France boundary pyramidal construction
This page's aim is to explain how and why we have constructed the french boundaries in a pyramidal relation inclusion instead of multiple ways inside only one relation.
It is not incompatible with the "traditional method" explained here Relations/Proposed/Boundaries
- In the traditional method (only ways as members) editing became very hard due to the huge list of members
- Boundaries between two countries could be reused by the two relations forming the two countries/regions
- (Forming a boundary relation made of Relations/Proposed/boundary segment relations)
- Easier to represent or use the boundary between 2 countries/regions
I created a proposal for that described here Relations/Proposed/boundary_segment
Since France is spread all over the world (due to its past colonies), we have created different relations for different territories.
Main Territory (France + Corsica)
This relation contains the European part of France :
This relation contains the previous relation as a child member and every other extra-European territories (check the relation for the list)
- Both relations have tags :
- name + name:XY
- With child relations of Relations/Proposed/boundary segment if linear or type=boundary/multipolygon + boundary=administrative if forming a closed polygon.
it may contain single ways as well if there are few between one country and France (France / Monaco could have been represented by two ways only)
The sum of its ways, relation's ways and relation's relation's ways should form one or more closed polygon(s) that represent France's boundaries. (just like the Relation:multipolygon relations). It should not contain relation members that are administrative subdivisions (admin_level 3 or more). It means it shouldn't contain "inside" boundaries, just the outlines of France.
- Relations/Proposed/boundary segment are created in order to represent something meaningful and linear (i.e. France/Spain boundary, a coast with one sea...)
- They may contain other relations as well.
- Those relation are created to be used in multiple other relations :
- in the two neighbour countries
- in the multiple country relation such as territorial borders, water borders.
- Where to put enclaves of a country ?
- Enclaves should be child member of the boundary relation, not member of the boundary segment.
- Should the boundary relations only form one continuous line ?
- No. For exemple, in the case of the France/Spain boundary, Andorra is a country that cuts this boundary in two, anyway, those two lines are to be put in the same boundary segment relation (but they could be relations themself as well, but France and Spain will only have one "France/Spain" boundary and only one relation for that)
Don't delete the traditional non pyramidal relation
Please do not delete the "traditional method" boundary if you use the pyramidical construction, since mapmakers around the world rely on the consistency of the "traditional method" for the country boundaries they use worldwide.
- Unfortunately, this is easy to ask, but harder to do ! Technical limitations of the OSM editing servers makes it almost impossible (specially to non power users) to edit some huge relation made with the "traditional method". I guess the traditional relations should be kept as long as possible until data consumers update their software, but when editing become impossible, they will be dropped because my view is that editing has priority over consumers sletuffe 15:24, 5 May 2012 (BST)