Hi,

I found a programming problem that calculated the speed between two cars as below and I would like to know how the calculation is done.

it is about determining the speed of two cars. The coordinate reference system (y,x) is attached to the ego vehicle (as shown in the attached figure).

The speed of the lead car is estimated with the radar of the ego vehicle.

As mentioned in the program reference: The true ground speed of a radar-reported object from the relative speed and the ego vehicle speed is calculated as follows:

Code:

(Vxi,Vyi) : relative object speed
egoSpeed : ego vehicle speed
[Vx,Vy] : ground object speed
Vx = Vxi + egoSpeed :Calculate longitudinal ground speed
theta = atan2(Vyi,Vxi) :Calculate heading angle
Vy = Vx * tan(theta) :Calculate lateral ground speed

Is there anyone who can explain how Vx and Vy are calculated? and why he uses the term "ground"?

Thank you.