How to Correct GPS Drift on the Coros Apex Pro

Introduction

The Coros Apex Pro is a high‑end multisport GPS watch that many runners, cyclists, and trail athletes trust for accurate pacing, elevation, and route data. Like all consumer GPS devices, it is not immune to drift—an incremental error that can accumulate over long rides or races. While the built‑in satellite network usually keeps the watch within a few meters of true position, occasional misalignments can happen due to signal interference, atmospheric conditions, or internal sensor quirks.

This guide walks you through the most common techniques for correcting GPS drift on the Apex Pro. We’ll cover why drift occurs, how to spot it, and a step‑by‑step process for real‑time adjustment and long‑term calibration. By the end you’ll be able to keep your Apex Pro’s map data precise, ensuring that split times, total distance, and elevation gains stay reliable.

Understanding GPS Drift

GPS drift is a subtle, continuous error that can arise when the watch’s satellite calculations deviate slightly from reality. Unlike sudden jumps, drift accumulates gradually, making the watch believe it has moved farther or closer than it really has. Because the Apex Pro constantly uses data from the GPS, GLONASS, Galileo, and BeiDou constellations, a small error in any one of these can affect the final position.

Typical symptoms include:

• Distance mismatches: the watch reports 5 km while a GPS receiver or map shows 4.95 km.
• Split inconsistencies: a 5‑km split appears 100 m longer than expected.
• Elevation glitches: a hill that should be 60 m high is logged as 70 m.
• Map wandering: the on‑screen path jumps a few meters from the real route.

Recognizing these tells you that drift is present and that a correction is needed.

Common Causes of Drift on the Apex Pro

1. Satellite signal loss or multipath – In dense urban areas, buildings reflect signals, creating false positions.
2. Atmospheric disturbances – Ionospheric and tropospheric delays can skew distance calculations.
3. Thermal expansion – Extreme heat or cold can slightly alter sensor performance.
4. Firmware or sensor firmware lag – Out‑of‑date software may not handle new correction data optimally.
5. User errors – Not waiting for a full satellite fix before starting a ride or using “track only” mode can introduce errors.

Understanding the culprit helps you choose the right correction technique.

Preparation Before Correcting

1. Ensure Latest Firmware

Navigate to Settings → System → Firmware Update. If an update is available, install it. New firmware often includes improved algorithms for satellite correction.

2. Clear Existing Data

Before adjusting anything, clear past GPS logs to avoid blending old drift with new corrections.

• Go to Activities → History.
• Select a ride, tap Delete.
• Repeat for any relevant sessions.

3. Secure a Good Satellite Fix

Before you start, wear the watch for at least 5–10 minutes in an open area. A strong fix requires 6–8 satellites with good geometry. On the watch screen, you’ll see a satellite count icon. Aim for 8+ satellites.

Real‑Time Calibration Steps

1. Enable “High Accuracy” Mode

While running, cycling, or hiking, activate Settings → GPS → Mode → High Accuracy. This forces the watch to use all available constellations and to prioritize signal quality over battery life.

2. Use the “Calibrate” Feature

The Apex Pro offers an in‑watch calibration function that leverages known reference points.

• During a ride: When you reach a known spot (e.g., a mile marker or a park bench you’ve measured), pause the activity.
• Press Menu → Settings → Calibration → GPS Calibration.
• Enter the exact latitude, longitude, and elevation you’ve measured beforehand.
• The watch will adjust its internal model to align with that reference.

Repeat at least twice during a session if you notice persistent drift.

3. Monitor the “Position Offset” Indicator

On the main screen, you’ll find a Position Offset icon (looks like two arrows). A value near zero means the watch’s internal position aligns well with real GPS data. If it reads a positive or negative number, the watch is off by that many meters.

Post‑Ride Correction Using the App

After you finish, you can refine the data in the Coros app on your smartphone or computer.

1. Sync the Activity – Connect the watch to the app via Bluetooth.
2. Open the Activity – Tap the session you just completed.
3. Access “Edit” – Look for an option that says Correct GPS or Trim GPS.
4. Select a Known Reference Point – If you had a GPS‑accurate device (e.g., a smartphone or a professional GPS receiver), you can overlay its data and tell the app where the apex was wrong.
5. Apply the Correction – The app will automatically shift the entire route to match the reference, preserving splits and elevation data.

