Add geography type

apache · Dec 13, 2024 · 9f53c9e · 9f53c9e
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diff --git a/Geospatial.md b/Geospatial.md
@@ -0,0 +1,171 @@
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+
+Geospatial Definitions
+====
+
+This document contains the specification of geospatial types and statistics.
+
+# Background
+
+The Geometry and Geography class hierarchy and its Well-Known Text (WKT) and
+Well-Known Binary (WKB) serializations (ISO supporting XY, XYZ, XYM, XYZM) are
+defined by [OpenGIS Implementation Specification for Geographic information –
+Simple feature access – Part 1: Common architecture][sfa-part1], from [OGC
+(Open Geospatial Consortium)][ogc].
+
+The version of the OGC standard first used here is 1.2.1, but future versions
+may also used if the WKB representation remains wire-compatible.
+
+[sfa-part1]: https://portal.ogc.org/files/?artifact_id=25355
+[ogc]: https://www.ogc.org/standard/sfa/
+
+## Well-Known Binary
+
+Well-Known Binary (WKB) representations of geometries.
+
+Apache Parquet follows the same definitions of GeoParquet for [WKB][geoparquet-wkb]
+and [coordinate axis order][coordinate-axis-order]:
+- Geometries should be encoded as ISO WKB supporting XY, XYZ, XYM, XYZM. Supported
+standard geometry types: Point, LineString, Polygon, MultiPoint, MultiLineString,
+MultiPolygon, and GeometryCollection.
+- Coordinate axis order is always (x, y) where x is easting or longitude, and
+y is northing or latitude. This ordering explicitly overrides the axis order
+as specified in the CRS following the [GeoPackage specification][geopackage-spec].
+
+[geoparquet-wkb]: https://github.com/opengeospatial/geoparquet/blob/v1.1.0/format-specs/geoparquet.md?plain=1#L92
+[coordinate-axis-order]: https://github.com/opengeospatial/geoparquet/blob/v1.1.0/format-specs/geoparquet.md?plain=1#L155
+[geopackage-spec]: https://www.geopackage.org/spec130/#gpb_spec
+
+## Coordinate Reference System
+
+Coordinate Reference System (CRS) is a mapping of how coordinates refer to
+locations on Earth.
+
+Apache Parquet supports CRS Customization by providing following attributes:
+* `crs`: a CRS text representation. If unset, the CRS defaults to "OGC:CRS84".
+* `crs_encoding`: a standard encoding used to represent the CRS text. If unset,
+  `crs` can be arbitrary string.
+
+For maximum interoperability of a custom CRS, it is recommended to provide
+the CRS text with a standard encoding. Supported CRS encodings are:
+* `SRID`: [Spatial reference identifier][srid], CRS text is the identifier itself.
+* `PROJJSON`: [PROJJSON][projjson], CRS text is the projjson string.
+
+For example, if a Geometry or Geography column uses the CRS "OGC:CRS84", a writer
+may write a PROJJSON representation of [OGC:CRS84][ogc-crs84] to the `crs` field
+and set the `crs_encoding` field to `PROJJSON`.
+
+[srid]: https://en.wikipedia.org/wiki/Spatial_reference_system#Identifier
+[projjson]: https://proj.org/en/stable/specifications/projjson.html
+[ogc-crs84]: https://github.com/opengeospatial/geoparquet/blob/main/format-specs/geoparquet.md#ogccrs84-details
+
+## Edge Interpolation Algorithm
+
+The edge interpolation algorithm is used for interpreting edges of elements of
+a Geography column. It is applies to all non-point geometry objects and is
+independent of the [Coordinate Reference System](#coordinate-reference-system).
+
+Supported values are:
+* `spherical`: edges are interpolated as geodesics on a sphere. The radius of the underlying sphere is the mean radius of the spheroid defined by the CRS, defined as (2 * major_axis_length + minor_axis_length / 3).
