Hi folks, I think our meeting was worthwhile and it was really good to put faces to the user names. Stephan took copious notes, so I won’t put a summary here, in case he wants to do it.

I do want to share what I just found and commented on: https://www.openstreetmap.org/changeset/63105877

Feedback is welcome. Am I on the right track?

Kind regards,

let’s have a short summary of our meeting yesterday in Chiang Mai.

While there are multiple issues observed with the way data is mapped by Facebook (like number of nodes on ways not justified with the geometry, e.g., sometimes too few, other times too many), there are issues with the tagging of roads like potentially tagging driveways as residential or agricultural tracks as residential. Or unconnected highways where different imagery could have indicated a connection. Also sometimes trusting too much the positional accuracy of the imagery layer without cross-checking the alignment to GPS tracks.

The most annoying problem had been identified as agricultural tracks being classified as unclassified (or residential), providing routing software a good alternative to the proper roads by saving a few meters of distance. This also happens in case of a missed turn when the routing tries to bring you back on track and suggests to cross through some fields to U-turn.

As we have no good statistic about how frequent these problems really are, we decided to largely extend the changeset comments on discovered problems instead of reporting the issues in private messages or simply fixing them.

We also agreed that once a way was verified by a community member on the ground we are removing the import=yes tagging on the element.

We are also going to cross-check a random sample of these highways to get some numbers regarding how frequent such problems are. I will provide some tolling for this.
I will also provide a style for JOSM to highlight Facebook roads.

For checking changeset discussions, see here an overview of the last comments for Thailand:

To get all discussions involving a specific user, go to

and search for the username. Click on the link to view the commented discussions, then remove the “&commented” part from the URL. Maybe someone knows a more direct way to come there by knowing only the username and not id.

It was also asked how to see where a specific user has edited. The hdyc site from above can give some hints already. For details, you could search in the data, see here for an example: https://overpass-turbo.eu/s/CGY

To visualize changes, have a look at this: https://overpass-api.de/achavi/

yes, detailed comments like this help. Maybe not immediately fixing the things makes it easier to see what was actually done wrong.

Regarding way 629622938 intersecting with 2006:
After reverting your move of the node 5944737115 in changeset 63441790 it is not looking this bad. Facebook might have used the existing node instead of creating a new one but not that bad that I would have had complained.

Other points you had mentioned are correct. I added some more comments in that area…


Sorry, you lost me here. This is what it looked like before I touched it:


I think this is actually the most serious error of all.

(What is it with this forum s/w that it often displays part of the URL instead of the picture?)

I think you refer to a problem with the way attached to node 5944737115 intersecting the highway 2006, also making two right-angle curves in way 2006. Are you? If this is what you actually describe as a problem, then it was your move of the node to create the problem. My screenshot above shows the geometry after I revert you node move. Probably you accidentally moved the node when trying to pan the map.

Here is the history with a visualization of you moving the node four meters:

The current state of the map no longer shows this as I merged the road junction into the already existing node next to it.

I suspect that this node got moved with the whole area, when I adjusted the offset. I didn’t move the main road, as it was already correct and of course I have to click each node separately and if two are very close together then one of them will not get selected, as it’s not visible. I checked the history of both nodes and I was sure I my name didn’t feature in it, but who knows…

I’ll go and update my comment then.

Thanks for investigating.


Just a quick note to say thanks for the detail that people are adding in changeset discussion comments - that’s exactly what’s needed.

As promised on our meeting, here is a small map style for JSOM to highlight elements having “import=yes”, so in the majority of cases coming from Facebook.

The location is probably not forever, but I can leave the file there for the next few months, so you can directly add the following URL to JSOM as a map paint style.


Thank you very much for the map paint style Stephan — it highlights the imports very well.

I visited a small town today, Ban Pin North, and didn’t really intend to do any major editing there but did want to add the name of the town to OSM. When I looked at the area in question using your paint style, the imports showed up very well. While there were no gross errors caused by the FB operator, my assessment is that many ways were carelessly drawn. The work, done about a year ago by RVR009, was generally not anything I would have wanted to have associated with my name.

