What Is an Activity Tracker and How Does a GPS Activity Tracking App Work?

Updated

An activity tracker is software or hardware that records movement data for activities such as hiking, running, or cycling. A GPS-based tracker app does this by logging your position over time and saving the result as a track file. AAT Another Activity Tracker is a concrete example: an open-source Android app that records activities, stores tracks in standard GPX format, and doubles as a map viewer with offline map support. This explanation covers what these apps do, how the recording and storage work, and what to check before choosing one.

What an activity tracker actually does

The core job is simple: capture where you went and when, then keep that record in a usable form. For a GPS tracker app, that means:

  • Sampling your position at intervals while you move.
  • Turning those points into a continuous track (a route line).
  • Saving the track so you can review, share, or reuse it later.

Some trackers add sensors (heart rate, steps, cadence), but GPS route recording is the baseline function. AAT focuses on that baseline plus map viewing, rather than on fitness metrics.

How GPS tracking and GPX storage work

A GPS receiver in your phone reports latitude, longitude, and usually altitude. The app records these as a sequence of points with timestamps.

The key design choice is the file format. AAT stores tracks in standard GPX format. GPX (GPS Exchange Format) is a widely supported, text-based format for routes, tracks, and waypoints. Practically, this matters because:

  • A GPX file can be opened by many other mapping and fitness tools, not just the app that created it.
  • You are not locked into one vendor's ecosystem to read your own data.
  • Tracks can be edited or planned and then loaded back in.

AAT also includes a simple GPX editor for quick route planning, so you can sketch a route rather than only record one.

Common features in a GPS tracker app

Using AAT's feature set as the reference, a GPS activity tracker typically offers:

Feature What it gives you
Cockpit and map views Switch between a data readout and a map while recording
Offline and tile-based maps Maps available without a live connection, plus online tiles
Global map coverage Maps for areas beyond your home region
GPS-independent altitude and hill shading Terrain context that does not rely solely on the GPS altitude reading
Offline POI support Points of interest available without a network
GPX editor Plan or adjust routes before or after a trip

The offline map capability is the feature most likely to decide whether an app suits you. If you hike or ride outside network coverage, offline maps and offline POIs are the difference between a usable and an unusable tool.

General tracker vs. a dedicated open-source GPS app

These are not the same category:

  • General activity trackers often bundle step counting, sleep, heart rate, and social features, and may push data to a vendor account.
  • A dedicated GPS tracker app like AAT concentrates on recording tracks, viewing maps, and keeping data in an open format. AAT is open-source and licensed under GPL, which means the source is available to inspect, modify, and redistribute under that license.

If your priority is fitness metrics and a polished consumer dashboard, a general tracker fits better. If your priority is owning your route data in GPX and working with offline maps, a dedicated open-source tracker fits better.

Practical considerations before you install one

  • Map coverage and offline use. Confirm the app supports offline maps for the regions you actually travel in.
  • GPX compatibility. Check that tracks export as GPX so you can move them between tools.
  • Altitude accuracy. GPS altitude is often less reliable than horizontal position; features like GPS-independent altitude and hill shading help compensate.
  • Distribution and trust. AAT is available as source on GitHub and as a binary on F-Droid. F-Droid is an app repository that distributes free and open-source Android software, which is a relevant signal if you prefer not to use closed app stores.
  • Platform. AAT runs on Android, so it is not an option on other mobile platforms.

Where to get it

AAT Another Activity Tracker is distributed two ways: source code from GitHub, and a binary build from F-Droid. If you want to verify or modify the app, use the source; if you just want to install it on an Android device, the F-Droid binary is the straightforward path.