+* `vincenty`: [https://en.wikipedia.org/wiki/Vincenty%27s_formulae](https://en.wikipedia.org/wiki/Vincenty%27s_formulae)
+* `thomas`: Thomas, Paul D. Spheroidal geodesics, reference systems, & local geometry. US Naval Oceanographic Office, 1970.
+* `andoyer`: Thomas, Paul D. Mathematical models for navigation systems. US Naval Oceanographic Office, 1965.
+* `karney`: [Karney, Charles FF. "Algorithms for geodesics." Journal of Geodesy 87 (2013): 43-55](https://link.springer.com/content/pdf/10.1007/s00190-012-0578-z.pdf), and [GeographicLib](https://geographiclib.sourceforge.io/)
+
+# Logical Types
+
+Apache Parquet supports the following geospatial logical type annotations:
+* `GEOMETRY`: Geometry features in the WKB format with linear/planar edges interpolation. See [Geometry logical type](LogicalTypes.md#geometry)
+* `GEOGRAPHY`: Geometry features in the WKB format with non-linear/non-planar edges interpolation. See [Geography logical type](LogicalTypes.md#geography)
+
+# Statistics
+
+`GeometryStatistics` is a struct specific for `GEOMETRY` and `GEOGRAPHY` logical
+types to store statistics of a column chunk. It is an optional field in the
+`ColumnMetaData` and contains [Bounding Box](#bounding-box) and [Geometry
+Types](#geometry-types).
+
+## Bounding Box
+
+A geometry has at least two coordinate dimensions: X and Y for 2D coordinates
+of each point. A geometry can optionally have Z and / or M values associated
+with each point in the geometry.
+
+The Z values introduce the third dimension coordinate. Usually they are used to
+indicate the height, or elevation.
+
+M values are an opportunity for a geometry to express a fourth dimension as a
+coordinate value. These values can be used as a linear reference value (e.g.,
+highway milepost value), a timestamp, or some other value as defined by the CRS.
+
+Bounding box is defined as the thrift struct below in the representation of
+min/max value pair of coordinates from each axis. Note that X and Y Values are
+always present. Z and M are omitted for 2D geometries. The concepts of westmost
+and eastmost values are explicitly introduced for Geography logical type to
+address cases involving antimeridian crossing, where xmin may be greater than
+xmax.
+
+```thrift
+struct BoundingBox {
+  /** Min X value for Geometry logical type, westmost value for Geography logical type */
+  1: required double xmin;
+  /** Max X value for Geometry logical type, eastmost value for Geography logical type */
+  2: required double xmax;
+  /** Min Y value for Geometry logical type, southmost value for Geography logical type */
+  3: required double ymin;
+  /** Max Y value for Geometry logical type, northmost value for Geography logical type */
+  4: required double ymax;
+  /** Min Z value if the axis exists */
+  5: optional double zmin;
+  /** Max Z value if the axis exists */
+  6: optional double zmax;
+  /** Min M value if the axis exists */
+  7: optional double mmin;
+  /** Max M value if the axis exists */
+  8: optional double mmax;
+}
+```
+
+## Geometry Types
+
+A list of geometry types from all geometries in the `GEOMETRY` or `GEOGRAPHY`
+column, or an empty list if they are not known.
+
+This is borrowed from [geometry_types of GeoParquet][geometry-types] except that
+values in the list are [WKB (ISO-variant) integer codes][wkb-integer-code].
+Table below shows the most common geometry types and their codes:
+
+| Type               | XY   | XYZ  | XYM  | XYZM |
+| :----------------- | :--- | :--- | :--- | :--: |
+| Point              | 0001 | 1001 | 2001 | 3001 |
+| LineString         | 0002 | 1002 | 2002 | 3002 |
+| Polygon            | 0003 | 1003 | 2003 | 3003 |
+| MultiPoint         | 0004 | 1004 | 2004 | 3004 |
+| MultiLineString    | 0005 | 1005 | 2005 | 3005 |
+| MultiPolygon       | 0006 | 1006 | 2006 | 3006 |
+| GeometryCollection | 0007 | 1007 | 2007 | 3007 |
+
+In addition, the following rules are applied:
+- A list of multiple values indicates that multiple geometry types are present (e.g. `[0003, 0006]`).
