s3bad / geoarrow

Specifications for storing geospatial data in Apache Arrow and Apache Parquet

GeoArrow - geospatial data with Apache Arrow

Specifications for storing geospatial data in Apache Arrow.

The Apache Arrow project specifies a standardized language-independent columnar memory format. It enables shared computational libraries, zero-copy shared memory and streaming messaging, interprocess communication, etc and is supported by many programming languages and data libraries.

Spatial information can be represented as a collection of discrete objects using points, lines and polygons (i.e., vector data). The Simple Feature Access standard provides a widely used abstraction, defining a set of geometries: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, GeometryCollection. Next to a geometry, simple features can also have non-spatial attributes that describe the feature.

Geospatial data often comes in tabular format, with one or more columns with feature geometries and additional columns with feature attributes. The Arrow columnar memory model is therefore perfectly suited to store such data, both vector features and their attribute data. The GeoArrow specification defines how the vector features (geometries) can be stored in Arrow (and Arrow-compatible) data structures.

This repository contains the specifications for:

• The memory layout for storing geometries in an Arrow field (format.md)
• The Arrow extension type definitions (extension-types.md)

Defining a standard and efficient way to store geospatial data in the Arrow memory layout helps interoperability between different tools and ensures geospatial tools can leverage the growing Apache Arrow ecosystem:

• Efficient, columnar file formats. Leveraging the performant and compact storage of Apache Parquet as a vector data format in geospatial tools using GeoParquet.
• Accelerated between-process geospatial data exchange using Apache Arrow IPC message format and Apache Arrow Flight
• Zero-copy in-process geospatial data transport using the Apache Arrow C Data Interface (e.g., GDAL)
• Shared libraries for geospatial data type representation and computation for query engines that support columnar data formats (e.g., Velox, DuckDB, Acero)

The goal of this repository is to discuss and move towards specifications on metadata and memory layout for storing geospatial data in the Arrow memory layout or related formats.

Relationship with GeoParquet

The GeoParquet specification originally started in this repo, but was moved out into its own repo (https://github.com/opengeospatial/geoparquet), leaving this repo to focus on the Arrow-specific specifications (Arrow layout and extension type metadata).

Implementations

• geoarrow-c: geospatial type system and generic coordinate-shuffling library written in C with bindings in C++, R, and Python
• geoarrow-rs: Rust implementation of the GeoArrow specification and bindings to GeoRust algorithms for efficient spatial operations on GeoArrow memory. Includes JavaScript (WebAssembly) bindings.