So far, we have learned to obtain the user's location at a specific moment using the getCurrentPosition method. However, many applications require continuous tracking of the user's position, such as real-time navigation apps or those monitoring exercise routes. For this, the Geolocation API offers the watchPosition method, which allows receiving constant location updates. In this chapter, we will learn how to implement continuous tracking and explore some practical use cases.

What is the watchPosition Method?

The watchPosition method allows the application to receive periodic user location updates. Unlike getCurrentPosition, which obtains the location once, watchPosition runs each time there is a change in the user's location, providing updated real-time location data.

watchPosition Syntax

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Basic Implementation Example of watchPosition

In this example, we will see how to use watchPosition to update the user's latitude and longitude in real-time, displaying the information onscreen as the user moves.

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Stopping Real-Time Tracking with clearWatch

Although watchPosition is very useful for real-time tracking, it's important to stop it when no longer needed to save battery and device resources. To do this, we use the clearWatch method, which takes the watchId returned by watchPosition and stops the location updates.

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Complete Example with Start and Stop Buttons

A common approach in applications is to allow the user to turn location tracking on and off using start and stop buttons.

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Performance and Battery Usage Considerations

Continuous location tracking can consume a lot of battery, especially if the app requests high accuracy and the device uses GPS constantly. Therefore, it is important to limit the use of watchPosition to when it is strictly necessary. Here are some recommendations:

• Activate tracking only when needed by the user: Offer an option to turn tracking on/off instead of running it automatically.
• Reduce update frequency: Use the maximumAge option to reduce the number of updates requested.
• Deactivate when not needed: Ensure to stop tracking when leaving the view or activity where it was being used.

Advanced Configuration Example in watchPosition

For apps that need continuous tracking but seek to optimize resource usage, watchPosition can be configured with custom options that adjust accuracy and update frequency.

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Common Uses of watchPosition

Continuous location tracking is a key feature in apps that depend on real-time location:

• Navigation: Update the location on a map while the user moves.
• Exercise Apps: Monitor the progress of a route in activities like running or cycling.
• Transport Services: Track moving vehicles, like taxis or deliveries.

These applications rely on updated location data to provide a dynamic and accurate experience.

Chapter Summary

In this chapter, we explored how to implement continuous location tracking with the watchPosition method, a powerful tool for navigation and real-time tracking apps. We also covered how to optimize performance and stop tracking when not needed, maintaining a balance between precision and efficiency.

In the next chapter, we will see how to integrate geolocation data with map tools, allowing the user's location to be visually displayed on a map.

Let's move forward and discover how to integrate maps with the Geolocation API in the next chapter!