+- An empty array explicitly signals that the geometry types are not known.
+- The geometry types in the list must be unique (e.g. `[0001, 0001]` is not valid).
+
+[geometry-types]: https://github.com/opengeospatial/geoparquet/blob/v1.1.0/format-specs/geoparquet.md?plain=1#L159
+[wkb-integer-code]: https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary
diff --git a/LogicalTypes.md b/LogicalTypes.md
@@ -599,6 +599,51 @@ optional group variant_shredded (VARIANT) {
 }
 ```
 
+### GEOMETRY
+
+`GEOMETRY` is used for geometry features in the Well-Known Binary (WKB) format
+with linear/planar edges interpolation. See [Geospatial.md](Geospatial.md) for
+more detail.
+
+The type has two type parameters:
+- `crs`: An optional string value for Coordinate Reference System (CRS), which
+  is a mapping of how coordinates refer to locations on Earth. If unset, the CRS
+  defaults to "OGC:CRS84", which means that the geometries must be stored in
+  longitude, latitude based on the WGS84 datum.
+- `crs_encoding`: An optional enum value to describes the encoding used by the
+  `crs` field. Supported values are: `SRID`, `PROJJSON`. If unset, `crs` can be
+  arbitrary string.
+
+The sort order used for `GEOMETRY` is undefined. When writing data, no min/max
+statistics should be saved for this type and if such non-compliant statistics
+are found during reading, they must be ignored. 
+
+[`GeometryStatistics`](Geospatial.md#statistics) is introduced to store statistics
+for `GEOMETRY` type.
+
+### GEOGRAPHY
+
+`GEOGRAPHY` is used for geography features in the WKB format with non-linear/non-planar
+edges interpolation.
+
+The type has three type parameters:
+- `crs`: An optional string value for CRS, similar to `GEOMETRY` type. It must
+  be a geographic CRS, where longitudes are bound by [-180, 180] and latitudes
+  are bound by [-90, 90].
+- `crs_encoding`: An optional enum value, similar to `GEOMETRY` type.
+- `algorithm`: A required enum value to describes the edge interpolation
+  algorithm. Supported values are: `SPHERICAL`, `VINCENTY`, `THOMAS`, `ANDOYER`,
+  `KARNEY`. In order to correctly interpret edges interpolation of the geometries,
+  writer implementations should always set it and reader implementations should
+  fail for unknown values.
+
+The sort order used for `GEOGRAPHY` is undefined. When writing data, no min/max
+statistics should be saved for this type and if such non-compliant statistics
+are found during reading, they must be ignored. 
+
+[`GeometryStatistics`](Geospatial.md#statistics) is introduced to store statistics
+for `GEOGRAPHY` type.
+
 ## Nested Types
 
 This section specifies how `LIST` and `MAP` can be used to encode nested types

diff --git a/src/main/thrift/parquet.thrift b/src/main/thrift/parquet.thrift
@@ -242,13 +242,13 @@ struct SizeStatistics {
  * coordinates from each axis.
  */
 struct BoundingBox {
-  /** Westmost value (min longitude) on the X axis */
+  /** Min X value for Geometry logical type, westmost value for Geography logical type */
   1: required double xmin;
-  /** Eastmost value (max longitude) on the X axis */
+  /** Max X value for Geometry logical type, eastmost value for Geography logical type */
   2: required double xmax;
-  /** Southmost value (min latitude) on the Y axis */
+  /** Min Y value for Geometry logical type, southmost value for Geography logical type */
   3: required double ymin;
-  /** Northmost value (max latitude) on the Y axis */
+  /** Max Y value for Geometry logical type, northmost value for Geography logical type */
   4: required double ymax;
   /** Min Z value if the axis exists */
   5: optional double zmin;
@@ -260,7 +260,7 @@ struct BoundingBox {
   8: optional double mmax;
 }
 
-/** Statistics specific to GEOMETRY logical type */
+/** Statistics specific to Geometry and Geography logical types */
 struct GeometryStatistics {
   /** A bounding box of geometries */
   1: optional BoundingBox bbox;
@@ -417,33 +417,62 @@ struct BsonType {
 struct VariantType {
 }
 
-/** Physical type and encoding for the geometry type */
-enum GeometryEncoding {
-  /**
-   * Allowed for physical type: BYTE_ARRAY.
