fixed issue #574
fixed issue #574

NMGRL/pychron,USGSDenverPychron/pychron,NMGRL/pychron,USGSDenverPychron/pychron,USGSDenverPychron/pychron,UManPychron/pychron,UManPychron/pychron,NMGRL/pychron,NMGRL/pychron,UManPychron/pychron,USGSDenverPychron/pychron,UManPychron/pychron