They are point files with thousands of GPS fixes from cattle collars. However, I think I may be onto something with the following:
def calc_distance(shape, x0, y0):
point = shape.getPart(0)
X = point.X
Y = point.Y
d = math.sqrt(pow(X-x0,2) + pow(Y-y0,2))
return d
Expression:
calc_distance(!SHAPE!, 0, 0)
I will try it out today.