At a guess (and with only a quick glance at the code), it looks like all the GPS data is held in the linea[] buffer. indices[] seems to contains 13 integers which refer to the position in linea[] of each item of data.
So, the third item of data (which according to the switch statement is latitude) starts in linea[] at the position indicated by indices[2]. To extract it, you'd probably have to grab the bytes between indices[2] and indices[3].
As I said, I'm guessing a bit here so can only apologise if I'm wrong.