From eec4cf8e6891147b91049fc283727f837438a35a Mon Sep 17 00:00:00 2001 From: Kyle Barron Date: Sat, 1 Jun 2024 03:43:50 -0400 Subject: [PATCH] Clarify null/missing crs key (#225) --- format-specs/geoparquet.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/format-specs/geoparquet.md b/format-specs/geoparquet.md index d476139..6485008 100644 --- a/format-specs/geoparquet.md +++ b/format-specs/geoparquet.md @@ -65,7 +65,7 @@ The Coordinate Reference System (CRS) is an optional parameter for each geometry The CRS MUST be provided in [PROJJSON](https://proj.org/specifications/projjson.html) format, which is a JSON encoding of [WKT2:2019 / ISO-19162:2019](https://docs.opengeospatial.org/is/18-010r7/18-010r7.html), which itself implements the model of [OGC Topic 2: Referencing by coordinates abstract specification / ISO-19111:2019](http://docs.opengeospatial.org/as/18-005r4/18-005r4.html). Apart from the difference of encodings, the semantics are intended to match WKT2:2019, and a CRS in one encoding can generally be represented in the other. -If CRS is not provided, all coordinates in the geometries MUST use longitude, latitude based on the WGS84 datum, and the default value is [OGC:CRS84](https://www.opengis.net/def/crs/OGC/1.3/CRS84) for CRS-aware implementations. +If the `crs` key does not exist, all coordinates in the geometries MUST use longitude, latitude based on the WGS84 datum, and the default value is [OGC:CRS84](https://www.opengis.net/def/crs/OGC/1.3/CRS84) for CRS-aware implementations. Note that a missing `crs` key has different meaning than a `crs` key set to `null` (see below). [OGC:CRS84](https://www.opengis.net/def/crs/OGC/1.3/CRS84) is equivalent to the well-known [EPSG:4326](https://epsg.org/crs_4326/WGS-84.html) but changes the axis from latitude-longitude to longitude-latitude.