0.02 inches is a very short vector head - can you even see it? And +a180 would not even create a triangular head since your apex angle is 180. I should add an error message for that . Since I dont know what your region and projection is it is hard to tel if 30 km is the right scale and if it is a geographic plot (i.e., with geovectors) or a Cartesian plot (with Cartesian straight vectors).