Proposal:Boundary=cadastral

Boundary=cadastral
Proposal status:	Draft (under way)
Proposed by:	Biff
Tagging:	boundary=cadastral Data item
Applies to:
Definition:	Tagging scheme for cadastral boundaries
Statistics:
Rendered as:	TBD
Draft started:	2023-05-12

Proposal

A cadastral boundary delimits a cadastral district, a cadastral section or a cadastral plot. These cadastral divisions do not have an administrative role in the sense intended for tagging with boundary=administrative.

Rationale

In several places, the tag is already being used, see taginfo and examples below. It would be good to document the preferred way of using the tag, to provide clear guidance to users who wish to add cadastral information to the database.

However, users should consider that OSM does not aim to be a land registry. Cadastral information should not be added simply because it is available. The information should have some relevance for OSM. For example, sometimes the cadastral boundaries establish the boundaries of a locality, which would otherwise be difficult to define.

See also Parcel.

Tagging

In some cases, the cadastral boundaries are visibly marked by boundary stones, in other cases information about them is available from cadastral records, which in some countries are available under a license that is compatible with OSM.

Tag	Element	Comments
type=boundary		Type of relation (if a relation is used).
boundary=cadastral		A tag for cadastral limits and relations.
cadastral_level=*		A tag to describe the level of the cadastral division, related to admin_level=*, see details below.
name=*		The name of the cadastral unit.
ref=*		The reference code (id number) assigned to the cadastral division by the cadaster.
source=*		Source information, see also Talk:Parcel#Verifiability. Possibly combined with check_date:source=* or survey:date=*.

For mapping of physical markers in the corners or other parts of the boundary, see boundary=marker and marker=*. Source information should be given as described above for the boundary.

cadastral_level

Application of the number values of admin_level=* to cadastral divisions might be difficult. For example, in Germany the cadastral districts are assigned and numbered by each federal state, although even the highest level of cadastral division is frequently smaller than a town. Also, equal values for admin_level=* and cadastral_level=* could provide the impression to users that they are of similar size, which is not always true.

Country (cadastral_level=2)	cadastral_level=*
	3	4	5	6	7	8	9	10	11	12
Germany	N/A	federal states border (Bundesland)	N/A	N/A	N/A	N/A	N/A	Gemarkung	Flur	Flurstück

Therefore, it might be better to use named values:

Country	cadastral_level=*
	Cadastral district	Cadastral section	Cadastral plot
Germany	DE:Gemarkung	DE:Flur	DE:Flurstueck

Of course, this will make it difficult to render cadastral boundaries consistently among countries, but the mapping between named levels and corresponding line styles can probably be done later, when the scheme has been applied to a sufficient number of countries.

Examples

Apparently, the boundaries of all land districts of British Columbia in Canada have been tagged with boundary=cadastral, for example https://www.openstreetmap.org/relation/11542596 .

In Germany, several Gemarkungen are currently tagged using boundary=administrative. These should be changed to the boundary=cadastral scheme.

Some parcels have been mapped using boundary=cadastre, most of them in Australia, see https://taginfo.openstreetmap.org/tags/?key=boundary&value=cadastre#overview. These should be changed to the boundary=cadastral scheme.

Rendering

Cadastral boundaries can be rendered in a similar manner as administrative boundaries, using a different color or a different dashed or dotted style of the border line.

Features/Pages affected

boundary=* and boundary=administrative should be edited to point to boundary=cadastral.

Comments

Please comment on the discussion page.