[Flightgear-devel] Typical NAV system errors

[Thorsten R. <tho...@sc...>]

I've now managed to streamline a first version of state vector propagation  
during Shuttle approach. I've used the following error estimates (I'd be  
obliged if people who have some more experience can eyeball and check  
them):

* for a gyroscopic inertial guidance system I found in several places  
drift rates of ~ 2 miles/hour. I've modeled that via random noise on the  
accelerometers, leading to velocity errors and hence accumulating position  
errors.

* for TACAN, I found as figures of merit quoted 0.5 deg in azimuth, 0.2 %  
in range with a minimum of 0.1 miles range error

* for the Microwave anding system some 20 ft horizontally and 5 ft  
vertically

* for barometric altitude measurements, instrumentation errors of 80 ft at  
10.000 ft altitude are apparently considered acceptable by the FAA, I've  
used an error range of 50 ft every 10.000 ft (plus whatever the  
calibration error to ground pressure is, but that's not a range but an  
offset).

If anyone has better numbers, I'd be much obliged to know.

Best,

* Thorsten