Carlson Field can use an external Light Bar for determining elevation differences and centerline offsets.
Light Bars can indicate whether your current position is in cut,
fill or on-grade when set vertically. When set horizontally, Light
Bars can give centerline left/right offsets. Currently Carlson
Field supports a light bar made by Apache, as well as by Mikrofyn,
that has arrows for up/down, or left/right, and a row of lights for
on-grade. The Light Bar must be connected to a separate serial port
than the GPS.