# Methods for digital signal comparison?

Started by December 13, 2004
```Hello wizards,

Is there a "best" known way for comparing two finite-same-sized
digital signals? I want a good way to measure the degree of similarity
of the *shape* of the two signals. This is for comparing magnetic
signatures of vehicles.

Is the best way just to do a scaled cross correlation between the two
signals?

--Shafik

```
```Errr, find the correlation?

If I remember correctly, remove the DC, multiply and sum the terms of
series A and B..
ie sum = a1*b1 + a2+b2 +.....
The sum will be proportional to the correlation between the two
signals.

Or if they are very similar, finding the mean squared error between
the two signals
ie sum=  (a1-b1)^2 + (a2-b2)^2 .

Failing that, neural networks that can be trained to accept or reject?

The magnetic signals from cars - are these cars are moving - have you
factored in the different car velocities ?  Ie the same car might have
different signatures at different speeds etc.

```
```Errr, find the correlation?

If I remember correctly, remove the DC, multiply and sum the terms of
series A and B..
ie sum = a1*b1 + a2+b2 +.....
The sum will be proportional to the correlation between the two
signals.

Or if they are very similar, finding the mean squared error between
the two signals
ie sum=  (a1-b1)^2 + (a2-b2)^2 .

Failing that, neural networks that can be trained to accept or reject?

The magnetic signals from cars - these cars are moving - have you
factored in the different car velocities ?  Ie the same car might have
different signatures at different speeds etc.

```