geoarrow-js

A minimal TypeScript implementation of GeoArrow building on top of Arrow JS.

It complements the work-in-progress geoarrow-wasm, which will provide Rust-based operations on GeoArrow memory.

Features

• Performant spatial operations.
• Rich static typing of geometry arrays.
• Tree shakeable.
• Utilities for sharing Arrow data across Web Workers (not specific to GeoArrow)

Spatial operations

Only spatial operations that are implemented on binary representations of geometry will be added to this repo.

This means that geoarrow-js will not, say, use algorithms from Turf, because that would require conversions to and from GeoJSON for the operation.

Implemented algorithms:

Refer to the algorithm namespace in the docs.

• Polygon area and signed area (via @math.gl/polygon)
• Polygon winding order (via @math.gl/polygon)
• Polygon triangulation (via @math.gl/polygon, a fork of earcut.)
• Coordinate reprojection (via proj4)
• Total bounds (the bounding box of an array of geometries).

Web Worker utilities

Refer to the worker namespace. Note that due to limitations in Arrow JS (as of v14) you must use preparePostMessage before a call to structuredClone or postMessage, to ensure it can correctly be rehydrated on the worker.

import * as arrow from "apache-arrow";
import {
  preparePostMessage,
  rehydrateVector,
} from "@geoarrow/geoarrow-js/worker";

const originalVector = arrow.makeVector(new Int32Array([1, 2, 3]));
const [preparedVector, arrayBuffers] = preparePostMessage(originalVector);

// Here we use structuredClone to simulate a postMessage but on the main thread
const receivedVector = structuredClone(preparedVector, {
  transfer: arrayBuffers,
});
const rehydratedVector = rehydrateVector(receivedVector);
Copy

Ecosystem

geoarrow-js is designed to be used seamlessly with WebAssembly-based GeoArrow operations, such as those in the JavaScript bindings of the Rust GeoArrow implementation, and with rendering libraries, such as deck.gl, with the help of @geoarrow/deck.gl-layers.

For more background on my plans for GeoArrow ecosystem in JS and WebAssembly, refer to this thread.