Feet Per Minute Conversion Question

Gene, we aren't doing ballistics here; we only want
to get close enough for the eyeballs to do the proper
adjustments. For badge flights we try to exceed the
minimums enough to make up for instrument errors; for
record flights we must exceed the current record by
a percentage that should account for these relatively
minor distances.

It's nice that someone is turned on by all this precision;
in my mind it has all the usefulness of train spotting
with respect to practicality in soaring.

At 15:12 28 August 2003, Gene Nygaard wrote:
Maybe Eratosthenes still thought the Earth was a near-perfect
sphere,
when he made a fairly reasonable calculation of its
diameter Maybe
Columbus wasn't even aware of the true shape of the
poles.

But we've known about the flattening at the poles for
about four
centuries at least, probably longer than nautical miles
have existed.
Certainly since long before the French scientists in
the 1790s
designed the meter to be 1/10000000 of the distance
from the equator
to the North Pole.

We do, of course, have 360 degrees around the equator.
When we agree
on a starting point (e.g., the point where it crosses
the meridian
through Greenwich, England, the one most often used
now), any
particular place will always be the same number of
degrees from it.

We also have 90 degrees between the equator and either
pole. The
equator is always 0 degrees and the poles 90 degrees.
But in between,
there are at least three different ways of measuring
latitude:
geocentric latitude (the angle formed at the center
of the Earth),
geodetic latitude (the one normally used, the angle
formed between the
line normal to the tangent of the ellipsoid and the
axis of rotation),
and the angles used in the parametric formulas representing
an
ellipse. These don't agree with each other at any
place not on the
equator or the poles.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

In my line of work we speak of "measuring it with a micrometer, marking it
with a crayon, and then cutting it off with an axe".
Bob Korves

"Nyal Williams" wrote in message
...
Gene, we aren't doing ballistics here; we only want
to get close enough for the eyeballs to do the proper
adjustments. For badge flights we try to exceed the
minimums enough to make up for instrument errors; for
record flights we must exceed the current record by
a percentage that should account for these relatively
minor distances.

It's nice that someone is turned on by all this precision;
in my mind it has all the usefulness of train spotting
with respect to practicality in soaring.

At 15:12 28 August 2003, Gene Nygaard wrote:
Maybe Eratosthenes still thought the Earth was a near-perfect
sphere,
when he made a fairly reasonable calculation of its
diameter Maybe
Columbus wasn't even aware of the true shape of the
poles.

But we've known about the flattening at the poles for
about four
centuries at least, probably longer than nautical miles
have existed.
Certainly since long before the French scientists in
the 1790s
designed the meter to be 1/10000000 of the distance
from the equator
to the North Pole.

We do, of course, have 360 degrees around the equator.
When we agree
on a starting point (e.g., the point where it crosses
the meridian
through Greenwich, England, the one most often used
now), any
particular place will always be the same number of
degrees from it.

We also have 90 degrees between the equator and either
pole. The
equator is always 0 degrees and the poles 90 degrees.
But in between,
there are at least three different ways of measuring
latitude:
geocentric latitude (the angle formed at the center
of the Earth),
geodetic latitude (the one normally used, the angle
formed between the
line normal to the tangent of the ellipsoid and the
axis of rotation),
and the angles used in the parametric formulas representing
an
ellipse. These don't agree with each other at any
place not on the
equator or the poles.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

(Bob Kuykendall) wrote in message . com...
Earlier, Pat Russell wrote:

My vario is calibrated in megaparsecs
per millenium. Very handy.

I prefer cubits per jiffy for the vario, and furlongs per fortnight for the ASI.



Your altimeter is in fathoms?

Add one more, Bob.

Measure with a micrometer,

Mark with a crayon,

Cut on the safe side, with an axe,

Grind to fit!
JJ Sinclair

(Bob Kuykendall) wrote in message . com...
Earlier, Pat Russell wrote:

My vario is calibrated in megaparsecs
per millenium. Very handy.

I prefer cubits per jiffy for the vario, and furlongs per fortnight for the ASI.



Bob "" K.

Angstroms per picoseconds anyone?

On 28 Aug 2003 19:10:17 -0700, (Lennie the
Lurker) wrote:

Robert Ehrlich wrote in message ...
Gene Nygaard wrote:

On Thu, 28 Aug 2003 12:49:30 +0000, root
wrote:

Pat Russell wrote:

My vario is calibrated in megaparsecs per millenium. Very
handy.

According to my calculations, this should be near 0.5 mm/s.
You need a very big scale.

Try again. What do you think a millennium is? A parsec? The prefix
mega-?

