Looking for a math wiz!

"d&tm" wrote in message
...

"Stefan" wrote in message
...
d&tm schrieb:

if you know HDG ( ie where you are pointing), GS and TAS then there is
only
1 possibility for the wind speed and direction.

Actually, there are two.

I give up, can you please explain how there can be 2 ?


There are two possible situations for the wind correction. You do not know
the direction of the correction for wind ( i.e. is the plane crabbing left
or right to compensate for x-wind) you only know the magnitude (wind speed).
Think of the triangle that is formed by vectors on the e6b. Without the
direction, you have an ambiguous answer, looks like two similar triangles, a
lefty and a righty.
Someone else could probably explain this better, that's the basic idea.

Mike

"Michael Ware" writes:
"d&tm" wrote
"Stefan" wrote
d&tm schrieb:

if you know HDG ( ie where you are pointing), GS and TAS then there is
only 1 possibility for the wind speed and direction.

Actually, there are two.

I give up, can you please explain how there can be 2 ?

There are two possible situations for the wind correction. You do not know
the direction of the correction for wind ( i.e. is the plane crabbing left
or right to compensate for x-wind) you only know the magnitude (wind speed).
Think of the triangle that is formed by vectors on the e6b. Without the
direction, you have an ambiguous answer, looks like two similar triangles, a
lefty and a righty.
Someone else could probably explain this better, that's the basic idea.

And a simple explanation of the whole process is that
the wind triangle has three (vector) components:
heading, course, and wind. The vector sum of heading
and wind gives course which is the problem that pilots
are accustomed to solving. Rearranging the equation
so as to compute wind given heading and course is not
at all difficult. The law of cosines allows determination
of the third side of a triangle given two sides and
the included angle. The law of sines allows determining
the other two angles given the three sides. There is no
left/right ambiguity given the course and heading.

Can you email that to me also.




"d&tm" wrote in message
...

"Chad Speer" wrote in message
ups.com...
Okay, I know I've seen a lot of engineers and technical folks on here.
I have a complex math problem relating to the classic wind triangle
that I posted on sci.math and received little response. I don't know
if they're stumped or just not interested. :-)

Here is a copy of my original post and the only useful response I
received. Anyone have a solution?

(For the controllers here, this is an enhancement we are trying to add
to the Falcon program that centers will see next year, which was
developed by a controller here at ZKC.)


Chad Speer
PP-ASEL, IA
ATCS, Kansas City ARTCC



************************************************** *
************************************************** *

My original post:
*****
I am helping someone with a program that estimates wind speed and
direction using radar data from aircraft. I need help finding a
formula that can determine the wind speed and direction when given the
following information for multiple aircraft:

direction of travel
speed across the ground
speed through the air

The direction of travel and the speed across the ground are taken from
the radar data. The speed through the air is taken from the pilot's
flight plan. We're air traffic controllers trying to improve our
training tools, so we get access to all the goodies.

I know that with information from just one aircraft, the possibilities
are endless for the wind speed and direction. I think it is possible
to use the same data from two or more aircraft to determine the wind
speed and direction.

I thought I could come up with a formula to solve this, but the need to
reference everything to north in order to achieve actual directions
instead of just angles took it way above my head.

snip

Chad
if you know HDG ( ie where you are pointing), GS and TAS then there is
only
1 possibility for the wind speed and direction. these can be calculated
from the cosine rule. If you know the cosine rule and the sine rule for
triangles you can calculate a lot of things.
to apply both of these rules draw yourself a little triangle and mark the
sides small a,b and c.
then mark the angles capital A,B and C where angle A is opposite side a
and angle B is opposite side b.
cosine rule a^2 = b^2 +c^2 - 2bc cos( A)
sine rule a/sin A = b/sin B = c /sin C

in the case of the NAV triangle

WS= SQRT( GS^2+TAS^2 =2*GS*TAS*cos(HDG-TR))
where WS= windspeed
GS = ground speed
TAS = airspeed
HDG = heading(where you are pointing)
TR = track ( where you are going)

If you want I can email you an excel spreadsheet that has this already
coded. you just enter your TAS, GS and HDG and it will give you the WS
and
Wind direction.

Terry
PPL

[followups set to r.a.piloting]

In rec.aviation.piloting Chad Speer wrote:
Anyone have a solution?

I don't know what the solution is but I can certainly admire the
problem.

Actually, I think I pretty much agree with the one response you posted,
in part:

a)1 aircraft -- system not solvable.
b)2 aircraft -- system has one solution, but I'm too lazy to do the
algebra.

I worked out a little of the algebra for b) and the equations just
seem to be getting longer and longer instead of heading for a solution,
so I stopped.

c)3 or more aircraft -- system is overspecified, and some least
squares approach should give a solution.

I may be saying the same thing he is, but here is possibly another way
to look at case for 3 or more aircraft. If you know how to solve the
problem for 2 aircraft, and you have more aicraft than that, you can
pick any two and solve the problem for those two aircraft, yielding
a wind speed and direction. Then you can pick a different pair of
aircraft and solve the problem again -- you should get something close
to the same answer you got the first time. If you do this for all the
possible pairs of aircraft, you will _probably_ end up with a range of
answers that are somewhat grouped around a middle point. This does
result in a lot of calculations - 380 pairs for 20 aircraft or 9900
pairs for 100 aircraft - but this is the kind of thing computers are
good at.

