I previously had a similar question where I had to define my own unit that may be helpful to you:
http://stackoverflow.com/questions/4322133/converting-units-in-boost-units-from-angular-velocity-to-degrees-per-second

Cheers!
Andrew Hundt


On Wed, Feb 20, 2013 at 10:11 PM, Steven Watanabe <watanabesj@gmail.com> wrote:
AMDG

On 02/20/2013 06:32 PM, Ryan wrote:
> Boost Community,
>
> I'm trying to create a custom velocity unit.  I would like to create a unit
> that is in nautical miles per hour to represent my speed value.  If I use
> pound_force.hpp as an example of units with more than one dimension I can
> create the following.
>
> BOOST_UNITS_DEFINE_BASE_UNIT_WITH_CONVERSIONS(metric,
> nautical_mile_per_hour, "nautical mile per hour", "nmi h^-1", factor,
> si::velocity, ???);
>
> If this is the right track, what id would I use and how do I know that it
> is unique?
>
> This seems forced.  I would rather define this unit in terms of meters per
> second.  Nautical miles is already in terms of meters and hours is also
> defined as a scale of seconds.  Can I somehow use these two already defined
> units to create the new unit?  How would I do this?
>

You probably don't need to define a base unit.
Just use:

typedef decltype(
  nautical_mile_base_unit::unit_type() /
  hour_base_unit::unit_type()) nautical_miles_per_hour;

In Christ,
Steven Watanabe
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