navigation capabilities. It's serious stuff. And if there are crossing ways, unconnected nodes and such like then it's not going to work.

Solution? Don't edit! That's right. Don't edit. In terms of man hours I have spent correcting I could have done the job myself. It's hard to say but that's the bottom line. Of course there are those who will say that it's just a question of educating users. But having looked at the “efforts” of some, I wonder if it's education or vanity (oh! Look at what I have done) that is the issue.

Location: Yay Sokak, Ozankoy, Kyrenia, Turkish Republic of Northern Cyprus

Comment from Sanderd17 on 17 March 2012 at 17:16

I don't agree.

I've corrected a lot of mistakes too, and I've always done it with pleasure.

When I saw a complete network added to OSM, but without any node connected, I contacted the user and told him what was wrong, then I used my experience to repair it with ease.

When I saw streets added with wrong tags (e.g. unclassified instead of path), I contacted the editor, told him what was wrong and corrected it.

I'm constantly guarding my own surroundings, and I try to help users when they make a mistake. But I always encourage them to keep editing, as that's the only way our user base will be big enough to keep the database maintained.

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Comment from compdude on 17 March 2012 at 18:39

That seems a little bit mean to say to someone. Rather, inform the user who created the way of their mistakes so that they will hopefully learn from it and do a better job in the future.

Also, keep in mind that some of the roads may have been traced long ago when the satellite imagery was lower resolution, and the person may not have zoomed in that far (because it would have been all pixelated), thereby resulting in roads there being fairly "off." Or, if there wasn't even satellite imagery for the area, and they might have been using a GPS. Keep in mind that although GPSs are generally more reliable than the aerial imagery, they aren't perfectly spot-on. In fact conventional GPS devices have a margin of error of several yards.

Also, if you don't like cleaning up after other users' mistakes, don't waste your time doing things you don't like to do. There's no need to let that get in the way of what you are really interested in doing.

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Comment from ianlopez1115 on 18 March 2012 at 05:17

Honestly, I have problems with some mappers in my "areas of responsibility". However, I'll have to agree with compdude and Sanderd17 - inform them of their mistakes and encourage them to fix their edits. If that fails to "educate" them, then fix the various problems (unconnected roads, self-intersecting ways, open polygons) on sight.

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Comment from z-dude on 18 March 2012 at 09:05

There's more to OSM than tracing satellite imagery which may not be calibrated to GPS tracks on the ground or may be out of date.

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Comment from djanda on 18 March 2012 at 14:34

@ alexz Did I imply there was not?

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Comment from z-dude on 18 March 2012 at 17:51

Yes, you implied that tracing satellite imagery was the main priority.

What frustrates me when mapping is when I map out a trail using an accurate gps, and backtrack so that there are multiple tracks to reduce noise, spending a couple of hours to find that someone has gone and traced from misplaced imagery, or imported low resolution tracks from CANVEC.

When you use a GPS with 10 foot accuracy, and go over a trail multiple times, and filter out the outliers, and average out tracks, you end up with a more precise location than Bing or Yahoo imagery will provide.

When I look at a path such as http://www.openstreetmap.org/edit?lat=35.320155&lon=33.34458&zoom=18 and look at the GPS tracks, I see what appears to be two pairs of repeatable gps tracks taken by a pedestrian or cyclist on the edge of the roadway, and the roadway is not centered between those two pairs of tracks.

This makes me think that you are tracing imagery which is not accurately placed.

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Comment from djanda on 18 March 2012 at 18:13

@ Alexz No I did not. What I stated is that a priority is to correct mistakes made by others using Pot latch. The only person who has traced with GPS data is myself.

I understand your frustrating with sat tracing over valid GPS data but please do not bring that to this conversation. For the record, when I came back to the map and noticed the high resolution imagery I did a two day four track calibration test to see if the imagery is accurate - it is.

The track you refer too was made by myself using a Nokia N95. Damned good but with an offset I could never fix.

And the whole crux of this is that I would have my feet on the road mapping - but am clearing up others mess.

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