jiayuasu commented on code in PR #10981: URL: https://github.com/apache/iceberg/pull/10981#discussion_r1960747123
########## format/spec.md: ########## @@ -228,6 +230,30 @@ Notes: For details on how to serialize a schema to JSON, see Appendix C. +[1001]: <https://portal.ogc.org/files/?artifact_id=25355> "OGC Simple feature access" + +##### CRS + +For `geometry` and `geography` types, the parameter C refers to the CRS (coordinate reference system), a mapping of how coordinates refer to locations on Earth. + +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. Review Comment: @stefankandic In Iceberg Geo spec (as well as Parquet Geo spec), we explicitly enforce the x/y axis order to be `lon/lat` order and discard the axis order specified in the CRS. This is a common practice in the industry including Apache Sedona, GeoPandas, GeoArrow, ... This is to make sure that the tools can always have some basic operations on the the x/y values without looking into the CRS. Parsing CRS is a challenging task. With that in mind, OGC:CRS84 fits better as a default value. -- 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: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
