wgtmac commented on code in PR #240: URL: https://github.com/apache/parquet-format/pull/240#discussion_r1941436184
########## Geospatial.md: ########## @@ -0,0 +1,144 @@ +<!-- + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. See the NOTICE file + - distributed with this work for additional information + - regarding copyright ownership. The ASF licenses this file + - to you under the Apache License, Version 2.0 (the + - "License"); you may not use this file except in compliance + - with the License. You may obtain a copy of the License at + - + - http://www.apache.org/licenses/LICENSE-2.0 + - + - Unless required by applicable law or agreed to in writing, + - software distributed under the License is distributed on an + - "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + - KIND, either express or implied. See the License for the + - specific language governing permissions and limitations + - under the License. + --> + +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 be 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/ + +## Coordinate Reference System + +Coordinate Reference System (CRS) is a mapping of how coordinates refer to +locations on Earth. + +The default CRS `OGC:CRS84` means that the objects must be stored in longitude, +latitude based on the WGS84 datum. + +Custom CRS can be specified by a string value. It is recommended to use the +identifier of the CRS like [Spatial reference identifier][srid] and [PROJJSON][projjson]. + +For geographic CRS, longitudes are bound by [-180, 180] and latitudes are bound +by [-90, 90]. + +[srid]: https://en.wikipedia.org/wiki/Spatial_reference_system#Identifier +[projjson]: https://proj.org/en/stable/specifications/projjson.html + +## Edge Interpolation Algorithm + +An algorithm for interpolating edges, and is one of the following values: + +* `spherical`: edges are interpolated as geodesics on a sphere. +* `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 + +Two geospatial logical type annotations are supported: +* `GEOMETRY`: Geometry features in the WKB format with linear/planar edges interpolation. See [Geometry](LogicalTypes.md#geometry) +* `GEOGRAPHY`: Geography features in the WKB format with an explicit (non-linear/non-planar) edges interpolation algorithm. See [Geography](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) that are described below in detail. + +## Bounding Box + +A geometry has at least two coordinate dimensions: X and Y for 2D coordinates Review Comment: A related question: should we rename the `GeometryStatistics` to `GeospatialStatistics` to avoid confusion? -- 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...@parquet.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@parquet.apache.org For additional commands, e-mail: issues-h...@parquet.apache.org
