A parking lot usually has an in-gate and out-gate. When a vehicle comes in, a driver presses a button to a get parking ticket. Then, the gate opens. Some parking places use a card as driver identity. After it is tapped, the gate will open.

Here's a real parking gate:

To build a parking in-gate, we can design one as shown in the following figure. We put sensor devices on the left, right, and a front of a vehicle. You can use sensor devices that we have learned about.

For instance, we can use an ultrasonic sensor. We'll put some sensor devices on the right, left, and front of the vehicle. The sensor device position in the gate is shown in the following figure. All sensors acquire and obtain distance values, dx. Then, we set a threshold value from a collection of distance values to indicate whether a vehicle is present.

The out-gate has a similar design like the parking in-gate. You should modify the gate and sensor position based on the gate's position and size. Each gate will be identified as an in-gate or out-gate.

A gate will open if the driver has taken a parking ticket or taps a parking card. This scenario can be made automatic. For instance, we put a camera in front of the vehicle. This camera will detect the vehicle plate number. After detecting the plate number of the vehicle, the parking gate will open.

We will learn how to detect and identify plate numbers on vehicles using a camera in the next section.