-   *
-   * Well-known binary (WKB) representations of geometries.
-   */
-  WKB = 0;
+/** Coordinate reference system (CRS) encoding for Geometry and Geography logical types */
+enum CRSEncoding {
+  SRID = 0;
+  PROJJSON = 1;
+}
+
+/** Edge interpolation algorithm for Geography logical type */
+enum EdgeInterpolationAlgorithm {
+  SPHERICAL = 0;
+  VINCENTY = 1;
+  THOMAS = 2;
+  ANDOYER = 3;
+  KARNEY = 4;
 }
 
 /**
- * GEOMETRY logical type annotation (added in 2.11.0)
+ * Embedded Geometry logical type annotation
+ *
+ * Geometry features in the Well-Known Binary (WKB) format with linear/planar
+ * edges interpolation.
  *
- * GeometryEncoding is required. In order to correctly interpret geometry data,
- * writer implementations SHOULD always set it, and reader implementations
- * SHOULD fail for unknown values.
+ * A custom CRS can be set to the crs field. If unset, the CRS defaults to
+ * "OGC:CRS84", which means that the geometries must be stored in longitude,
+ * latitude based on the WGS84 datum.
  *
- * CRS is optional. A custom CRS and its corresponding encoding can be set to
- * crs and crs_encoding fields respectively. If missing, the CRS defaults to
- * "OGC:CRS84".
+ * crs_encoding is an auxillary field to help decode the crs text. If unset, the
+ * crs field can be arbitrary text.
  *
- * See LogicalTypes.md for detail.
+ * Allowed for physical type: BYTE_ARRAY.
  */
 struct GeometryType {
-  1: required GeometryEncoding encoding;
-  2: optional string crs;
-  3: optional string crs_encoding;
+  1: optional string crs;
+  2: optional CRSEncoding crs_encoding;
+}
+
+/**
+ * Embedded Geography logical type annotation
+ *
+ * Geometry features in the WKB format with non-linear/non-planar edges
+ * interpolation.
+ *
+ * Similar to the Geometry logical type, a custom CRS can be set to the crs and
+ * crs_encoding fields. However, Geography logical type must use a geographic
+ * CRS, where longitudes are bound by [-180, 180] and latitudes are bound by
+ * [-90, 90].
+ *
+ * algorithm is required. In order to correctly interpret edges interpolation
+ * of the geometries, writer implementations should always set it and reader
+ * implementations should fail for unknown values.
+ *
+ * Allowed for physical type: BYTE_ARRAY.
+ */
+struct GeographyType {
+  1: optional string crs;
+  2: optional CRSEncoding crs_encoding;
+  3: required EdgeInterpolationAlgorithm algorithm;
 }
 
 /**
@@ -919,8 +948,8 @@ struct ColumnMetaData {
    */
   16: optional SizeStatistics size_statistics;
 
-  /** Optional statistics specific to GEOMETRY logical type */
-  17: optional GeometryStatistics geometry_stats;
+  /** Optional statistics specific for Geometry and Geography logical types */
+  17: optional GeometryStatistics geometry_statistics;
 }
 
 struct EncryptionWithFooterKey {
@@ -1053,6 +1082,7 @@ union ColumnOrder {
    *   MAP - undefined
    *   VARIANT - undefined
    *   GEOMETRY - undefined
+   *   GEOGRAPHY - undefined
    *
    * In the absence of logical types, the sort order is determined by the physical type:
    *   BOOLEAN - false, true