Map translation

[tbodt]

What would it take to support rendering the map in any language which has translations in OSM?

[tbodt]

I see planetiler has a default list of languages: https://github.com/onthegomap/planetiler/blob/169627dea9b024f4b64f53039c302778c1c273bf/planetiler-core/src/main/java/com/onthegomap/planetiler/Planetiler.java#L106. This unfortunately doesn't include the language I want to use. I can imagine including all the languages would mean significantly bigger tile files...

[hyperknot]

Luckily it's not related to planetiler and is very simple to achieve.

1. Download the JSON from the style you prefer, for example this JSON:
   https://tiles.openfreemap.org/styles/liberty

2. Do a search and replace for "name_en" with "name_de" or whichever you prefer. Upload the JSON somewhere and simply point your style to this JSON instead of the default ones.

A dynamic JS snippet which does this is the following:

for (const layer of style.layers) {
  if (!layer.layout) continue

  const textField = layer.layout['text-field']
  if (!textField) continue

  // highway numbers, etc.
  if (isEqual(textField, ['to-string', ['get', 'ref']])) continue

  const id = layer.id

  let separator
  if (id.includes('line') || id.includes('highway')) {
    separator = ' '
  } else {
    separator = '\n'
  }

  const parts = [
      ['get', `name_${langCode}`],
      ['get', `name:${langCode}`],
      ['get', 'name'],
  ]

  layer.layout['text-field'] = [
    'case',
    ['has', 'name:nonlatin'],
    ['concat', ['get', 'name:latin'], separator, ['get', 'name:nonlatin']],
    ['coalesce', ...parts],
  ]
}

[tbodt]

This works decently well, but there are two problems

• This way of fiddling with the style JSON seems very brittle, surely it would be best for there to be some way for the style to like include a variable which can be filled in at runtime with the correct language?
• It doesn't include every language that has data in OSM/wikidata. For example: Europe has names in 82 languages on OSM, and 343 on Wikidata, but if you download and parse the PBF file for 0/0/0 you only find 76...and somehow a bunch of these 76 are not on OSM? how did that happen

[hyperknot]

This is basically the official solution. Actually the official solution is way more basic, I've spent a lot of time polishing it till I got to the version I posted. Have a look at the official example:
https://maplibre.org/maplibre-gl-js/docs/examples/language-switch/

About fiddling with JSON, basically all Mapbox/Maplibre styles are just that, JSON. I might set up a nginx function for this, but at the end of the day it'll just be a JSON with strings.

Now, about the mismatch of between OSM and OpenMapTiles, it's outside the scope of this project. You can see what's exactly in the data by going to the inspector mode of Maputnik:
https://maputnik.github.io/editor?style=https://tiles.openfreemap.org/styles/bright

[tbodt]

Thanks for the link to maputnik, it's definitely easier to use than manually deserializing pbfs.

What I don't understand, though, is the difference between OSM and OpenMapTiles, and why they would get out of sync. AIUI this project, OpenFreeMap, runs Planetiler, and then Planetiler fetches its data from OSM to generate all the tiles. Where does OpenMapTiles come in? What actually is OpenMapTiles?

[hyperknot]

Wrote a document for debugging international names:
https://github.com/hyperknot/openfreemap/blob/main/docs/debugging_names.md

[tbodt]

Turns out the list of languages in OpenMapTiles is equivalent to the list of languages in OpenFreeMaps, so that explains where it's coming from. What I don't understand is, why does planetiler use OpenMapTiles and not OSM directly?

[tbodt]

Oh there it is. https://github.com/openmaptiles/planetiler-openmaptiles/blob/5a07ce4ca7593622207cdf8f8330d52d31de8150/src/main/java/org/openmaptiles/generated/OpenMapTilesSchema.java#L62

[tbodt]

Would it be feasible to simply include all languages with data in wikidata in the tileset, or would that cost too much disk space?

[hyperknot]

So for your questions:

Why does planetiler use OpenMapTiles and not OSM directly?

