I came up with an answer to my own challenge: In the real world there are two types of encoding altimeters:
I) The so-called blind encoders are basically just encoders. Their *only* output is digital and quantized. These can be made non-blind by wiring them to a display, but the display will necessarily exhibit quantization steps. II) There is a second type of instrument that is primarily a plain old steam-gauge type altimeter, producing a fully analog non-quantized display in the time-honored way ... plus an encoder disk attached to the mechanism. The analog display is unquantized, while the digital output is quantized. Therefore the <quantum> configuration option in my altimeter.cxx is ambiguous. In case (I) the quantization should affect the indicated output, while in case (II) it shouldn't. 1a) Arguments as to which behavior should be preferred should not be based on what the autopilot needs. The autopilot is already so complicated that adding the one line needed to perform the quantization within the autopilot -- not within the altimeter -- is IMHO clearly the right way to go. Code is incomparably more expressive than xml, and can easily resolve the ambiguity whichever way is desired. 1b) I would also point out that writing a stepless indicated output to the property tree and then writing a stepped pressure output to the property tree makes it impossible to calculate the Kollsman shift by subtraction. So this -- in combination with autopilot code that does not do its own Kollsman calculation -- is a self-inconsistent combination. 2) So the discussion comes down to ultra-simple xml-only instruments. We already have a way of producing a stepless indicated altitude output (i.e. the ordinary altimeter object with no quantization). Therefore if the quantization feature is to have any nontrivial value, it should produce stepwise indicated altitude outputs, such as would be seen in certain "backup altimeter" displays. This sounds to me like two solid arguments why if the encoder writes an indicated altitude at all, it should be based on the pressure altitude (quantization and all) plus a simple Kollsman shift. That's how I originally coded it. Now I know why I coded it that way :-). ------------------------------------------------------------------------- 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
