Skycultures: Add country outline polygons

[gzotti]

Description

Skycultures 2.0 include polygonal descriptions for cultural regions in form of GeoJSON polygons. These can be created in the SCM plugin or in GIS applications like QGIS. The Stellarium-specific data are described in the User Guide.

Free data file for country borders are available, e.g. https://r2.datahub.io/clvyjaryy0000la0cxieg4o8o/main/raw/data/countries.geojson, from which borders of single countries can be extracted.

21st century country borders are generally not ideal as cultural borders often differ from national borders. Still, it's better than nothing.

Reading the big file we can see the Multipolygon geometry type. It would be great if this can be added to the acceptable JSON types. (EDIT: DONE)

Fixes # (issue)

Screenshots (if appropriate):

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update
• Housekeeping

How Has This Been Tested?

Test Configuration:

• Operating system: Windows 11
• Graphics Card: Any

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (header file)
• I have updated the respective chapter in the Stellarium User Guide
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching src/**/*.cpp:

• Are possibly unused includes removed?

Files matching skycultures/**:

• Did you remember to update skycultures/CMakeLists.txt file respectively to changes in sky cultures?
• Did you remember to define classification parameter in sky cultures (see index.json file)?
• Did you remember to define license parameter in sky cultures (see description.md file)?
• Did you remember to define region parameter in sky culture (see index.json file)?

This is an automatically generated QA checklist based on modified files.

[gzotti]

@sushoff I have added the MultiPolygon GeoJSON datatype and several country border polygons from existing free geodata as indicated. Greek/Almagest is obviously incomplete, would require "the Hellenistic world": either add all modern countries or define own polygon. Also for the other Greek/* (Leiden etc.). For various islands I have added the countries to which the islands belong today. This may be OK or not. Bali must be extracted from the Indonesia MultiPolygon (EDIT: Done).

[gzotti]

It seems @sushoff has no time to add a few polygons before 26.2. In 26.2 we can still have the functionality (Multipolygon in GeoJSON) and outlines for many Asian countries and islands. It would bring life to the map, and maybe first feedback for 26.3.

[gzotti]

@alex-w @10110111 any comments? IMO this state can go into 26.2, more territory files hopefully coming later this year.

[10110111]

Why are different parts of the same SC's region prelit separately? E.g. Honshu is prelit separately from Hokkaido while representing the same Japanese Yasui Map SC. Or North and South Koreas are prelit separately while representing the same Korean SC.

[gzotti]

The highlight is triggered by defined polygon, and I just copied N and S Korea Multipolygons from the file given above. For both areas I defined years 1500 to "today" (special code), and I expect some SC expert to fix the years. Same is true for some regional inner-China SCs. Also, all Multipolygons are split into series of Polygons which highlight separately by mouse-over. The tooltip shows the name of the skyculture, though, so this should not hurt too much.

[alex-w]

Acceptable for public testing, but it has mistakes in the data (modern vs. old borders)

[10110111]

OK, I guess it's acceptable, though the separate highlighting should be fixed at some point, because it makes no sense from the user's PoV.

…

On Sun, 14 Jun 2026, 16:22 Alexander V. Wolf, ***@***.***> wrote: ***@***.**** approved this pull request. Acceptable for public testing, but it has mistakes in the data (modern vs. old borders) — Reply to this email directly, view it on GitHub <#4919?email_source=notifications&email_token=ABQU3MVSLVLAAZD56WO5JWT47ZOENA5CNFSNUABKM5UWIORPF5TWS5BNNB2WEL2QOVWGYUTFOF2WK43UKJSXM2LFO4XTINBZGI3DGMZZGQ3KM4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#pullrequestreview-4492633946>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABQU3MX2U5I7QX2CAG6YXWT47ZOENAVCNFSNUABEKJSXA33TNF2G64TZHMYTQNZRHE4DKNR3JFZXG5LFHM2DINJWGQ3TGOBRG2QXMAQ> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/ABQU3MWGXHFV5N7UKX6GX5347ZOENA5CNFSNUABKM5UWIORPF5TWS5BNNB2WEL2QOVWGYUTFOF2WK43UKJSXM2LFO4XTINBZGI3DGMZZGQ3KM4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJKTGN5XXIZLSL5UW64Y> and Android <https://github.com/notifications/mobile/android/ABQU3MSAPMBXFN2BXOJD5LD47ZOENA5CNFSNUABKM5UWIORPF5TWS5BNNB2WEL2QOVWGYUTFOF2WK43UKJSXM2LFO4XTINBZGI3DGMZZGQ3KM4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLTGN5XXIZLSL5QW4ZDSN5UWI>. Download it today! You are receiving this because you were mentioned.Message ID: ***@***.***>

