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StevenMaude / armstrong

:satellite::watch: Update expired Extended Prediction Orbit (EPO) GPS data for Garmin devices, e.g. Forerunner watches. Spend less time waiting for a GPS fix before a run or cycle *without* Garmin's software!
GNU General Public License v2.0
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epo garmin go golang gps watch

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armstrong

About

Retrieve EPO.BIN GPS data from Garmin's servers on any platform that you can compile a Go binary for, rather than only those that support Garmin Connect. Since Garmin's software doesn't run natively on Linux, it's useful there.

EPO.BIN is GPS Extended Prediction Orbit (EPO) satellite data valid for 7 days, used to help speed up GPS locking on Garmin devices that support this.

For Forerunner devices, the file should be copied to GARMIN/REMOTESW/EPO.BIN on the watch.

Alternatives

There are other existing options, e.g. running curl and then a short Ruby script as detailed in this blog post, or using postrunner, a more complete application which also uses Ruby. However, this code can be compiled into a standalone binary, for different platforms, and then run without any dependencies.

Don't want to run at all?

This repository hosts a daily download of EPO.BIN.

Usage

Download

If you don't want to build from source, Linux and Windows binaries are built from tagged versions via GitHub Actions.

Build

With Go installed:

Or, use the Dockerfile via make:

Run

Just run the compiled binary. EPO.BIN should be generated in the same directory.

Credits

Code uses the POST data and idea from the blog post here and is also based on the GPL v2 licensed code in postrunner, specifically EPO_Downloader.rb. Go code is my contribution.