OpenCPN/OpenCPN — pull request #15 by tom-r (2012-07-08 06:44:30+00:00)
Title: Manual mag variation

Allows manual setting of magnetic variation

Allows manual setting of magnetic variation in options/GPS tab; is only used
when mag.variation is not available via NMEA (which is the case with my
Garmin GPS 152).
Without the mag.variation, you don't have the Heading indicator,
only the COG indicator; in other words: you don't see your drift ...
For reference see flyspray tracker #811