fitmod

README

fitmod

A CLI tool for injecting distance data into FIT activity files which lack GPS data.

Currently there are two ways of generating distance information:

• by directly specifying the total distance in kilometers,
• or by specifying the average speed in kilometers per hour.

The tool calculates the distance covered per record and updates each records distance field accordingly.

For details about the FIT protocol, see the official Garmin FIT documentation.

Motivation

Many stationary bikes or treadmills measure distance and speed locally, but do not transmit this data to the device recording the activity. As a result, the uploaded FIT activity may contain no usable distance information in services such as Garmin Connect or Strava.

fitmod provides a simple way to add this missing distance data to existing FIT activity files.

Installation

Go

go install github.com/huberbastian/fitmod@latest

Usage

fitmod currently supports two modes. The selected mode depends on which command line flag is provided.

Distance Mode

Generate distance data based on a target total distance using the --distance flag.

You can optionally specify an output path using --output. If omitted, the output file will be written as <input>_modified.fit.

Example:

fitmod process <input.fit> --distance <total-distance> --output <output.fit>

To inject a total distance of 50km into Indoor-Ride.fit:

fitmod process Indoor-Ride.fit --distance 50

Speed Mode

Generate distance data based on an average speed using the --speed flag.

The total distance is calculated from:

• the average speed,
• and the total activity duration derived from the FIT record timestamps.

Example:

fitmod process Indoor-Ride.fit --speed 25

If in doubt, run:

fitmod help