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Mar 28, 2022
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Expand WKB encoding to ISO WKB to support 3D geometries #45

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4 changes: 0 additions & 4 deletions README.md
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Expand Up @@ -18,10 +18,6 @@ Anyone is welcome to join us, by building implementations, trying it out, giving
Initial work started in the [geo-arrow-spec](https://github.com/geopandas/geo-arrow-spec/) GeoPandas repository, and that will continue on
Arrow work in a compatible way, with this specification focused solely on Parquet.

Note that version 0.1 only supports 2d geometries, as we are not supporting [EWKB](https://libgeos.org/specifications/wkb/#extended-wkb) or
[ISO WKB](https://libgeos.org/specifications/wkb/#iso-wkb). We expect to expand WKB to support 3D in the future, if you have thoughts please
sound in on #18 and/or follow along there.

## Goals

There are a few core goals driving the initial development.
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7 changes: 4 additions & 3 deletions format-specs/geoparquet.md
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Expand Up @@ -12,6 +12,7 @@ This is version 0.1.0 of the geoparquet specification.
## Geometry columns

Geometry columns are stored using the `BYTE_ARRAY` parquet type. They are encoded as [WKB](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary).
See the [encoding](#encoding) section below for more details.

## Metadata

Expand Down Expand Up @@ -94,9 +95,9 @@ Users are recommended to store their data in EPSG:4326 for it to work with the w

This is the binary format that the geometry is encoded in.
The string 'WKB', signifying [Well Known Binary](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary) is the only current option, but future versions
of the spec may support alternative encodings. This should be the ["standard"](https://libgeos.org/specifications/wkb/#standard-wkb) WKB
representation. This means 3D coordinates are not supported in this version of GeoParquet, but we expect
this to come in a future version.
of the spec may support alternative encodings. This should be the ["ISO"](https://libgeos.org/specifications/wkb/#iso-wkb) WKB representation. For two-dimensional geometries, this is identical to ["standard"](https://libgeos.org/specifications/wkb/#standard-wkb) WKB, but ISO WKB allows the use of 3D geometries.

Note that the current version of the spec only allows for a subset of ISO WKB: 2D or 3D geometries of the standard geometry types (the Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection geometry types). This means that M values or non-linear geometry types are not yet supported.

#### Coordinate axis order

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