Because OSM is just a database dump, it's not usable on it's own. You need to make a schema which can later describe geometries in the vector tiles. One such schema is OpenMapTiles. Other is https://shortbread-tiles.org/

Would it be feasible to simply include all languages with data in wikidata in the tileset, or would that cost too much disk space?

I don't know the answer for this, you should ask it in the Planetiler repo.

[tbodt]

Makes sense. Going to figure out what would need to change in Planetiler.

[hyperknot]

I've opened a ticket to render a full planet on the other two OpenMapTiles, so we can compare their implementation. This way we can see if something is planetiler specific, or is present in the other two implementation as well.
#25

[tbodt]

My assessment is:

• OpenMapTiles reference implementation has a list of languages defined in openmaptiles.yaml, and a surprising amount of dependencies on that list (e.g. using it to generate a list of columns for SQL statements) that would seem to make it hard to convince it to fetch labels for all languages.
• tilemaker just doesn't fetch labels in any other language by default, and has no support for wikidata - doesn't seem very useful without significant work.
• Planetiler's default task is to run with a configuration that matches OMT reference as closely as possible, apparently implemented as a Java file autogenerated from the aforementioned openmaptiles.yaml, thus inheriting the list of languages. There's no flag that will make it include all languages. But this is implemented by first fetching all labels for all languages from OSM and Wikidata, then filtering them - so it would be easy to make it just not, modulo bikeshedding over command line flags.

I'm currently looking into the feasibility of these Planetiler changes, hopefully I'll be able to do a full planet run to test the difference in output size.

[hyperknot]

Sounds great, thank you for digging into this!

These are the command line options I'm using for planetiler on a 128 GB machine. It takes about 5 hours to run:

openfreemap/modules/tile_gen/tile_gen_lib/planetiler.py

Lines 35 to 55 in f8f46a3

	command = [
	'java',
	f'-Xmx{java_memory_gb}g',
	'-jar',
	config.planetiler_path,
	f'--area={area}',
	'--download',
	'--download-threads=10',
	'--download-chunk-size-mb=1000',
	'--fetch-wikidata',
	'--output=tiles.mbtiles',
	'--storage=mmap',
	'--force',
	]
	if area == 'planet':
	command.append('--nodemap-type=array')
	command.append('--bounds=planet')
	if area == 'monaco':
	command.append('--nodemap-type=sortedtable')

[tbodt]

Looks like I can do a run on my 8GB machine in about 20 hours. Surprisingly this is fast enough for me for the moment since I have other things to do.

[tbodt]

So, the planetiler output without the language filter is about 2GB larger.

-rw-r--r--  1 tbodt  staff  93248712704 Oct  3 11:26 data/planet-all-langs.mbtiles
-rw-r--r--  1 tbodt  staff  91267948544 Oct  1 04:15 data/planet-osm-langs.mbtiles

I think this is worth it, what do you think? I'll work on the pull request for planetiler soon.

[hyperknot]

That's a great work, thank you! I think definitely open a PR in Planetiler and let them decide.

But before that, I'd make a very clear example of before-after for a few items, to understand what's missing from the old version.

[tbodt]

In onthegomap/planetiler#1043 they've said that it would make sense to have a flag, but they wouldn't make it the default since the default should match OMT as closely as possible. The question for you is whether you would set this flag for OFM.

I can post some before/afters here for you if you like.

[hyperknot]

Yes please. I mean especially include languages which you believe should be included. I'm not sure the right choice is to have hundreds of languages if no one would use them.

Also, could you compare the size totals of 4-6 tiles which are normally loaded for some popular view, say London or New York? I'm afraid that the 2 GB of size growth isn't distributed evenly, where every tile is 2% bigger, but some popular areas being 10-15% bigger, but it's just a guess from my side.

[tbodt]

I believe we should include every language indiscriminately - if a language has data, that means someone cared enough about it to type in labels.

[hyperknot]

Before making a decision, I'd be curious about other map platforms choice is on this.

