On Sunday, July 14, 2013 8:08:50 PM UTC+2, jfitch wrote:
Got a question: the Butterfly wind vector and the XCSoar wind vector (derived from Butterfly information) seem to disagree by 180 degrees. That is they point toward each other. XCSoar seems to believe it too, based on glide calculations. I am using the LX format output on the Butterfly. I am assuming the arrow on each is intended to point the direction the wind it blowing towards, I.e., a vector. From observation, the Butterfly appears to be correct, XCSoar 180 off. Has anyone seen this?

This sounds very much like the Butterfly firmware bug that was reported to the XCSoar bug tracker 4 months ago:

http://bugs.xcsoar.org/ticket/2660