It has been my experience that wind direction and speed won't vary
too much over distance, but may vary EXTREMELY with altitude.

I definitely agree with this. When you are picking pairs of airplanes,
it may be helpful (in terms of coming up with meaningful numbers) to
pick ones that are sort of close to the same altitude.

[from earlier in your post:]
I have a complex math problem relating to the classic wind triangle
that I posted on sci.math and received little response.

Here is some complete speculation on why it didn't get much response:

1) The folks there saw the magic words "air traffic control" in your
post and figured that if they helped you with it, they'd probably
get sued any time a plane crashes for the next 50 years.

2) The folks there saw the magic words "air traffic control" in your
post and figured out that you really do work for the FAA and
therefore have unlimited amounts of money and should give them a
grant to study this problem, rather than them answering for free on
Usenet.

Understand that I'm not saying that you shouldn't have said the magic
words - it's often quite helpful to understand the basic problem
somebody is trying to solve. And maybe neither of my speculations are
accurate.

Some other ideas on places to ask for help:

The halls of academentia. Go down to UMKC, find the math department,
and see if one of the professors can help you. They might also refer
you to a grad student who is good at turning food into solved math
problems. One minor problem with this is timing - they may have
all bugged out for the holidays.

NWS/NOAA. They might have solved this problem themselves at some point
and might be able to give you some code. My first two guesses at where
to try would either be the regular office in Pleasant Hill, MO, or the
Severe Storms Lab in Norman, OK.

You probably know about this, but you can cheat by pointing a radar
straight up and letting it figure out what the winds are doing:
http://www.profiler.noaa.gov/npn/pro...p?options=full
But it sounds like you might be working on a (partially?) "canned"
training scenario and current real-world data is not exactly what
you need.

I hope this helps!

Matt Roberds

Matt wrote:

*****
If you know how to solve the problem for 2 aircraft, and you have more
aicraft than that, you can pick any two and solve the problem for those
two aircraft, yielding a wind speed and direction. Then you can pick a
different pair of aircraft and solve the problem again -- you should
get something close to the same answer you got the first time. If you
do this for all the possible pairs of aircraft, you will _probably_ end
up with a range of answers that are somewhat grouped around a middle
point. This does result in a lot of calculations - 380 pairs for 20
aircraft or 9900 pairs for 100 aircraft - but this is the kind of thing
computers are good at.
*****

Exactly how I hope this plays out.

*****
When you are picking pairs of airplanes, it may be helpful (in terms of
coming up with meaningful numbers) to pick ones that are sort of close
to the same altitude.
*****

I didn't specify in my original post because I didn't expect the
question to be raised, but we will be using aircraft within a 2000 foot
window. At the higher altitudes, that rarely involves a difference of
more than a few degrees and maybe six knots of wind.

*****
1) The folks there saw the magic words "air traffic control" in your
post and figured that if they helped you with it, they'd probably get
sued any time a plane crashes for the next 50 years.
*****

I hadn't considered that. Hell, even *I* don't trust the FAA. :-)

*****
2) The folks there saw the magic words "air traffic control" in your
post and figured out that you really do work for the FAA and therefore
have unlimited amounts of money and should give them a grant to study
this problem, rather than them answering for free on Usenet.
*****

I wish I could offer someone money. This whole system was designed by
a controller who realized the data was just sitting there and decided
to make something useful with it. Now, it's being deployed nationwide.
If the FAA really gets involved, this will be a useless program. Never
fails.

I really have no involvement in this. He briefed me on his work and I
told him I thought I could produce a formula for the wind. We'll see.
I may have bitten off too much. :-)

*****
The halls of academentia. Go down to UMKC, find the math department,
and see if one of the professors can help you. They might also refer
you to a grad student who is good at turning food into solved math
problems. One minor problem with this is timing - they may have
all bugged out for the holidays.
*****

This was my original thought. We even have an aerospace engineering
program nearby (University of Kansas) where I could probably shame
someone into a solution. "The guys in the math department said you
couldn't handle the trigonometry."

I really like the open discussion of Usenet and would love to make this
solution an eternal part of rec.aviation. If that doesn't happen, I'll
bribe some grad students...

*****
NWS/NOAA. They might have solved this problem themselves at some point
and might be able to give you some code. My first two guesses at where
to try would either be the regular office in Pleasant Hill, MO, or the
Severe Storms Lab in Norman, OK.
*****

Now there's an idea I will consider. We even have meteorologists on
staff who could probably grease some wheels there.

Thanks for the discussion!

Chad Speer
PP-ASEL, IA
ATCS, Kansas City ARTCC

"Chad Speer" wrote in message
ups.com...

Chad Speer
PP-ASEL, IA
ATCS, Kansas City ARTCC



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snip

direction of travel
speed across the ground
speed through the air


If you can get heading also, it is a fairly simple equation as others have
posted.

Danny Deger