Forest import


Any suggestion how to remove all those forest plots? I saw some perl scripts done by you, but I don’t know Perl.



So when are those forest plots removed? It is now nearly impossible to draw new roads, tracks, paths (in Potlatch) because they get connected to the borders of all those forest plots where a very thin line between them is left open (where the finnish national map shows a path).

You should consider using JOSM as editor for OSM. In JOSM you can disable “snap to line” by holding Crtl while placing a node.

I have been travelling quite recently. I haven’t got any feedback/help for deleting processes. So it seem obvious that I have to plan and excute it myself (and I’m willing to do it). However, it will take a little bit longer.

I have idea just remove all those forest plots which are imported by me. Unless someone has been edited those.


I appreciate your willingness to remove your edits. Unfortunately I cannot help you with that. Although maybe this particular large import did not work, I hope that you can find some other way of importing useful data, that will improve the map!

What is the current state about this? I have run into a lot of erroneous forests created by this import in my new neighborhood in Oulu and started cleaning them up, which requires a lot of fiddling around with multipolygons.

But after thinking about it again, I was wondering whether manual fixing is the right way here. Should I just leave these - although they interfere with other edits - so that they can be cleaned up automatically?


I need to prepare custom scripts to make reverts: existing tools will leave some features to database.

My plan is that those custom revert script won’t touch if somebody have been updated features. So, if you clean or modify those forest plots, I won’t revert (aka delete) those.


What is the update on this?


I have prepared Python scrit for reverting and tested it. If you like help me for testing (and further develop the script), I can share it. Or I can put into github repo or something.


github repo would be great, since then the algorithm itself could be discussed


Hi! :slight_smile:

I’m quite new at OSM and have read about this import yesterday. And I’d like to quickly point out a way how to use the data in a way which might be appreciated by the community. Sadly, I won’t have time to do this myself, so this is just supposed to be a quick idea for anyone interested.

Firstly, I agree that this whole import needs to be reverted because what you did, posiki, is overfitting of your data (

But in my opinion, such a large amount of data is a huge chance to improve OSM if it is used in the right way. Such an import should not cause any harmful interference with past or future edits of the community. After reverting the first import, you could follow these steps:

  1. Vectorization of the pixel forest data: Initial forest patches just as you did, posiki.

  2. Creation of new forest patches, only based on new points at the center of each line of the initial forest patches. Like this, you effectively average each two neighboring points. This eliminates most of the pixel structure without increasig the amount of points. And you avoid overfitting: You use a minimum amount of points to represent the forest shape at the accuracy of the underlying data set. This sows the accuracy of the data to future mappers and makes future improvements as easy as possible because they need to move only a few points for corrections.

  3. Only cut out highways of type tertiary and above. Like this, you avoid pseudo mapping of small roads and paths with small blank lines in the forest as you did before. Thus, future mappers won’t run into accidentally merging your forest points with their new highway points.

  4. Cut out all existing OSM areas except of forest with 3m buffer (buildings, landuse, lakes, sportsgrounds etc.). Cut out forest without buffer. Like this, you avoid sharing points with any existing OSM object except of forest. Thus, future mappers can change these without being bothered by freeing them from your forest.

  5. Deletion of all forest patches below 2300m². The LUKE data set’s pixels are sized 16m x 16m. So you should at least delete all patches below an area of 3x3 pixels, 48m x 48m, approx. 2300m² to avoid messy small forest patches.

  6. Test import and visual inspection at randomly chosen areas.

  7. Community Discussion. Adding additional image processing steps if needed.

  8. Full import.

In my opinion, OSM needs to welcome and professionaly process external data to keep up with e.g. AI based map services in the future. That’s why I want to thank you, posiki, for caring about importing this data. I hope I could help a little with this.



Just note: that this forest removal will happen in next following months. Some result can be seen already in

Again, sorry about all bad feelings what this forest import has done.



I will revert my forest import. And leave with rest of the community figure out what to do afterwards

ps. sorry to answer sooner on this…

I would like to say good job @posiki ! The algorithm i quite useful for creating data which then can be imported in parts by mappers.

I fully agree that this should be done manually and as long as the forest polygons focus on large enough forest, then I think it should be quite doable to import for people.

For example the norwegian N50 import started in 2014/2015 and is closing in on being finished now.

This data source is old, but still valid. So manual review is required to adjust stuff during import.

Another import we are doing in Norway is import/merging of 4.3 million buildings

  • 14 people have imported 50% of the data so far in the last 6 months, so large imports like these are fully doable, as long as the data is easily available in human manageable areas.

Some tips to make it easier to import and deal with for other people:

  • Reduce smoothing of edges → easier to deal with polygons for users coming into OSM
  • Is it required to stop the forest when you reach a road? I see no problem with letting the road run through the forests.
    → Continuous forest across highways makes it much easier to correct roads when better imagery arrives.
  • Focus on large forest areas first → Easier to review → Quickly adds the forest-look to the map.

Good luck! I hope you find a good method to do this in the finnish OSM community, maybe some of us from Norway could join in when the data is easily reviable and importable.