The corrected activity will now display accurate splits, distance, and elevation.

Using External Reference Devices

If you have a handheld GPS or a smartphone with an accuracy of ±3 m, you can use it to correct the Apex Pro.

Step‑by‑Step

1. Record a Parallel Session – Wear the Apex Pro and your external device on the same route.
2. Export Both Tracks – Save the Apex Pro activity to the app and export the external track as a GPX file.
3. Import to a Desktop Tool – Use software like Garmin BaseCamp, Strava, or GoldenCheetah to overlay the two tracks.
4. Identify Deviations – Find the segments where the Apex Pro track deviates.
5. Create a “Correction” File – Some tools let you generate a correction GPX that contains the offset.
6. Import Back to the App – In the Coros app, choose Upload Correction (if supported) or manually adjust splits in the activity editor.

This method gives you the most precise adjustment, especially for long endurance events.

Advanced Options for Experienced Users

1. Adjusting the “Antenna Offset”

The Apex Pro allows a manual adjustment of the antenna position in its firmware. If you consistently see a small but steady drift in a particular direction, you can tweak this setting.

• Go to Settings → System → Advanced → Antenna Offset.
• Enter a small value (e.g., 0.5 m) and observe the effect in a test ride.

Use this only if you understand the impact on all subsequent rides.

2. Using the “External Compass” Feature

In certain terrains, a magnetic disturbance can affect GPS. Enabling an external compass can help.

• Go to Settings → Sensors → Compass.
• Turn on External Compass.
• Follow the on‑screen calibration prompts.

This feature can subtly improve position accuracy, especially in high‑altitude or magnetically noisy areas.

3. Customizing Satellite Weights

If you notice that GLONASS signals are weaker or Galileo is unreliable in your region, you can bias the watch to prefer GPS.

• Settings → GPS → Satellite Preference.
• Choose GPS Only or Prioritize GPS.

This reduces the risk of drift from weaker constellations.

Preventing Drift: Best Practices

• Start with a Strong Fix – Always wait until you have 8+ satellites before beginning a ride.
• Avoid “Track Only” Mode – This mode reduces battery life and can cause sudden loss of fix.
• Regularly Update Firmware – Coros releases updates that refine GPS algorithms.
• Use Known Landmarks – Whenever possible, pause at a known marker and calibrate.
• Keep the Watch Clean – Dirt or debris on the antenna can degrade signal quality.
• Store Properly – Extreme temperatures can affect the internal electronics; avoid prolonged exposure to heat or cold.

Following these habits will keep drift to a minimum and maintain your Apex Pro’s reliability.

Troubleshooting Common Issues

If none of the fixes help, contact Coros support with your activity logs.

Sample Workflow for a Marathon

1. Pre‑Race – In the 3‑day break before the marathon, test the watch in an open area. Verify 8+ satellites and perform a GPS calibration at a known spot.
2. Race Start – Once the finish line is over the line, allow the watch to lock for a few seconds before hitting “Start.”
3. Mid‑Race Checks – At the 10‑km, 20‑km, and 30‑km marks, pause briefly. Look at the Position Offset indicator. If it deviates beyond ±3 m, run the calibration procedure.
4. Post‑Race – Sync the activity, then use the app’s “Correct GPS” feature if you have an external reference.
5. Analysis – Review the splits and elevation. If all values align with expected metrics, you’ve successfully corrected drift.

Final Thoughts

GPS drift is a normal part of using any consumer GPS device. On the Coros Apex Pro, the combination of built‑in calibration tools, firmware updates, and external reference options gives athletes a robust toolkit for maintaining positional accuracy. By following the steps above, you can ensure that your recorded routes truly reflect your effort, leading to more reliable training data and better race analysis.

Remember: a well‑calibrated watch is the foundation of trustworthy metrics. Treat it with care, keep the firmware current, and use the calibration features whenever the need arises. Happy riding, running, and hiking!