OpenStreetMap

Newbie mapper's whining, joy and fear

Posted by kanoalgiz on 29 June 2022 in English (English). Last updated on 30 June 2022.

{Insert standard apology about poor english from non-native speaker here}

So, I've found this beautiful thing, the OSM, I'm feeling so inspired and motivated - finally a platform where I can make contribution and fixes knowing that my efforts will not be in vain!

I'm currently living in Gyumri, Armenia, and maps here... have issues. On Google Maps, seems that building were autogenerated from satellite images - there are obvious errors, missing buildings, nonexistent buildings, buildings with weird geometry, buildings that are crossing roads or each other, roads that in reality are footpaths, footpaths that are ending abruptly (because they are partly hidden by trees on satellite image) - you name it. Addresses are absent on 90% of buildings. In my city, all you can do in Google Maps - 'add missing place' or 'add missing address' ('fix road' option in my area is not available), by filling some form and hope that it will be accepted by somebody someday. But where should I add address if the building itself is not present on the map!?

At least Google is accepting edits related to places (working hours, changed location etc.) pretty fast usually. In case of Yandex Maps that is not the case. Those were my favorite maps (especially UI-wise) before... before I've tried to start contributing and fix errors about ogranizations I visit. Seems that in vast majority of edits you will receive seemingly automatic "Unfortunately we were unable to confirm" letter. "We need more information to confirm the edit. Please contact support." What? Why? Oh well... After writing to support, they usually do add edits without any additional questions. - "Why did you reject same edits in the first place? That is looking almost automatical. Are you defending from bots that way? What did I do wrong and how can I do edits 'the right way' in the future to avoid bothering you and wasting time of support specialists?" - "Sorry, we do not disclose details of our verification processes. Please be understanding.". That's demotivating. If I'm adding a photo of some shop that have none of them - it can wait for a 'verification' for a month or more. I'm still waiting! Photos usually greatly help me to navigate in new places...

After that, OSM feels like a breathe of fresh air, like a knight on a white horse (haha, sorry) that should free me from that corporate bureaucracy and finally allow me to do useful stuff for free! (lol)

Though that's a pity that by making changes on OSM I cannot enhance my experience with sites and services that rely on other maps (for some food delivery services you cannot even pick your location if your house's address is not on a map - and you're lucky if it allowes to type in any address without validation). I really hope that more and more businesses will rely on OSM's data in the future.
And, though I'm annoyed by Yandex & Google - honestly, currently I do not see real alternatives when I use maps to search for some organization or just find a nice place to have a lunch - I really rely on photos, ratings, user's feedbacks and a flexible search by name and organization type... (at least, I used that on a daily basis when I was living in a big city, where most organizations are on map and data is usually relevant). In that sense, OSM is clearly deeply map-centric, businesses are not in its focus, I understand that. I can recommend it to my friends to search for an address, not for 'fish restaurant'.
Of course, there are apps like 'Maps.me', that do use OSM data and seem more average-user-friendly, but in my place they are not so popular, almost unknown, so quality and comleteness of data that should be added by users suffers, comparing to mainstream map services. I haven't tried to add data using mapbox UI yet myself, that's for the nearest future =) But looks nice already! I wonder if they do some 'validation' and how long it is...

As I opened Gyumri map after completing OSM's marvelous crash course, I've noticed bunch of inconsistencies in my district - and, while clarifying buildings geometry, naively shifted those buildings 'to match the image'. Only after some time I noticed that you can choose between different background image sources. With different shift relative to data layer. Stupid me... but what is the right way? Quite quickly I found the answer on the wiki (Error Categories). In Gyumri, GPS data is... scarce. And I have no car. I checked different parts of the city (which is more or less flat as I know) trying to find offsets what make existing paths lay on roads as nicely as possible. For Bing imagery that appeared to be ~2.8, 4.2. Buildings still seemed off, but now I was modifying them with some amount of confidence - clearly, buildings were marked without gps data before, seemingly created using Esri-Clarity images without any shift. To double-check myself, today I switched to Esri, hid data layer, shifted Esri images to GPS tracks and then enabled data layer again to see buildings that I modified earlier. Well... not bad, I think, but not great either, with at least 2 meters shift. Sigh... But what if I shift Esri layer now, to match my moved buildings? I suppose, gps tracks will be looking misplaced then? No! They are still 'somewhat on roads', and that magic gives me anxiety. After all, seems that there are just not enough gps data to be sure. And now, after clarifying buildings and roads locations for a half of district (that turned out to be almost meditative process), I'm not sure even that what I do is right. Yes, at least it is closer to gps data than it was previously, but do I need to make those changes if in the future somebody may be using more complete gps data that may give other offsets? Or somebody decides to edit map of Gyumri now and finds different offsets because of scarcity of current gps data. In both cases it will be like re-doing the same work again. I don't know now if I should revert my own changes. After all, I did not make map less precise, and in case of geometry, it is definitely an upgrade. But.... that offsets stuff... ugh. Maybe I'm just missing something in my approach. I'm a newbie, after all. At least I will record gps tracks when using taxi now =)

