SOIUSA code

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title: "SOIUSA code" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["alps", "encodings"] topic_path: "general/alps" source: "https://en.wikipedia.org/wiki/SOIUSA_code" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

Main article: SOIUSA

SOIUSA code is the code used in the International Standardized Mountain Subdivision of the Alps (ISMSA or SOIUSA), a proposal by Italian Alpinist, Sergio Marazzi, to re-categorize the mountains and mountain ranges of the Alps. The proposal has been aired since 2005 but has yet to receive official recognition.

SOIUSA groups' hierarchy

::figure[src="https://upload.wikimedia.org/wikipedia/commons/5/50/Pyramid_soiusa_eng.png" caption="SOIUSA pyramid showing its groups' hierarchy."] ::

SOIUSA divides the Alps in two main regions, the Western Alps and Eastern Alps. These two main regions are further divided in:

• 5 major sectors (SR);
• 36 sections (SZ);
• 132 subsections (STS);
• 333 supergroups (SPG);
• 870 groups (GR);
• 1625 subgroups (STG).

Using this system, any Alpine mountain can be given a code which shows which region, sector, section, subsection, supergroup, group and subgroup it belongs to.

Encoding

SOIUSA code is built in the following way:

• 2 main parts:
  • Western Alps are identified by roman numeral I;
  • Eastern Alps are identified by roman numeral II;
• 5 major sectors:
  • in Western Alps:
    • South-western Alps are identified by upper-case letter A;
    • North-western Alps are identified by upper-case letter B;
  • in Eastern Alps:
    • Central Eastern Alps are identified by upper-case letter A;
    • Northern Limestone Alps are identified by upper-case letter B;
    • Southern Limestone Alps are identified by lower-case letter C;
• 36 sections: identified by numbers from 1 to 36 starting from Ligurian Alps and ending with Slovenian prealps;
• 132 subsections: identified in their own section by the roman numerals needed to count every subsection;
• 333 supergroups: identified in their own subsection by all the upper-case letters needed to count every supergroup;
• 870 groups: identified in their own supergroup by all the numbers needed to count every group;
• 1625 subgroups: identified in their own group by all the lower-case letters needed to count every subgroup.

Following these rules and using the punctuation marks (/; -; .; -; . and .) a summit will be encoded in the following way:

roman numeral (I or II) / upper-case letter (A, B or C) - number from 1 to 36 . roman numeral - upper-case letter . number . lower-case letter

In some case the final lower-case letter can be missing because some group is not divided into subgroups.

It can seldom happen (i.e.:Monte Tagliaferro) that a subgroup too is further divided in sectors; in that case the last lower-case letter is followed by a slash (/) and a second lower-case letter.

Encoding example

|title=SOIUSA parameters of pointe Sommeiller (Fr) / punta Sommeiller (It) |content=

• main part = Western Alps
• major sector = South Western Alps
• section = Cottian Alps
• subsection = Northern Cottian Alps
• supergroup = chaîne Bernaude-Pierre Menue-Ambin (Fr) / catena Bernauda-Pierre Menue-Ambin (It)
• group = groupe d'Ambin (Fr) / gruppo d'Ambin (It)
• subgroup = crête Sommeiller-Vallonetto (Fr) / sottogruppo Sommeiller-Vallonetto (It)
• code = I/A-4.III-B.6.b |col3=Black
  |col1=lightblue |col2=white}}

Pointe Sommeiller (Fr) / Punta Sommeiller (It) code is:

** I/A-4.III-B.6.b**

It can be decoded in the following way:

• I: the mountain belongs to Western Alps,
• A: the mountain belongs to South Western Alps,
• 4: the mountain belongs to Cottian Alps,
• III: the mountain belongs to Northern Cottian Alps (which are the third out of three subsections belonging to Cottian Alps),
• B: the mountain belongs to chaîne Bernaude-Pierre Menue-Ambin (Fr) / catena Bernauda-Pierre Menue-Ambin (It) (which is the second out of two supergroups belonging to Northern Cottian Alps),
• 6: the mountain belongs to groupe d'Ambin (Fr) / gruppo d'Ambin (It) (which is the sixth out of six groups belonging to Bernaude-Pierre Menue-Ambin supergroup),
• b: the mountain belongs to a subgroup called crête Sommeiller-Vallonetto (Fr) / sottogruppo Sommeiller-Vallonetto (It) (which is the second out of three subgroups belonging to Ambin group).

References

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