Laser gyros do indeed behave the way that the wiki page describes. Mechanical gyros, such as you find in light aircraft, have other drift sources that are considerably larger than the diurnal one. And, since the aircraft tend not to move far from their home latitude, there is an attempt by mechanics to adjust the gyro for zero net drift rate (on average).
The purpose of implementing the drift in FlightGear is for operational realism, more than scientific accuracy, and therefore the drift value is designed to make the gyro compass be inaccurate if the light aircraft pilot does not reset it regularly. If you want to include the sin(lat) term, be sure to add a flag so we can distinguish between the laser and mechanical variants. On Wed, Jan 14, 2009 at 5:43 PM, jean pellotier <jean.pellot...@wanadoo.fr> wrote: > hi, doing some nav with the pa24-250, i found the gyro compas drift was > always -15°/hour. > > I never went in a real aircraft except as passenger, but if i refer to > this page: > > http://en.wikipedia.org/wiki/Heading_indicator > > Shouldn't drift be related to the sin(lat), and opposite sign in the > southern hemisphere? > > I think the relevant code is in instrumentation/heading_indicator.cxx, > line 77: > > offset -= dt * (0.25 / 60.0); // 360deg/day > > but i don't know c++, so can't propose a patch. > > cheers > > jano > > > > > > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by: > SourcForge Community > SourceForge wants to tell your story. > http://p.sf.net/sfu/sf-spreadtheword > _______________________________________________ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