I did not bother to write a changeset comment because my assessment was rather general and the work was done a year ago. Using GPS traces I adjusted the offset of the DigitalGlobe Standard imagery, and aligned ways (not all of which were created by RVR009), made a few obvious connections and removed the “import=yes” tag from the ways I checked.

I uploaded the imagery offset I used into the Imagery Offset Database as Ban Pin North.


I actually used to be indifferent to armchair mapping and imports, but recent encounters changed my mind.


I really feel you now @Russ McD, @Tom Layo; one won’t see the reality in accuracy of these entered data unless one actually “live there”. Even the normal “imports” are usually based on data observed from on-the-ground. These corporate players seem to blatantly ignore the fact that fixing a map full of faulty data is much harder than adding correct data to a blank slate.

As a local resident in Bangkok, I had a recent run-in with corporate-based armchair mappers. In my case it’s Grab ridesharing company.

Their amount of changsets are much smaller than ones made by Facebook et al (around the magnitude of ~100 changesets); and as far as I know, they are 100% human-based team, not some nameless AI robots.

I began to notice the existence of their campaign, not because of their announcements, but due to the “obvious wrongs” that have been recently appearing in the area that I personally frequent to.

So I got curious, and began to do a proper on-the-ground verification of their edits: the result is not pretty.

With only just few samples, verified against ground observation, I found:

  • Overwrite of ground-surveyed data; broken local consistency.

  • Mis-upgrading of road levels (e.g. existing footway being upgraded to “service” despite the actual uses).

  • Mis-tagging of newly-added “roads” (e.g. new footway being tagged “service”); disastrous for routing.

  • Nonsensical objects tagging (e.g. a temple being re-tagged as road); ruined rendering.

Most of these “oops” are simply invisble from the satellite imagery, but glaringly obvious when you actually visit the place. Sifting through changsets and visiting places in their edits to fix them are like going down the rabbit hole, there’s no end of errors in sight.

And of course, I chided them directly in changset comments whenever I found these errors. But there are so many changesets that these will take several years to verify, in downtown Bangkok alone. Doing these erodes my sanity.

To date, I have verified just around < 0.5% of the edits done by their campaign. I estimate the count of errors in whole are to be many, many more. My current “verdict” is along the line of @Russ McD: the affected areas are now tainted; these can’t be trusted by satnav users anymore.

These are all I can say about corporate armchair mapping, from a very small subset that I actually went into the field to verify; now scale it to the entire rural Thailand.

Speaking of the scale of this “import” problem: don’t anyone realize that at the moment, amount of OSM edits from Facebook went through the roof and is now ranked as #1 in Thailand?

This is not a problem of AI; it is a problem of industrial-scale armchair mapping with zero ground-based verification. They are leaving their mess for us unpaid contributors to fix, case-by-case, for a several lifetime.

I condemn Facebook for this massive scale of data vandalism, and OSMF Data Working Group for their inaction.

With these, while I won’t quit contributing to my area in Bangkok, I don’t have the heart to recommend OSM for general uses in Thailand (and much less with satnav use) to anyone, anymore.

The damages are done. As a local user, my position on this is a firm: speedy deletion.

Erm - has anyone ever reported problems in Thailand with GRAB or Global Logic (their contractor) to the DWG ? I’m not seeing any tickets, but there may have been informal contact. I’m aware of reported problems in Indonesia (see e.g. https://www.openstreetmap.org/user_blocks/1882 and https://www.openstreetmap.org/user/harrymahar/diary/43671 from earlier this year), but nothing from Thailand.

For completeness - the list of GRAB contractors that I am aware of is at https://github.com/GRABOSM/Grab-Data/blob/master/Grab%20Data%20Team .

If there are current issues that need investigating with GRAB users please let us know. To be useful what we need are links to problem changesets and a description of what the problem is. Also if possible, with a changeset discussion history that shows that you reported the problem to them and they did nothing about it.

Please keep this thread strictly about Facebook edits. Please comment in detail at changesets what they did wrong. refer to the OSM id of the elements in question. Maybe even take a screenshot (snipping tool in windows). postimages.org allows hosting of them.

This is the task for Grab:

Also comment here on changesets. As up to now we have very little to no complaints about them (they are not that active around Chiang Mai), please refer to commented changesets there as well.

