How to interpret an Ambiguity function
The ambiguity function is used in radar systems to get the distance and the relative speed of a moving object with respect to the transmitter. Is called ambiguity because it also tells about the ability to distinguish objects that are close between them and with a similar vector velocity. 

The ideal ambiguity function is a Delta function in both domains. However there is no waveform with this ambiguity function. With your Barker-Code, you could have troubles to identify different objects that are at a distance +/- &lt;10us, and whose Doppler is +/- &lt;10 kHz. But you could distinguish two objects that are at 5us, one with 5 KHz and the other with 27 kHz.

In order to estimate the Doppler and the delay, you first compute the ambiguity function between the Barker-Code and the reflected signal. You will get a noisy version of the above figure but shifted in both domains, depending on the delay and Doppler of the target. If there are more targets, you will obtain overlapped ambiguity functions, each one shifted in a different place on the correlation plane. 

You then just find the position of the maximum. From the obtained Doppler you can get the speed with the equation you wrote.