Lakkavokka is a JOSM plugin for digitizing indexed color images in a controlled manner. This tool is useful for semi-automated imports in ML/AI mapping pipelines.

Usage

The following steps requires you have JSOM ext_tools plugin installed.

0. Make sure you have Python >3.8 and Pip installed:

$ python3 --version
Python 3.8.10

$ python3 -m pip --version
pip 20.0.2 from /usr/lib/python3/dist-packages/pip (python 3.8)

1. Install Lakkavokka:

python3 -m pip install lakkavokka

2. Setup external script in JOSM

Use Lakkavokka as a name and lakkavokka --lat {lat} --lon {lon} --zoom 16 --source /path/to/tiles/{zoom}/{x}/{y}.png as a command line.

Now, you can open your area in JOSM, enable Lakkavokka tool and click on the map. Lakkavokka will load the area around the clicked point and build a way nearest to the point. It doesn't matter if you click inside or outside the colored area. If the area is small enough, the way will be automatically closed. Otherwise, you can combine those line to the multipolygon later.

Command line options

--source TMS tiles source, can be either a file path template or URL template. Variables {zoom}, {x}, and {y} will be automatically substituted to tile coordinates

--buffer number of tiles around the clicked point to be loaded. Increasing this value will significantly increase required RAM and calculation time. You can adjust this setting according to your data. Most useful values are from 1 (default) to 3.

--simplify-factor simplification factor for the resulting geometry. You should adjust this setting according to your data if you're getting too many points or too coarse geometry.

--tags comma-separated list of tags to be added to generated ways. It's a good idea to add source tag to indicate other mappers that is an automated or semi-automated load of data.

--lat and --lon latitude and longitude of a clicked point

--zoom zoom of tiles will be processed. It may be different from the zoom level in JOSM but it should always match the best zoom of tiles.

Example workflow

1. Download data/8323903.tar.gz from this repository. This file contains forest overlay for a random rural area in Bashkortostan republic, Russia.
2. Extract this file somewhere
3. Enter the 8323903 directory and run python3 -m http.server 9000 you could skip this step and point --source parameter to the directory itself, but it is more convenient to be able to see the data in JOSM
4. Open JOSM and add image layer, type TMS, URL tms[16,16]:http://localhost:9000/{z}/{x}/{y}.png
5. Download area around https://www.openstreetmap.org/#map=14/52.3410/57.8839 in JOSM and enable recently added layer
6. Setup lakkavokka as described earlier. If you're using http.server you can omit --source parameter.