# Using laser_scan_matcher output

I would like to have a confirmation on my understanding in order to use the output of `laser_scan_matcher(lsm)`

in a correct way. Kindly refer to the provided figure(sorry for providing a mere sketch). For convention, please assume any subscript of 1 refers to the previous data(means x1= previous x value from `lsm`

and so on). Likewise, subscript of 2 refers to the current data. P1 and P2 is the position of the x and y values returned by pose2D of the previous and current values respectively that have been mapped into a `cartesian`

coordinate.

My questions are:

Is that correct the representation of variables in the context of

`lsm`

?Calculation of Q:

i) Either:

`Q = sqrt[(x2-x1)² + (y2-y1)²] x sin(theta1) OR Q = sqrt[(x2-x1)² + (y2-y1)²] x sin(theta2) OR Q = sqrt[(x2-x1)² + (y2-y1)²] x sin(theta2-theta1)`

ii) OR Q = x2-x1

This sounds like a fundamental math problem, but with respect to the values returned by `lsm`

makes me confused. Perhaps someone who is experienced using the package or preferably the author himself can give some comments regarding this.

In my opinion, the correct one should be Q = sqrt[(x2-x1)² + (y2-y1)²] x sin(theta1), but I don't know if this one is correct or not in this regard.

Thanks in advance.

EDIT: