The free app, GPS Speedometer - Odometer App, is designed for measuring the speed of vehicles.  It supports different units, including kph (kilometer per hour), mph (miles per hour), and knots.

Portrait and landscape are the two (heads-up display) HUD speedometer mode that helps you while traveling and driving a car. The app displays the tracking map and your speed.

In this app, you can also set your speed limit, and notifies you when you go beyond the speed limit.

It has a simple and intuitive interface. To start measuring, select the unit.