NAME:
rphi_to_dl_2d
PURPOSE:
convert Galactocentric radius and azimuth to distance and Galactic longitude
INPUT:
R - Galactocentric radius
phi - Galactocentric azimuth [rad/deg if degree]
KEYWORDS:
degree= (False): phi is in degrees rather than rad
ro= (1) Galactocentric radius of the observer
phio= (0) Galactocentric azimuth of the observer [rad/deg if degree]
OUTPUT:
(d,l); phi in degree if degree
HISTORY:
2012-01-04 - Written - Bovy (IAS)