What I'm trying to do is basically plot a rectangle on a runway that goes parallel with the runway.
When I start out everything works as expected:
But what I notice is that as I go further down the runway it varies significantly from the centerline as we see in the end of my rectangle:
This is not what I would expect, as I would expect the centerline to continue to match the runway centerline, or at least be closer.
My calculation for the points to plot is rather simplistic, as it is just the runway heading +/- the magnetic variation and it leaves me with this result. So my question is, is there anything else in my calculation I am missing in order to get this to be more precise?