The app records the audio of your serve and films the ball flying into the service box. Algorithms then try to recognize the time your racket hits the ball and the time at which the ball landed on the court. From the video data, the app computes where the ball has landed. The flight time and distance travelled by the ball, as well as the effect of air drag and the speed of sound, are taken into account to compute the average and maximum speed of your serve. The maximum speed is the speed that is usually shown on the display at big Tennis tournaments.

To track serves with this app, you need a mobile device with a camera and microphone, running either Android or iOS. The more powerful the CPU and the more RAM, the better.

Also, you need a tripod to mount your device. Your device should be completely static (i.e., not move at all) and in a height of approximately 160cm - 190cm (5ft - 7ft).

Simply follow the instructions provided by the app. You can always click the speaker symbol to have a voice assistant explain the next steps to you. Also, you can check out the short explanation videos and 'Help' buttons where available. For your convenience, in the FAQ section inside the app, you can find all video tutorials to check out how the app is operated.

Your mobile device does not have a radar sensor (unfortunately). For this reason, the app needs to approximate the flight path and flight time of the ball by using the audio and video data provided by your device. We have calibrated and tuned our algorithms against a commercial radar gun. We found the results computed by our app to satisfy the requirements of hobby tennis players and trainers in the leisure sports sector. However, just like in every other indirect measurement approach, there is some variance involved in the results produced by the app. To see how the app compares to the measurements of a radar gun, check out our videos on YouTube.

With the Free Version you can test whether the app can track your serves well in your environment (i.e., on your courts). You can track serves in the 'Manual Mode' to check if the serve and bounce were correctly recognized in both the audio and video.

If you are satisfied with the tracking, you can buy the Premium Version to see the speed of your serves, additional details and statistics, and to use the 'Automatic Mode'. If the Free Version does not work correctly on your device, I do not recommend buying the Premium Version as it uses the same algorithms.

No, your serves and statistics will not be stored (neither on your device nor online). They are only available at runtime of the app and will be deleted from the working memory when you close the app.

No, all video and audio data captured by the app will be processed only locally and will never leave your device.

Since the app uses both audio and video data, several conditions must be ensured:

Audio: The environment should be as quiet as possible (optimally: no noise from other courts, no echo, no wind, no talking, no other environmental noise, etc.).

Video: The camera must not move during the recording. Nothing should move in the video except for the ball (i.e., no people in the background, no movement of the net or trees in the background, no moving shadows on the court, no wind shaking the camera, etc.). Water clay courts sufficiently to prevent dust and to ensure a good visual contrast between the court surface and the ball.

We strongly recommend tracking serves outdoors because indoor courts tend to produce strong echoes sometimes disturbing the measurement (especially the recognition of the bounce in the audio signal). When tracking outdoors, echoes are usually not a problem.

The app could not detect the ball flying into the service box.

Try:

(1) re-position your camera closer to the service box.

(2) increase the 'Detection Sensitivity' in the 'Audio & Video' settings.

(3) increase the 'Resolution' in the 'Audio & Video' settings.

(4) use a darker court that better contrasts the color of the ball.

The app detects movement in the image and falsely interprets it as the ball flying into the service box or net.

Try:

(1) ensure that no movement in the background or on the court is visible during the recording (e.g., no people, no moving trees or shadows). Avoid using the app when there is wind.

(2) switch off 'Detect Net Serve' in the 'Player & Serve' settings.

(3) decrease the 'Detection Sensitivity' in the 'Audio & Video' settings.

The app could not correctly find the serve and/or bounce in the audio signal. This is usually due to noise (e.g., sounds from other courts, echo, wind, people speaking, sounds from the environment).

Try:

Ensure an echo-free and quiet environment.

The app could not correctly reconstruct the flight path of the ball. This is usually because the app has captured too few good images of the ball flying in and out of the service box. Reasons can be numerous (e.g., serve too fast for capturing frame rate, frame rate low due to overheating of your device). In general, the app achieves the best performance on iOS devices (modern iPhones or iPads).

Try:

(1) cool down your device by placing it in the shadow.

(2) switch 'RAM Saving' to 'Off' in the 'Audio & Video' settings.

(3) reduce the 'Resolution' in the 'Audio & Video' settings.

(4) use a more powerful device.

To measure the speed of a specific type of serve, we strongly recommend recording at least 10 (or more) of these serves, for example in the 'Automatic Mode'. The average speed (and %-in scores) displayed in the statistics screen after the batch are most suitable to learn about the specific type of serve measured. Don't just rely on 2 or 3 individual serve recordings. The more serves (of the specific type that interests you) you'll measure, the more precise the average scores will reflect your true performance.

To use the app in a private mode and avoid others hearing the app's audio feedback, you can simply connect your bluetooth headphones to your device. When doing so, restart the app and make sure that your device's microphone (not the bluetooth microphone!) is selected in the 'Audio & Video' settings. This is important to ensure that the app can still hear the bounce well.

To ensure the audio signal and the results can be heard well by the server and/or spectators, you can simply connect a bluetooth speaker to your device. When doing so, restart the app and make sure that your device's microphone (not a bluetooth microphone!) is still selected in the 'Audio & Video' settings. This is important to ensure that the app can still hear the bounce well using the microphone on your phone or tablet.

To get access to new features, regularly check if app updates are available in the Google Play Store or the Apple App Store. For this, just click on 'Info & Updates' in the lower right corner when using the app, and then on 'Check for Updates'.

If you have any feedback (positive or negative), or if you have a great idea for a cool new feature that you would love to see being integrated in a future update, please do not hesitate to get in touch! 😀

We love improving the app based on your constructive feedback and ideas!

Just reach out to André via e-mail!