On 02/25/2007 07:06 PM, Dave Perry wrote: >> Summary proposed compromise: >> 1) Use an encoder instantiation (altimeter[1]) with quantum = 10 as well >> as altimeter[0] with quantum = 0.
Yes, that seems entirely reasonable. >> 2) Leave the 5 new lines to allow unambiguous service to autopilot use >> of the encoder. How about 2') Have the autopilot calculate the Kollsman shift on its own. > At the start of this discussion, I thought you wanted just one model of > the atmosphere. So it is a bad idea to have each autopilot use it's own > model. Users are going to want to ignore different returned values for > different instantiations for "realism" reasons. But a real autopilot *does* have its own model ... not a model of the real atmosphere, but an ISA-model atmosphere (or, more precisely, a Kollsman-model atmosphere). Ditto for real altimeters. If you want to start with the canonical Kollsman model and then depart from it as a model of realistic instrumental imperfection, that's entirely reasonable. What was not reasonable was the previous altimeter, that used an algorithm bearing no known resemblance to reality, and was off by hundreds of feet under some perfectly ordinary conditions. > .... means the > kap140.nas has to retrieve the value it cannot have in reality > (indicated altitude) and wants to approximate from values it does have > (PA and baro shift), The real KAP does not have access to an oracle of any kind that will perform the Kollsman calculation for it. Arguing about which type of oracle is "more realistic" is an argument about members of the null set. Not the sort of discussion we ought to be having. The exact FAA-approved Kollsman calculation is well understood and easily implemented in nasal code. I know I previously pointed out that it was possible to use the altimeter as an oracle ... but that was before I realized how seriously people were worried about values "it cannot have in reality". If you care about reality at that level, doing the Kollsman calculation within the autopilot code is the only realistic option. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel