@developmentseed/epsg

The full EPSG projection database, compressed to 309kb for the web.

Some existing EPSG amalgamations exist, but all are uncompressed, incomplete, outdated, and/or not reproducible [^1] [^2] [^3] [^4]. This package uses the DecompressionStream API, now widely available in browsers, to bundle a gzip-compressed text file of WKT definitions for all 7352 defined EPSG projection codes.

[^1]: epsg includes only 3912 definitions, stores older, deprecated proj strings, and is uncompressed, coming to 500kb.

[^2]: epsg-index stores extra parsed information for each projection and is 7.7 MB.

[^3]: proj4-list includes only 5434 definitions, stores older, deprecated proj strings, and is 759KB of uncompressed strings.

[^4]: @esri/proj-codes ships a lot of redundant information, coming to nearly 15MB of JSON.

Usage

Currently, the only package entrypoint is @developmentseed/epsg/all, which loads a Map<number, string>, with all EPSG definitions in OGC WKT2 format.

import loadEPSG from "@developmentseed/epsg/all";
import proj4 from "proj4";

// Load the EPSG database
const epsg = await loadEPSG();

// Access WKT strings by EPSG code.
const wkt4326 = epsg.get(4326);
const wkt3857 = epsg.get(3857);

// Then use proj4.js as normal
const converter = proj4(wkt4326, wkt3857);
const inputPoint = [1, 52];
const outputPoint = converter.forward(inputPoint);

Generate new EPSG definitions

First, download the latest EPSG definitions in WKT format. Go to epsg.org/download-dataset.html, create an account or log in, then download the WKT File version.

Then, from this directory, run

python scripts/generate.py

Then the file src/all.csv.gz will be updated with the latest EPSG definitions.

Publishing

The build script in package.json will automatically include all.csv.gz in the published NPM package.

If you get an error like

cp: dist/all.csv.gz: No such file or directory

You may need to delete an errant tsconfig.build.tsbuildinfo and try again. I'm not sure why.