sweref99-nu

PWA for showing current position in SWEREF 99 TM. Works offline after first visit.

Features

• Shows GNSS-derived coordinates in SWEREF 99 TM format
• Supports long-running averaging sessions for stationary measurements
• Keeps the device screen awake during averaging when the browser supports Wake Lock
• Works offline with ServiceWorker caching
• Compensates for ITRF/ETRS89 continental drift

Documentation

• LLMs file - Curated overview and documentation links for LLM and agent use
• SWEREF 99 Definition Verification - Complete verification of coordinate system definition with traceable references
• Software Bill of Materials - Direct runtime, build, and test dependencies with license references
• Test Suite Documentation - Overview of the current Jest-based unit test coverage

Development and testing

• Install dependencies with npm ci
• Run the test suite with npm test
• Build the browser bundle with make script.js
• The browser bundle is compiled from src/script.ts into _site/script.js for local testing and deployment
• For a working local site, serve _site/ on localhost after adding proj4.js and pico.min.css using the pinned downloads in .github/workflows/ci.yml; make script.js only compiles TypeScript. Geolocation and offline caching require localhost or HTTPS.
• The averaging button in the published UI starts a running mean over incoming SWEREF 99 samples, displays northing/easting with two decimals while active, and requests a screen wake lock when supported
• The project intentionally keeps the build/test stack minimal (TypeScript + Babel + Jest) and pins the small set of transitive overrides needed to keep the test runner secure and compatible with the supported Node runtime.

References

• https://developer.mozilla.org/en-US/docs/Web/API/Geolocation_API
• https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API
• https://picocss.com/docs
• https://github.com/proj4js/proj4js
• https://epsg.io/3006 - SWEREF 99 TM official specification