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GPS internals: Difference between revisions
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==Concepts== | ==Concepts== | ||
The code computes basic positional information, derived from FG's knowledge of the aircraft position (i.e the /position properties). There is no attempt made to accurately simulate GPS position calculation - in the future an error function will be used (optionally) to reduce the accuracy of the GPS indicated position. | The code computes basic positional information, derived from FG's knowledge of the aircraft position (i.e the <tt>/position</tt> properties). There is no attempt made to accurately simulate GPS position calculation - in the future an error function will be used (optionally) to reduce the accuracy of the GPS indicated position. | ||
From the indicated position, many other values are derived - ground track, speed, vertical speed, odometer and so on. All these values can be seen in the basic /gps property tree, and are hopefully self-explanatory. | From the indicated position, many other values are derived - ground track, speed, vertical speed, odometer and so on. All these values can be seen in the basic /gps property tree, and are hopefully self-explanatory. | ||
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The GPS has a simple command system - it expects the properties under <tt>gps/scratch</tt> to be populated with some parameters, and then a command property to be set. Information is also returned via the <tt>gps/scratch</tt> properties. For example, to go direct to a waypoint, it must be loaded into the scratch, and a 'direct' command executed. To find the nearest VOR, set <tt>scratch/type</tt> to <tt>vor</tt> and execute a <tt>nearest</tt> command. The scratch will be updated with information about the result (if one was found) - and then a 'direct' or 'obs' command can be executed to use the waypoint. | The GPS has a simple command system - it expects the properties under <tt>gps/scratch</tt> to be populated with some parameters, and then a command property to be set. Information is also returned via the <tt>gps/scratch</tt> properties. For example, to go direct to a waypoint, it must be loaded into the scratch, and a 'direct' command executed. To find the nearest VOR, set <tt>scratch/type</tt> to <tt>vor</tt> and execute a <tt>nearest</tt> command. The scratch will be updated with information about the result (if one was found) - and then a 'direct' or 'obs' command can be executed to use the waypoint. | ||
==Command List== | ==Command List== | ||