Hi John, Thanks for answering my questions. I did not realize the interpolation table was for the first three layers.
On Mon, 2007-02-12 at 21:18 -0500, John Denker wrote: > > The tabulated numbers come from a three-layer model, namely > layers 0 through 2 as defined in the table at the front > of this reference: > http://www.av8n.com/physics/altimetry.htm > See also references therein. I did not realize the interpolation table was for the first three layers. I can see how you generate a table that gives PA and C(s) for layers with nonzero lapse rate. I assume you use equation (8) solved for h to generate the table when lamda = 0. In this case, how do you account for S = 29.92 being different from Pb? It seems to me that Equation (8) will give us neither PA nor the Kollsman correction. > Yesterday's effort used only layer zero, which is why it was > valid only within the troposphere, 36000 ft MSL and below. > > [snipped several more questions, all with the same answer] Agreed, thanks again. > I also haven't changed my mind about the following: > > > What I am proposing is to create a C++ function (say height_ft) that has > > two arguments, P0 and P1 that does the interpolation in John's new patch > > using his constants. > > That is the same spirit as what I was suggesting in the opening > paragraphs of: > http://www.av8n.com/fly/fgfs/README.altimetry.html > It is even more important that all those approximating PA or C(S) use one function since the constants change at the boundaries between the layers in your function but not in kap140.nas and the encoder model. By the way, I need to rewrite the Kollsman correction used in kap140.nas. While reading in detail your altimetry.hml, I was using a spread sheet to compare your equations and constants with what was done for the altitude capture in kap140.nas. I want to replace the partial differential approximation with at least the version of C(S) from your first patch. But if the plan is to do the one-for-all C++ function, I would really prefer to wait and use that. For that to work well above the Tropopause, Roy will have to use that function in the encoder. > > When will you put this in cvs? > > Ha, funny joke. > If you want to do the one-for-all function, the sooner the better. I hope I did not offend by poking, reading, and questioning. I know I like it when someone reads seriously and carefully what technical papers I have written. Thanks again for the effort. It took a while for your vision to sink in. Regards, Dave ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
