make both plong and slong positive within pmag.vgp_di
make both plong and slong positive within pmag.vgp_di

lfairchild/PmagPy,Caoimhinmg/PmagPy,Caoimhinmg/PmagPy,lfairchild/PmagPy,lfairchild/PmagPy,Caoimhinmg/PmagPy