Tried to use [http://polygons.openstreetmap.fr/index.py][1] but it doesnt seems working properly with inner rings. Eg. try to look at relation 62657, you will see that it generates WKT with 2 polygons, where both are outer. It can be easily checked here: [https://clydedacruz.github.io/openstreetmap-wkt-playground/][2].
So there is [web scraping service][3] with geo functionality, which has free tier so can be freely used for conversion. If you need to convert more than 5000 relations, you can compile scraper to run on your local computer / server without limitations. Below is a code for the scraper that do conversion job:
---
config:
debug: 2
agent: Chrome
iterator:
- type: csv
name: relation
value: "62657"
"62657,62554,62378"
do:
- geo:
do:
- wkt:
relation: <%relation%>
do:
- find:
path: wkt
do:
- object_new: item
- parse
- object_field_set:
object: item
field: wkt
- argument_get: relation
- object_field_set:
object: item
field: relation
- object_save:
name: item
There is nore geo functionality available, you can read [documentation][4]
[1]: http://polygons.openstreetmap.fr/index.py
[2]: https://clydedacruz.github.io/openstreetmap-wkt-playground/
[3]: https://www.diggernaut.com
[4]: https://www.diggernaut.com/dev/meta-language-methods-geospatial-data-working-with-geospatial-data.html
