How does the CoronaMelder app measure the distance to other users of the app?
Mobile phones with the CoronaMelder app installed exchange data via Bluetooth codes when they are near to each other. The app estimates whether you are within 1.5 metres of anyone else. The CoronaMelder app uses a special type of Bluetooth for this, called Bluetooth Low Energy. This enables the app to detect whether you have been near someone who is also using the app. The stronger the Bluetooth signal, the closer you were.
The measurements performed by the CoronaMelder app add up. If you have been close to more than one infected person on more than one occasion on the same day and those contacts add up to 15 minutes within a distance of 1.5 metres, you will also get a notification. This is because multiple short-lasting, high-risk contacts increase the risk of infection.
Scientific research has shown that the CoronaMelder app notifications are reliable. In most cases, the distance measured by the app is accurate. To be precise:
- In 84% of the cases that someone should be notified, this also happens.
- In 74% of the cases that someone should not be notified, this does not happen.
If there is a wall between two mobile phones that have the CoronaMelder app installed, the signal is weakened. If you are within 1.5 metres of someone and there is a wall between you, you are unlikely to get a notification.
The app does not have any data on your location, name, email address, phone number or other contact details. The app does not know who you or the other person are, or where you are.