milastdbx commented on code in PR #15834: URL: https://github.com/apache/iceberg/pull/15834#discussion_r3136760839
########## format/spec.md: ########## @@ -242,10 +242,12 @@ 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: - -* `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. +Non-default CRS values are specified by any string that uniquely identifies a coordinate reference system associated with this type. +To maximize interoperability, suggested (but not limited to) formats for CRS are: +* `<projjson>` - A complete CRS definition embedded directly using the [PROJJSON](https://proj.org/en/stable/specifications/projjson.html) specification. Example for `OGC:CRS83`: `{"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json","type": "GeographicCRS","name": "NAD83 (CRS83)","datum": {"type": "GeodeticReferenceFrame"...` Review Comment: From parquet discussion, we realized that none of the implementations actually use that, and that its difficult to implement it in practice for parquet readers, hence we left it only for backward compatability purposes. However, i'd like it to be "discouraged". Although it is most likely true, that while it makes it hard for parquet writers to implement this, its probably not hard for iceberg writer. with this in mind - wdyt ? -- 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]
