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GPS internals: Difference between revisions
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<tt>gps/wp/wp[0]</tt> contains another waypoint, which varies depending on mode. For DTO and OBS modes, it is the position at the point the mode was entered; for LEG mode it is the previous waypoint in the route. In general the GPS is navigating ''from'' wp0, and ''towards'' wp1. | <tt>gps/wp/wp[0]</tt> contains another waypoint, which varies depending on mode. For DTO and OBS modes, it is the position at the point the mode was entered; for LEG mode it is the previous waypoint in the route. In general the GPS is navigating ''from'' wp0, and ''towards'' wp1. | ||
Due to unfortunate history, the route-manager ''also'' tracks a 'wp0' and 'wp1', but they do not correspond to the GPS labelling - the route-manager's wp0 is the active (current) waypoint, which corresponds to the GPS's wp1. (The route-manager's wp1 is the ''next'' waypoint, if one exists - the GPS code doesn't treat the next waypoint specially, for the moment) Changing either convention is judged to be too risky for existing aircraft, so they have been left as-is. | |||
In the future, when other kinds of leg exist, the active waypoint may not have a defined position; for example if the active leg is a hold, [[DME arc]] or procedure turn. | In the future, when other kinds of leg exist, the active waypoint may not have a defined position; for example if the active leg is a hold, [[DME arc]] or procedure turn. | ||