From: John Denker [EMAIL PROTECTED]
Please do not write to me saying that SLP must equal QNH
when you are flying at sea level. That's true in that
narrow special case, but not representative of the
general case.
Supporting John's point:
In real world operations, even when flying at sea
On 02/15/2007 04:55 PM, Alex Perry wrote:
More generally: It is always very important to distinguish between the facts
that arise from the
simulation of the planet (such as SLP and variation), and the facts that
arise from simulation of
the airspace (such as QNH and VOR alignment).
Yes.
Dave Perry wrote:
On Mon, 2007-02-12 at 21:18 -0500, John Denker wrote:
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
On Mon, 2007-02-12 at 01:41 -0500, John Denker wrote:
On 02/11/2007 11:29 PM, Dave Perry wrote:
By the way, I agree that the current algorithm in altimeter.cxx is
wrong. This evening, I had time to look at your posted patch and I
think it would give the right hi.
It is, for now,
On Mon, 2007-02-12 at 11:33 -0500, John Denker wrote:
Overnight I thought of a non-disgusting way to optimize
the code. A new, muuuch better patch is now at:
http://www.av8n.com/fly/fgfs/altimeter.diff
The new patch gets the right answer without calling any
transcendental functions.
On Mon, 2007-02-12 at 17:24 -0700, Dave Perry wrote:
On Mon, 2007-02-12 at 11:33 -0500, John Denker wrote:
Overnight I thought of a non-disgusting way to optimize
the code. A new, muuuch better patch is now at:
http://www.av8n.com/fly/fgfs/altimeter.diff
The new patch gets the
On 02/12/2007 07:24 PM, Dave Perry wrote:
This looks really slick,
:-)
... why is this patch good above the troposphere ( 100,000 ft.)? It
should give the same answer as the last patch, only much more
efficiently.
The tabulated numbers come from a three-layer model, namely
layers 0
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
On 02/13/2007 12:11 AM, Dave Perry wrote:
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.
Yes, equation 8, but I don't even need to solve for h.
That's the
On Sun, 2007-02-11 at 00:22 -0500, John Denker wrote:
Both the Weather Conditions popup and the atis.cxx code rely
on the pressure-sea-level-inhg property and use it in ways
that the altimeter setting should be used.
This is at least a misnomer, and probably a misconception.
The altimeter
On Sun, 2007-02-11 at 08:02 -0700, Dave Perry wrote:
Have you looked for bugs?
I just looked at altimeter.cxx and altimeter.hxx. The
indicated-altitude-ft is the result of a LowPass (taking into account
the last altitude) of an iterpolation of a table created from an array
in altimeter.cxx. I
On Sun, 2007-02-11 at 00:22 -0500, John Denker wrote:
Both the Weather Conditions popup and the atis.cxx code rely
on the pressure-sea-level-inhg property and use it in ways
that the altimeter setting should be used.
This is at least a misnomer, and probably a misconception.
The
On 02/11/2007 01:42 PM, I wrote:
OK ... assuming by altitude they mean pressure altitude not true
altitude or absolute altitude or ...
Typo: I meant indicated altitude instead of pressure altitude.
Pressure altitude is something else yet again.
Sorry for any added confusion; this was a
Reference: Altimetry principles.
Lurid details including equations and derivations.
http://www.av8n.com/physics/altimetry.htm
-
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done
On Sun, 2007-02-11 at 13:42 -0500, John Denker wrote:
On 02/11/2007 10:02 AM, Dave Perry wrote:
So the altimeter setting is the same thing as the mean-sea-level
barometric pressure.
Huh? That does not follow at all. The quoted passage does not
say that at all.
Your own paper implies
On 02/11/2007 11:29 PM, Dave Perry wrote:
By the way, I agree that the current algorithm in altimeter.cxx is
wrong. This evening, I had time to look at your posted patch and I
think it would give the right hi.
It is, for now, restricted to the troposphere (36000 feet and below).
Extending
There is evidently at least one serious misconception in
the code that calculates atmospheric pressure, altimeter
settings, et cetera. This can be easily demonstrated:
Park at or near the threshold of runway 33 at Aspen
(KASE). Under standard conditions, observe that the
altimeter reads 7820 feet
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