Feet Per Minute Conversion Question

On the Equator.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"JJ Sinclair" wrote in message
...

Navigational question for the day;
One minute of latitude = 1 nautical mile.
At what point on the earth does 1 minute of longitude = 1 nautical mile?

JJ Sinclair.

On Sun, 24 Aug 2003 14:38:07 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
wrote:

On the Equator.

Wrong.

There have been some geographical miles based on the equatorial
circumference, but I've never seen them called nautical miles. There
was one geographical mile equal to 4 minutes of arc on the equator, or
about 7.421 km; I have a copy of a map using these units.

Nautical miles have normally been defined to be some midrange,
midlatitude value for a minute of arc as you travel north-south along
a meridian.

At the equator, 1 minute of longitude is 1.001795 nmi.

But 1 minute of latitude (geodetic latitude, the kind normally used)
at the Equator is only about 0.9950 nmi.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"JJ Sinclair" wrote in message
...

Navigational question for the day;
One minute of latitude = 1 nautical mile.
At what point on the earth does 1 minute of longitude = 1 nautical mile?

JJ Sinclair.

It is at some place close to the equator, where the circumference of
the earth at that latitude is 40.0032 Mm, rather than the 40.007495 Mm
at the Equator (WGS-84 ellipsoid). A latitude close to the arccosine
of 40.0032/40.007495, or about 3½ degrees from the Equator either
north or south (a more exact value depends on which type of latitude
you use, as well as which ellipsoid you use to approximate this).

To help see this better, your "minute of longitude" at a latitude of
60 degrees would be about 0.50 nmi, and at the poles a
"minute of longitude" is 0 nmi. It is actually the minute of latitude
as you travel along a meridian (constant longitude) that most people
consider in evaluating the fit of a nautical mile to the Earth.

Now, at what point is one centigrade of latitude equal to one
kilometer?

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

Hey Gene, What kind of glider do you fly? Methinks you are a troll
and should leave this newsgroup alone with your misguided "superior"
knowledge of weights and measure. This is a newsgroup for soaring.

Gene Nygaard wrote in message . ..
On Sun, 24 Aug 2003 14:38:07 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
wrote:

On the Equator.

Wrong.

There have been some geographical miles based on the equatorial
circumference, but I've never seen them called nautical miles. There
was one geographical mile equal to 4 minutes of arc on the equator, or
about 7.421 km; I have a copy of a map using these units.

Nautical miles have normally been defined to be some midrange,
midlatitude value for a minute of arc as you travel north-south along
a meridian.

At the equator, 1 minute of longitude is 1.001795 nmi.

But 1 minute of latitude (geodetic latitude, the kind normally used)
at the Equator is only about 0.9950 nmi.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"JJ Sinclair" wrote in message
...

Navigational question for the day;
One minute of latitude = 1 nautical mile.
At what point on the earth does 1 minute of longitude = 1 nautical mile?

JJ Sinclair.

It is at some place close to the equator, where the circumference of
the earth at that latitude is 40.0032 Mm, rather than the 40.007495 Mm
at the Equator (WGS-84 ellipsoid). A latitude close to the arccosine
of 40.0032/40.007495, or about 3½ degrees from the Equator either
north or south (a more exact value depends on which type of latitude
you use, as well as which ellipsoid you use to approximate this).

To help see this better, your "minute of longitude" at a latitude of
60 degrees would be about 0.50 nmi, and at the poles a
"minute of longitude" is 0 nmi. It is actually the minute of latitude
as you travel along a meridian (constant longitude) that most people
consider in evaluating the fit of a nautical mile to the Earth.

Now, at what point is one centigrade of latitude equal to one
kilometer?

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

(JJ Sinclair) wrote in message ...
Navigational question for the day;
One minute of latitude = 1 nautical mile. At what point on the earth does 1
minute of longatude = 1 nautical mile?
JJ Sinclair

8-9 degrees north or south LAT where EW radius of curvature = NS
radius of curvature.

With screwy "geodetic" latitude that gps uses, FAI 6371km sphere
errors are even worse than if using geocentric latitude on ellipsoid.
I think pythagorean theorum with scale factors below would match
ellipsoid better than sphere does for gliding distances.

Someone please check these equations. The instrument display makers
may want to use an ellipsoid some day:

dist = pi/180*[delta Lat or Long in deg]*radius of curvature

radius of curvature NS:
a^2*b^2/(a^2*cos^2(Lat)+b^2*sin^2(Lat))^(3/2)

radius of curvature EW:
a^2/sqrt(a^2+b^2*tan^2(Lat))

Jonathan

p.s. check my equations against tiny EW or NS distances at various
lats using the FAI java calculator.

(JJ Sinclair) wrote in message ...
Navigational question for the day;
One minute of latitude = 1 nautical mile. At what point on the earth does 1
minute of longatude = 1 nautical mile?
JJ Sinclair

(Didn't read the question the first time, and answered "When does a
minute of lat = a minute of long?" instead.)

Second guess:

One minute of latitude equals 1.000000000 nm only at a single latitude
somewhere between 44° and 45° N (or S) latitude. (Don't expect it to
fall on an even minute.)
One minute of longitude equals 1.000000000 nm only at a single
latitude somewhere between 3° and 4° (N or S) latitude. (Don't expect
it to fall on an even minute.)

Morals:
1) Don't count on those ticks on the chart - you'll fall short : )
2) Don't move to the equator to find square lat/long grids.

Jonathan Gere

(Steve B) wrote in message . com...

How do you convert Kts per Sec / Meters per sec / Kilometers etc... to
Feet per minute

Knots per second would be a unit of acceleration, since knots are
already a unit of velocity. One knot is one nautical mile per hour.

I have two "older" gliders, each with 2 varios (4 varios total). 1
vario reads in feet per second, another in meters per second, another
in knots, and the last one in 100's of feet per second...

I have settled on thinking in terms of "knots" because 1) that's what
everyone else uses where I fly (so I can easily decipher thermal
strength callouts on the radio and so forth) and 2) for all practical
purposes 100 fpm is one knot, as others have correctly pointed out.

-Doug

Iwrote:
I have two "older" gliders, each with 2 varios (4 varios total). 1
vario reads in feet per second, another in meters per second, another
in knots, and the last one in 100's of feet per second...

Pardon me, that should read "100's of feet per *minute*..."

-Doug

How do I convert Meters/second to Leagues per Hour? I need the answer
to five significant digits.

I also need to convert wing loadings from Kg/square meter to
tons/acre.

Can I do the conversion in Winpilot?

tons/acre = Cos( furlongs/ weekend)
Jon.



"Liam Finley" wrote in message
om...
How do I convert Meters/second to Leagues per Hour? I need the answer
to five significant digits.

I also need to convert wing loadings from Kg/square meter to
tons/acre.

Can I do the conversion in Winpilot?

On 27 Aug 2003 10:54:05 GMT, John Lee
wrote:

Navigational question for the day;
One minute of latitude = 1 nautical mile. At what point
on the earth does 1
minute of longatude = 1 nautical mile?
JJ Sinclair

Nowhere! However on the equator 1 second of longitude
equals 1 nautical mile

That isn't any more correct now than when Bill Dean
claimed that
earlier in this thread. See my reply to his message.

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

Still looking Gene...... the other stuff is interesting
though