jiayuasu commented on code in PR #10981:
URL: https://github.com/apache/iceberg/pull/10981#discussion_r1724114033
##########
format/spec.md:
##########
@@ -198,6 +199,9 @@ Notes:
- Timestamp values _with time zone_ represent a point in time: values are
stored as UTC and do not retain a source time zone (`2017-11-16 17:10:34 PST`
is stored/retrieved as `2017-11-17 01:10:34 UTC` and these values are
considered identical).
- Timestamp values _without time zone_ represent a date and time of day
regardless of zone: the time value is independent of zone adjustments
(`2017-11-16 17:10:34` is always retrieved as `2017-11-16 17:10:34`).
3. Character strings must be stored as UTF-8 encoded byte arrays.
+4. Coordinate Reference System, i.e. mapping of how coordinates refer to
precise locations on earth. Defaults to "OGC:CRS84". Fixed and cannot be
changed by schema evolution.
Review Comment:
1. When we say `OGC:CRS84`, the value you put in this field should be the
following PROJJSON string (see [GeoParquet
spec](https://github.com/opengeospatial/geoparquet/blob/main/format-specs/geoparquet.md#ogccrs84-details))
```
{
"$schema": "https://proj.org/schemas/v0.5/projjson.schema.json";,
"type": "GeographicCRS",
"name": "WGS 84 longitude-latitude",
"datum": {
"type": "GeodeticReferenceFrame",
"name": "World Geodetic System 1984",
"ellipsoid": {
"name": "WGS 84",
"semi_major_axis": 6378137,
"inverse_flattening": 298.257223563
}
},
"coordinate_system": {
"subtype": "ellipsoidal",
"axis": [
{
"name": "Geodetic longitude",
"abbreviation": "Lon",
"direction": "east",
"unit": "degree"
},
{
"name": "Geodetic latitude",
"abbreviation": "Lat",
"direction": "north",
"unit": "degree"
}
]
},
"id": {
"authority": "OGC",
"code": "CRS84"
}
}
```
2. Both `crs` and `crs_kind` field are optional. But when the `CRS` field
presents, the `crs_kind` field must present. In this case, since we hard code
this `crs` field in this phase, then we need to set `crs_kind` field (string)
to `PROJJSON`.
--
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
