Extending the GeoSPARQL ontology with support for M and T coordinates

[FransKnibbe]

Contributed by Timo Homburg for the white paper "Benefits of Representing Spatial Data using Semantic and Graph Technologies":

Many geospatial libraries such as JTS (https://github.com/locationtech/jts) provide explicit support for geometries with measurement (M) coordinates. These are useful in a variety of applications e.g. when a road is simplified in a query statement but users still would like to query the correct amount of kilometres since its start. The time coordinates (T) are useful when working with GNSS tracks in order to track per-point when a user went to a particular place. While the latter can also be achieved by modeling every point of a GNSS track as its own point geometry, it is unnecessary if the points provide no further semantic information apart from the time point. While the support XYZM or XYZMT coordinates is not a matter of GeoSPARQL itself but more of the formats which are supported as literals in the query language, GeoSPARQL could provide definitions of functions which are aware of these extended coordinate concepts such as:

• ST_M/ST_T
• ST_FilterByM/ST_FilterByT
• ST_PartOfGeometryBefore
• ST_PartOfGeometryAfter
• ST_PartOfGeometryAt

[situx]

Now available as a ticket http://ogc.standardstracker.org/show_request.cgi?id=630

[dr-shorthair]

Probably an overlap with Linear Referencing - https://www.iso.org/standard/32566.html (a.k.a. OGC Abstract Spec Topic 19)

[jabhay]

MoSCoW poll created

[VladimirAlexiev]

Is "EWKT" relevant here? (copied from https://github.com/BenzclyZhang/BimSPARQL/issues/2):

• https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Format_variations: "EWKT: A PostGIS-specific format that includes the spatial reference system identifier (SRID) and up to 4 ordinate values (XYZM).[4][5] It also supports circular curves, following elements named (but not fully defined) within the original WKT: CircularString, CompoundCurve, CurvePolygon and CompoundSurface.[6]

  • [4] https://github.com/postgis/postgis/blob/2.1.0/doc/ZMSgeoms.txt
  • [5] https://postgis.net/docs/ST_GeomFromEWKT.html : supports Polyhedral surfaces, Triangles and Triangulated Irregular Network Surfaces (TIN).
  • [6] https://postgis.net/docs/manual-1.4/ch04.html

• Does anyone know where is the authoritative documentation of this EWKT format?

• @dr-shorthair Does ISO 19148:2021 "Linear referencing" define a serialization format? Is it related to EWKT?

• @jabhay where is this poll?

[situx]

@VladimirAlexiev To my knowledge, EWKT is a PostGIS-specific format that mainly adds the SRID. I think SFA has caught up with XYZM coordinates at this point. Probably the only documentation is what you will find in the PostGIS documentation.

As for this issue: I think there was support for adding functions that would deal with M and T coordinates, with M coordinate functions akin to the PostGIS implementation. The poll is probably gone, given it is already more than two years old.

[VladimirAlexiev]

@dr-shorthair Proposed ontology for Linear Referencing: https://roadotl.eu/static/eurotl-ontologies/iso19148_doc/index-en.html

[VladimirAlexiev]

The EurOTL site is at https://wpd1.s3.eu-central-1.amazonaws.com/index.html: The proposed ontology is at https://wpd1.s3.eu-central-1.amazonaws.com/iso19148_doc/index-en.html. Please note that it has an external class in error, search for Error