Angles have their own system that define both radians and degrees. I would like to create the necessary type for minutes (this is 1/60 of a degree). My first thought was to create a scale unit with degrees as the base type. I couldn't determine how to enter the scale of 1/60. The other option is to define a new base unit. I would think using the degrees base unit would be a good reference, but it uses an "INTERNAL ONLY" macro call "BOOST_UNITS_DEFINE_BASE_UNIT_WITH_CONVERSIONS". What should I use to create a unit type that will convert from degree minutes to just degrees?

Creating a scaled unit for minutes of arc is a good idea, but the base unit is already available in so you shouldn't have to go to the trouble other than defining the corresponding unit. Conversions to/from degrees should just work... Matthias