Angle value in results of IMAQ Find Straight Edges 3 VI

Hello everyone,

I'm working on a project for automated machine vision system using NI Vision.

One of the tasks is detect straight edge of the object. So, I'm using IMAQ Find Straight Edges 3 VI and I have question about results of this function.

For example, if I set method type of the detecting edge to "First Edge Rake" - function return explainable results, which are consistent with function description. But, if I set method type to "Hough Edge Rake", function returns strange value of edge angle. Moreover, if I make a little change in orientation settings, function returnes the same edge, but the differ angle in results.

So, could anybody explain what angle returned using Hough Edge Rake method?