1 Mpc/ka = 978 Gm/s, or about 3262 times the speed of light. He's got
bigger problems than you thought.

In other words, even one parsec (without the prefix) per millenium is
nearly 1 Mm/s (978 km/s). Thus 1 microparsec per millennium is equal
to a meter per second, within the precision many of you accept with
knots and the like.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

I just forgot the mega, I computed a parsec/millenium. Here is what I
did:

1 parsec is the distance of something having a parallax of 1 second, i.e.
the distance (from the sun) where the diameter of the orbit of the earth
is seen with an angle of 1 second. I don't remember this diameter but I
remember that the light coming from the sun needs 8 minutes to do that,
so the diameter should be 8*2*60*3*10^8 (diameter = 2*radius, 60 seconds
in a minute, speed of light 3*10^8 m/s) = 4800000000 m. 1 second is PI/(180*60*60)
radians, so 1 parsec is 4800000000/(PI/(180*60*60)), this is roughly 10^15 m.
A year is nearly 365.25 days, i.e. 365.25*24*60*60 seconds = 1980281535681600 s.
A millenium is 1980281535681600*1000 = 1980281535681600000 seconds or roughly
2*10^18 s. So a parsec/millenium is 10^15/(2*10^18) = 0.5*10^-3 m/s. A megaparsec
per millenium should be ~ 500 m/s. A huge unit for a vario in a glider, although
well under the speed of the light.

Well I was never good in calculations, so if there is a error, please point where.

the speed of light is 299759.6 km/s. the orbital radius is 149668992
km. Not exact, but close enough.

Wrong.

The speed of light is 299.792458 Mm/s. Exactly. That is
299792.458000000000000000... km/s, with as many zeros as you care to
add.

The astronomical unit is about 149.597870 Gm. Not exact, but close
enough--and different from your value by .05% or 1 part in 2100.
Yours is wrong in the 5th digit, and all the following ones are
garbage.




Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

Gene Nygaard wrote in message . ..

Yours is wrong in the 5th digit, and all the following ones are
garbage.

Once you go past the fourth digit, everything else in astronomy is
speculation. Ask me if I give a ****.

"George William Peter Reinhart" wrote in message ...
Troll = Ugly devil liviin' under a bridge, (see also motorcycle cops with
radar guns (usually under a bridge)).
Trolls = More than one ugly devil (also found in newsgroups)
Trolling = Fishin' with fake bait from a slow boat.
Cheers!


As used on the Internet (source = Whatis?com):

2) As a verb, the practice of trying to lure other Internet users
into sending responses to carefully-designed statements or similar
"bait."


I suspect that unless one's dictionary is very recent that the words
"hacker" and "spam" would also not be defined as they are now used on
the Internet, if they are defined at all.


-Doug Hoffman

Gene wrotethe
line normal to the tangent of the ellipsoid and the axis of rotation),
and the angles used in the parametric formulas representing an
ellipse.

I got a little lost in all that, Gene, but I figure it all amounts to about
half a mile (statute) in a 1000K flight. Anyone that doesn't plan their long
flight with at least a 5 mile cushion, is asking for trouble.
JJ Sinclair

On Sat, 30 Aug 2003 19:13:47 +0100, Mike Lindsay
wrote:

In article , Gene Nygaard
writes
On 27 Aug 2003 20:30:05 GMT, (JJ Sinclair) wrote:

John Lee wrote.
Nowhere! However on the equator 1 second of longitude
equals 1 nautical mileWe also have 90 degrees between the equator and either pole. The
equator is always 0 degrees and the poles 90 degrees. But in between,
there are at least three different ways of measuring latitude:
geocentric latitude (the angle formed at the center of the Earth),
geodetic latitude (the one normally used, the angle formed between the
line normal to the tangent of the ellipsoid and the axis of rotation),
and the angles used in the parametric formulas representing an
ellipse. These don't agree with each other at any place not on the
equator or the poles.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

Hmm, interesting...

What would the error be over, say 500km, if you used geocentric instead
of geodetic measurement?

In other words, does it matter?

If you are measuring the difference between two points, it will make
no difference whatsoever--assuming that you do the calculations
properly for the angles you are using. It's just that those two end
points will be at different latitudes, depending how you measure that
latitude.

That assumption has no guarantee of likelihood, if you are unaware
that there are different ways to measure latitude. It's sort of like
the Mars Climate Orbiter-turned-Crash-Lander. Those NASA engineers
could have converted pound force seconds to newton seconds--only
problem was, they didn't realize that they should be doing so.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/