jorisvandenbossche commented on code in PR #560: URL: https://github.com/apache/parquet-format/pull/560#discussion_r3028878514
########## Geospatial.md: ########## @@ -44,8 +44,57 @@ locations on Earth. The default CRS `OGC:CRS84` means that the geospatial features must be stored in the order of longitude/latitude based on the WGS84 datum. -Custom CRS can be specified by a string value. It is recommended to use an -identifier-based approach like [Spatial reference identifier][srid]. +Non-default CRS values are specified by any case insensitive string that uniquely identifies a coordinate reference system associated with this type. +To maximize interoperability, suggested (but not limited to) formats for CRS are: +* `authority:code` - where `authority` represents some well known authorities, and `code` is the code used by the authority to identify the CRS - examples are `OGC:CRS84`, `OGC:CRS83`, `OGC:CRS27`, `EPSG:4326`, `EPSG:3857`. See [https://spatialreference.org/](https://spatialreference.org/) for definitions of coordinate reference systems provided by some well known authorities. +* `srid:identifier` - A reference using a [Spatial reference identifier (SRID)](https://en.wikipedia.org/wiki/Spatial_reference_system#Identifier), where identifier is the numeric SRID value. For example: `SRID:0`. +* `projjson:table_property_name` - where `table_property_name` is a reference to a CRS definition in [PROJJSON](https://proj.org/en/stable/specifications/projjson.html), stored in a file level key/value metadata key or table property. +* `projjson` - A complete CRS definition embedded directly using the [PROJJSON](https://proj.org/en/stable/specifications/projjson.html) specification. Example for `OGC:CRS83`: Review Comment: I would personally be fine with removing that long example, because even at the end of the list, it breaks the flow of the full document because of the vertical screen estate it takes. IMO the link to the projjson specification is clear enough about what it is. And potentially could include a abbreviated example, like `{"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json";, "type": "GeographicCRS", "name": "NAD83 (CRS83)", "datum": { ....` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