[gzotti]

I am pretty sure Chinese regional borders can be amended from the present copies of modern borders, by our Chinese experts who will hopefully provide cultural polygons with correct date range. Also: Does "Indian" SC also include other territories? I leave this fix to experts in Indian SC. But something has to be shown for discussion.

[gzotti]

OK, I guess it's acceptable, though the separate highlighting should be fixed at some point, because it makes no sense from the user's PoV.

OK, I take this as issue request for future development.

[sushoff]

I am pretty sure Chinese regional borders can be amended from the present copies of modern borders, by our Chinese experts who will hopefully provide cultural polygons with correct date range. Also: Does "Indian" SC also include other territories? I leave this fix to experts in Indian SC. But something has to be shown for discussion.

I am currently working on this - "Indian" is actually nakshatras and they started from the Indus Culture in the 2nd mill. BCE and extend to global use today (in new age philosophy)

I also did the two Babylonian geojsons and am currently working on the Greek / Greco-Egyptian ones - all this to be done today

[sushoff]

• Babylonian MUL.APIN (-1500 to -60)
• Babylonian Seleucid (-320 to -30)
• Indian Nakshatra
• Egyptian Dendera (Ptolemean)
• Greek Almagest (Roman)
• Greek Alm-Farnese (Roman-Levante)
• Greek Dante (IT 1300)
• Greek Leiden (Roman-Medieval)

remark: reworked Seleucid, and then let "MUL.APIN" end in 321 to avoid temporal overlap and make polygons better clickable (one after the other appearing when timeslider moved)

[sushoff]

We (with the Chinese colleagues) consciously decided to postpone for Sept.

• 12. chinese 
• 13. chinese_chenzhuo 
• 14. chinese_manchu 
• 15. chinese_song_dynasty 
• 16. chinese_xianglin 
• 17. chinese_yuan_dynasty 

... and to skip those from Digitalis Education Solutions, Inc.

• 18.  egyptian 
• 45. navajo 
• 25. inuit 

We now have

• 1. anutan 
• 2. arabic_al-sufi 
• 3. arabic_arabian_peninsula 
• 4. arabic_indigenous 
• 5. armintxe 
• 6. aztec 
• 7.  babylonian_mulapin 
• 8. babylonian_seleucid 
• 9. balinese 
• 10. belarusian 
• 11. boorong 
• 19. egyptian_dendera 
• 20. greek_almagest 
• 21. greek_dante 
• 22. greek_farnese 
• 23. greek_leidenAratea 
• 24. hawaiian_starlines 
• 26. indian 
• 27. indian_nakshatras 
• 28. japanese 
• 29. kamilaroi 
• 30. khoi-san 
• 31. korean 
• 32. lokono 
• 33. macedonian 
• 34. maori 
• 35. maya 
• 36. modern 
• 37. modern_chinese 
• 38. modern_rey 
• 39. modern_iau 
• 40. modern_hlad 
• 41. modern_st 
• 42. modern_journey_to_the_west 
• 43. modern_sternenkarten 
• 44. mongolian 
• 46. norse 
• 47. norse_edda 
• 48. northern_andes 
• 49. romanian 
• 50. ruanui_sky_tahiti_and_society_islands 
• 51. russian_siberian 
• 52. sami 
• 53. samoan 
• 54. sardinian 
• 55. seri 
• 56. tibetan 
• 57. tongan 
• 58. tukano 
• 59. tikuna 
• 60. tupi 
• 61. vanuatu_netwar 
• 62. xhosa 
• 63. zulu 

[10110111]

We (with the Chinese colleagues) consciously decided to postpone for Sept.

And what about #4994?