[Paraview] origin of arc_length after application of "plot on intersection line" filter

[waku2005]

Dear all;

I have been calculated  a flow around a car in a duct.
I hope to know the distribution of pressure coefficient  on the body
surface, particularly on the typical intersection lines
in order to compare experimental results.

Please let me know about the "plot on intersection line"
After plotting the surface pressure, I had applied the " plot on
intersection line" filter to the surface plot.
I choose a y-normal intersection (y = 0, center of the body) and the
plot will be done to the X-Z surface intersection line.
I can see the 2-D plot of pressure (Vert. axis) vs arc_length (Hori.axis).

Then, my first question is where is the point of the arc_length == 0,
i.e.,  what are values of x and z at the arc_length == 0 ?
Second one is the calculation direction of the arc_length, because the
arc_length calculation can be defined CW or CCW  to the y-normal axis.

Best regards.
waku2005 at gmail.com