One that old would certainly not represent the performance of current devices....no offense to Chris, who, among other things is the creator and maintainer of NAR's Contest Manager software (which, when given the launch time temperature, does the calculation I mentioned above as part of the data entry process).There is a NAR R&D report by Chris Kidwell from when he flew a mess of altimeters in a rocket around 20 years ago. A little searching ought to turn it up.
So that leaves the quality of the sensor used and the filtering of spurious data (the "secret sauce" I mentioned earlier). They all should be using the same equation...Not conclusive but I have had customers fly Marsa's with MW, Perfectflite and Ravens and they all reported the same apogee altitude. So I am guessing those 3 are using the same SAM pressure to altitude equation. Pressure to altitude equation is pretty much 'settled science' by now.
Don't know about various GPS (or Glonass or whatever) devices. I presume they have to have some kind of onboard data capture/filtering/recording software as well, so there is room, I would think, for some minor variation at least between devices. But I don't know that.Oh, yes...I recall your Apogee Newsletter article...and without any prior knowledge of the requirements for flight triggering on my part, my "static" (non-flight) test proposal seems undo-able at this point. However, what I'm trying to understand is the amount of repeatability, if any, there is from one altimeter mfg to the other at any given altitude...I guess we'll never know....but we certainly can with GPS from mfg to mfg.
So the choice comes down to cost, precision, repeatability and accuracy (GPS) versus (baro)...all comments are welcome.
I've got LOTS of multi-manufacturer altimeter flights over the years....I just cite one particular one in the Apogee article (and in the NAR Member Guidebook). What I don't have are lots of multi-device flights much above 1000 feet, since I'm pretty much an LPR kind of guy.
Since I've been talking about it, here's the comparison graph (well, a .jpg version of it) that's in the Apogee Peak of Flight article. I've sent a version of this without the Adrel trace to go into the online version of the NAR Member Guidebook altimeter article (I don't talk about the Adrel in the Guidebook piece). This flight, for those who are keeping score, took place at Sixty Acres Park in Redmond, Washington. Per the data stored by the app for AltimeterThree, it took place at 2:14 PM from a point just a little south and east of the center of the north field at that park. I do not know (and don't really care) what the precise MSL altitude of my launch pad was that day.