Location: Ani district, Gyumri, Akhuryan region, Shirak Province, Armenia

Comment from Marcos Dione on 30 June 2022 at 07:53

From another non native speaker, your English is perfect :)

I have no car

Bicycle or kick scooter would be fine, the city does not look that big :)

if I shift Esri layer now, to match my moved buildings? I suppose, gps tracks will be looking misplaced then? No! They are still ‘somewhat on roads’, and that magic gives me anxiety

I think that’s expected. Tracks most probably are independent of imagery, that’s why you could consider tracks as ‘ground truth’ and align imagery based on that. At least, that’s the theory.

If you have more questions, I suggest you to join the #osm IRC channel at oftc.org and ask about these things; I’m not an expert on those myself.

I’m not sure even that what I do is right

As long as you think is the right data, please do. If later someone finds a better alignment, I think the data can be easily realigned. But again, better ask more knowledgeable people. IRC as I mentioned above (mostly synchronous, chat), or maybe the new site at https://community.openstreetmap.org/ (more async, forum).

Comment from kanoalgiz on 1 July 2022 at 09:58

Thank you for the links! Bike/scooter for recording tracks sounds nice, but, I suppose, only if I will using those tracks without uploading to OSM as public tracks. Here, cycling on roads is not so safe, people usually do that on walkways, so those tracks definitely will be shifted comparing to existing ones and can confuse OSM users if they think those were recorded on roads too =) I just thought that tracks from just one person should not be relied on (especially if all person can use is a smartphone gps) and all I can do is make a small contribution to available data - and, as the dataset grows, all tracks can be approximated and used as a reference. If that point of view is too modest - when, I think, I can even record when I travel by foot (which at least can help with my district, where almost all streets have 0 tracks). Thank you again!

Comment from pkoby on 1 July 2022 at 12:50

Something to try if you want to figure out the right offset.

  1. Download an app for GPS Averaging (search your app store, there should be a few options).
  2. Find a point that you can see on the aerial imagery, like a fire hydrant, manhole cover, lamp post, etc., ideally with a wide open view of the sky. Go to that place and get an average GPS reading (leave it for a minute or longer). Maybe even do it another day to get another reading to double-check. The GPS point should be in decimal degrees (e.g. N ##.#####, E ##.#####).
  3. In the iD editor, you can center on that location (change the URL to match the GPS point: https://www.openstreetmap.org/edit?editor=id#map=24/##.#####/##.#####).
  4. Drop a point in the middle of the editor.
  5. Zoom out a bit and then align your imagery of choice to line up the spot in the picture under your point.

If you do this for a few spots in town and they all have about the same offset, then you can confidently use that as your default. Good luck!

Comment from MxxCon on 1 July 2022 at 20:55

Many mobile apps have an ability to record GPS tracks. You could use those to record even your walks on the sidewalk and align to that. Depending on the quality of the available satellite imagery, 1-2meter precision could be as good as it gets.

Also consider contacting your local/regional government to find out if they have a GIS office who might share some address or buildings or other useful dataset with you.

Recruit your friends/classmates/coworkers to also start mapping with you 🙂 have them show pride of their city.

Regarding not being able to find an address on Google maps or other food delivery apps, consider trying Plus Codes. It’s a free positioning system that’s easier to remember than raw GPS coordinates. Google Maps and many OSM-based apps support it. For example try 8HG5QRPR+3J That might work instead of address.

Comment from Xvtn on 14 July 2022 at 17:54

After having the same initial gripes about imagery offsets I decided to bike every street in my city - for fun, for OSM accuracy, and to get in better shape. It’s been a lot of fun! Check it out! I think really any mode of travel - bike, car or transit can be useful to get some GPS traces put down. Some other users’ comments here point out some great tips as well.


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