Bulge Factor

The BULG attribute is unique to the VRTX element, and is the ratio of the maximum departure of the arc from the chord joining two VRTXs to the chord half-length. It is positive when the span lies to the right of the chord when viewed in the direction VRTX1 to VRTX2, negative when it lies to the left. A straight span has a BULG of 0, a counter-clockwise semicircle a BULG of 1.0, and a clockwise semicircle a BULG of -1.0. BULG is not normally set explicitly, but indirectly by the SPAN command.