I’ve just reviewed Yasothon province where I worked for 2 months. FB has changed many of my unclassified roads to tracks. Some are 8-9 meters wide, connect villages, nothing about them is agricultural. Then never contacted me before changing, something I would have done.

I wrote comments, and will change them back if FB doesn’t.

Hi Tom,

Changing community data like this was completely against our editing policies and the editor should not have done it. I believe I have reverted most of the tag changes and will continue to clean up anything else I find. Thank you for bringing this to my attention.

Thanks, Jeff

But I am wondering, do we have to point out every error? Because it’s usually easier to just fix them than to post a comment.

If we have to do this, I am in favor of a major revert.

Is FB willing to do a review of all their additions/changes? You have all the data, we have nothing but random checks.

I hope you can see the problem for us.

Regards, Tom

Hi all. I completed a small software to collect statistical data regarding FB edits quality by sampling random edits. As software would need a bit more work to be suitable for open public access, I just sent out the link to the participants of our meeting as we there also discussed about the specific problems. Directly contact me if you are also interested.
Hope we can come up in a week or two with some statistics about how frequently bad tagging is.

Side-note: we said to focus on ways created by Facebook. Falsely changing existing tags as outlined above by Tom would not be caught.

I am looking forward to Stephan’s software, thanks. But I do have to gripe about his unfair choice of words.

No where in my post do I advocate doing anything ‘falsely’. I have fixed lots of FB roads for as long as they have been around. Usually I remove the tag ‘import’, as Stephan said to do. This is called ‘editing’.

The point of my post seems clear to me. I ask FB if they will consider doing some QA by reviewing their imports (just like we are planning with Stephan’s software). And it in fact is easier to fix a problem than to write a comment.

Just to avoid expectations we can’t fulfill: we plan to create statistics about the rate of tagging problems severely harming routing.

I would say a rate of one or more per hundred ways is certainly too much. Maybe we have to be even stricter.

Initial feedback is coming in. Ways first added as unclassified and later deleted again by Facebook seem to cause confusion.

I have been fairly uninvolved with mapping in Thailand since the FB team began their work so I’ve tended to minimize the bad and accentuate the positive up to now. In checking out some of the areas Stephan had outlined for use with his FB-checking tool, I stumbled into a whole nest of awful mapping done by FB. I commented on three changesets and took screenshots to include with this post. The issue of road classification is separate from these observations. This is just about slipshod work, sloppy mapping.

I was appalled to see how many ways simply end and were left “dangling” even though it’s glaringly obvious that they continue and eventually intersect with another way. How a team whose implicit concern is to make routing easier, to make connections, as opposed to adding water features or landcover, could consider their work finished in this area is both puzzling and disturbing.

The screenshots use Stephan’s mappaint JOSM addon so the FB imports are clearly shown. I would be embarrassed to have mapped this area and left it in the condition you see in the screenshots. The approximate coordinates of the center of the photos are also given so you can navigate to the area yourself.

I left changeset comments asking about a few of the dangling ways in the screenshots. There were simply too many to enumerate and comment about individually.

Holy moly, what a mess! While I still don’t think reverting their work is the best way to resolve this problem, it’s going to take quite a while to fix all the loose ends they’ve left lying around.

[1] https://www.dropbox.com/s/um9hz50cscurmop/Dangling%20ends%20%2815.2929%2C%20104.8408%29.JPG?dl=0 (15.2895, 104.8728)
[2] https://www.dropbox.com/s/3q15xfyno6a3d7d/Dangling%20ends%20%2815.2929%2C%20104.8908%29.JPG?dl=0 (15.2929, 104.8908)
[3] https://www.dropbox.com/s/tzcrgi7d5ifwgop/Dangling%20ends%20%2815.2895%2C%20104.8728%29.JPG?dl=0
(15.2929, 104.8408)

Hi Dave,

I can give some context on what you are seeing here. We cut Thailand into squares for the import process so you will sometimes see hard edges like this. It can look ugly and incomplete but it is a temporary artifact of the process. We are two projects away from filling in this spot so you will see this resolved shortly.