[hyperknot]

Maptiler offers these languages:

1. English
2. Local
3. Albanian
4. Amharic
5. Arabic
6. Armenian
7. Azerbaijani
8. Basque
9. Belarusian
10. Bengali
11. Bosnian
12. Breton
13. Bulgarian
14. Catalan
15. Chinese
16. Corsican
17. Croatian
18. Czech
19. Danish
20. Dutch
21. English (listed twice)
22. Esperanto
23. Estonian
24. Finnish
25. French
26. Georgian
27. German
28. Greek
29. Hebrew
30. Hindi
31. Hungarian
32. Icelandic
33. Indonesian
34. Irish
35. Italian
36. Japanese
37. Japanese (Kana)
38. Japanese (Latin 2018)
39. Japanese (Latin)
40. Japanese Hiragana form
41. Kannada
42. Kazakh
43. Korean
44. Korean (Latin)
45. Kurdish
46. Latin
47. Latvian
48. Lithuanian
49. Luxembourgish
50. Macedonian
51. Malayalam
52. Maltese
53. Norwegian
54. Occitan
55. Polish
56. Portuguese
57. Romania
58. Romansh
59. Russian
60. Scottish Gaelic
61. Serbian (Cyrillic)
62. Serbian (Latin)
63. Slovak
64. Slovene
65. Spanish
66. Swedish
67. Tamil
68. Telugu
69. Thai
70. Turkish
71. Ukrainian
72. Vietnamese
73. Welsh
74. Western Frisian

[tbodt]

A list of maps with localization is at https://wiki.openstreetmap.org/wiki/Map_internationalization. Of those my language "tok" is only supported by Wikimedia maps, which seems to include every language indiscriminately, but the terms of use allow use only for Wikimedia projects.

[ImreSamu]

Although there are thousands of unique name: tags in OpenStreetMap (OSM),
many of them do not match the correct language code definitions.
https://taginfo.openstreetmap.org/search?q=name%3A#keys

Wikimedia recognizes around 710 language codes ( https://www.wikidata.org/wiki/Help:Wikimedia_language_codes/lists/all ), so ideally, this number of languages should be included to ensure all known languages are represented.
By clicking on the "WDQS" query, you can download the language codes in CSV format, which can be used after some cleaning.

• original WDQS : 730 result : https://w.wiki/63Z2
• only the distinct language codes : 710 result https://w.wiki/BQud -> RUN + Download CSV

name:tok - "Toki Pona"

@tbodt :

my language "tok" is only supported by Wikimedia maps,
which seems to include every language indiscriminately, but the terms of use allow use only for Wikimedia projects.

name:tok ( https://en.wikipedia.org/wiki/Toki_Pona )
Has only 323 objects in the OpenStreetMap : https://taginfo.openstreetmap.org/keys/name%3Atok#overview

The hard part is - creating a perfect map with 'Sitelen Pona' labels won't be easy due to the ~120 hieroglyphic characters.

• so need a special font set : https://jan-ne.github.io/tp/sp
• and transliteration will be needed. ( https://github.com/realjhoo/toki-pona-transliterator )

Transliteration isn't straightforward, as many non-Latin scripts (Arabic, Chinese, Japanese, Hebrew, etc.) first need to be converted into Latin characters before the Toki Pona transliteration can work.

[tbodt]

Happily, transliteration to sitelen pona is not really necessary. Latin script is more commonly used for toki pona anyway, so I would be happy with that on the map. If toki pona with sitelen pona was an option it would be its own language code with its own labels defined, just like how there are multiple language codes for Japanese. Automatically transliterating everything is not really worth doing.

[hyperknot]

Thank you for the research @ImreSamu. I thought about this and would like to choose the following decision forward:

• I'd like to stick with OpenMapTiles decisions for default languages
• But if there is individual need for adding a single language, I'm happy to include "tok" for example.

@tbodt if you submit a PR to planetiler to add individual languages and not all, then I'm happy to include "tok" in OpenFreeMap.

For your proposal of including all languages, why don't you convert your render to PMTiles and host that on Cloudflare? I mean, you can make an EveryLanguageMap or similar, I think it'd be a very interesting project!