Christian Mayer writes: > Great that we've got a standard place for these properties now. > > But I'm really concerned that these values aren't in SI units. > > So most of the world (except the US and perhaps a few other countries) > can't use those units anymore without big research (aks somebody around > here what a 'slug' is... [*I* know it, but that doesn't count]).
I have no objection personally to doing everything in SI -- I'm Canadian, so I'm very used to metric. When we've had this discussion before, however, most developers were very strongly opposed to standardizing on SI internally, and it's certainly true that even in Canada (which switched to metric in the 1970s) we still use feet, inches of mercury, knots, and statute miles for aviation-related weather (but a Canadian ATIS broadcast *will* use celsius for temperature). In the end, I'm probably going to make the properties available in several flavours, so the main question will be what's used internally. It's not just a matter of SI vs. Imperial -- for example, for temperature we have to choose among Celsius, Kelvin, Fahrenheit, and Rankine, while for pressure, we have atmospheres, bar, mbar, inHg, inH2O, kgf/m^2, Pa, lbf/ft^2, mmHg, and many others. Yech. > If a FDM wants to use obscure units internally (e.g. because the > developers are use to them) that's their choice. But when we have > very universal data that a lot of people need (users, panel > programmers, ...) we should use an international standard. I agree with the principle, but note that the aircraft panel instruments give the altitude in feet, not meters, the altimeter will be calibrated for inches of mercury, not pascals, and the airspeed will be in knots (or possibly statute mph), not kph -- using SI internally will force a lot of conversions. I'm sure that there exist SI aircraft panels somewhere, but I have not yet seen photos of any in general aviation. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
