Here you specify the start and end coordinates for the lines within the 2D matrix, from which you want to extract profile data.
Specifying the line spacing is specifying how many points you want the line to be split in, e.g. how many points between "start point" and "end point".
If you have specified to extract some of the items as vectors, the points are not extracted in the exact coordinates on the line that you specified, but in points in between the grid points. e.g if you specified that you want a line going through the coordinates (j,k) in Figure 5.1, the program will calculate the vector components in the points P(j,k) and Q(j,k), which are afterwards projected on the line you specified.
Figure 5.1 Extraction of vectors
