rdblue commented on code in PR #15834: URL: https://github.com/apache/iceberg/pull/15834#discussion_r3169512254
########## format/spec.md: ########## @@ -242,10 +242,13 @@ For `geometry` type, the CRS does not affect geometric calculations, which are a The default CRS value `OGC:CRS84` means that the objects must be stored in longitude, latitude based on the WGS84 datum. -Custom CRS values can be specified by a string of the format `type:identifier`, where `type` is one of the following values: +Non-default CRS values are specified by any string that uniquely identifies a coordinate reference system associated with this type. +To maximize interoperability, suggested formats for CRS include, but are not limited to: +* `<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`, `IGNF:ATI`. See [https://spatialreference.org/](https://spatialreference.org/) for definitions of coordinate reference systems provided by some well known authorities. +* `projjson:<property-name>` - where <property-name> refers to a table property where CRS definition in [PROJJSON](https://proj.org/en/stable/specifications/projjson.html) format is stored. +* `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`. -* `srid`: [Spatial reference identifier](https://en.wikipedia.org/wiki/Spatial_reference_system#Identifier), `identifier` is the SRID itself. -* `projjson`: [PROJJSON](https://proj.org/en/stable/specifications/projjson.html), `identifier` is the name of a table property where the projjson string is stored. +CRS value must not contain inlined PROJJSON definitions and implementations must not parse the contents of the CRS as PROJJSON. If intention is for PROJJSON definition to be part of the table metadata, then it must be stored in a table property and referenced from the CRS field using the `projjson:<table_property_name>` form described above. Review Comment: 🚀 -- 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]
