Of course, to activate the feature, you need Google Maps itself, ideally in the latest version. In principle, the trick also works with other navigation apps. In addition, download and start the free Android app Velociraptor.
Now follow the instructions displayed in the app.
Enable app permission for display overlay. The app will take you to the appropriate settings page.,Grant the app permission to use location. Finally, in order for the overlay to open automatically when you start a navigation app, you need to turn on the accessibility service. Once you’ve followed the steps in the app, you can now see your current speed in Google Maps based on GPS data and the maximum speed allowed. You can customize the icons and hide them if you wish. The app obtains the data for the permitted maximum speeds via the OpenStreetMap map service. The services TomTom Maps and HERE Maps can also be subscribed to for around one euro per month.
However, you should note that navigation apps are power guzzlers – an additional app that constantly measures your speed via GPS drains the battery even more. You should therefore always have a power bank for your smartphone or a car adapter with you to charge your cell phone in the car.