RE: "How Vikings Might Have Navigated on Cloudy Days" (Full Version)

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Vendaval -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/13/2007 4:20:49 AM)

Popeye, would you please explain the "mercator projection"
and the "gnormonic projection".
 
Thank you,
 
Vendaval

quote:

ORIGINAL: popeye1250
When you fly from Boston to Europe say the planes go up over canada and within a few hundred miles of Iceland kind of "hugging the coast" in "great circle sailing."
On a mercator projection that would look like "circular" flying but on a Gnomonic projection it would look like a straight line from point to point due to the curvature of the earth.



thompsonx -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 8:38:43 AM)

quote:

ORIGINAL: Vendaval

Popeye, would you please explain the "mercator projection"
and the "gnormonic projection".
 
Thank you,
 
Vendaval

quote:

ORIGINAL: popeye1250
When you fly from Boston to Europe say the planes go up over canada and within a few hundred miles of Iceland kind of "hugging the coast" in "great circle sailing."
On a mercator projection that would look like "circular" flying but on a Gnomonic projection it would look like a straight line from point to point due to the curvature of the earth.


Vendaval:
If you look at most maps of the world you will note that the parallels of latitude are not equally spaced, they become farther apart as you aproach the poles,this is a mercator map.  If you look at a globe you will notice that the lines of latitude are equally spaced. If you were to unwrap the map off of the globe and lay it flat it would appear as a series of orange peals sliced off of an orange (pointy at the top and bottom and connected at the center) this is a gnomic map.
If you were to take a string and lay it on a globe between any two points (clearly the shortest distance) and then transfer that line to a mercator map it would appear as a curved line.
thompson



mnottertail -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 8:43:44 AM)

This concept being a fundamental building block of Einsteins Relativity, for anyone who cares.  (Curvature of space)




FukinTroll -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 9:56:05 AM)

I thought Einstein’s theory of relativity was if you fuk your sister you would have a mutant.



popeye1250 -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 12:21:32 PM)

quote:

ORIGINAL: Vendaval

Popeye, would you please explain the "mercator projection"
and the "gnormonic projection".
 
Thank you,
 
Vendaval

quote:

ORIGINAL: popeye1250
When you fly from Boston to Europe say the planes go up over canada and within a few hundred miles of Iceland kind of "hugging the coast" in "great circle sailing."
On a mercator projection that would look like "circular" flying but on a Gnomonic projection it would look like a straight line from point to point due to the curvature of the earth.



Vendaval, sure, a "Mercator" projection on a nautical chart would look much like a street map, everything where it's supposed to be, used for smaller distances.
A "Gnomonic" projection on a nautical chart would be for very large distances, i.e. it would have Europe and the U.S. on the chart but it also accounts for the curvature of the earth so it looks "distorted" like if you were to peel off the paper on a globe.
If you drew a straight line on a "Gnomonic" projection and transferred that line to a "Mercator" projection it would look "curved."



Vendaval -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 1:48:25 PM)

Thank you both for the explanation, thompson and popeye.  [:D]



popeye1250 -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 1:50:20 PM)

P.S. if you've ever flown cross country or to Europe or Asia you might have noticed that the pilot will "change course" 2 or three times during the flight.
He's actually flying in a straight line!
The course changes are to compensate for the curvature of the earth.



Vendaval -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 1:56:14 PM)

Yes, makes perfect sense.  The exact terminology was unfamiliar
to me.  Always good to learn something new about the world from
someone with different experiences.



popeye1250 -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/14/2007 9:11:36 PM)

Well, I went to Navigation school when I was in the U.S. Navy.
It was pretty interesting learning all that type of stuff.
Out at sea we'd "shoot stars" with a sextant to find out where we were.



Vendaval -> RE: "How Vikings Might Have Navigated on Cloudy Days" (3/15/2007 1:04:57 AM)

My older brothers were both in the Navy.  The eldest was in
between Korea and Vietnam and did not have to serve
in combat situations.  The next eldest served during Vietnam
and saw combat.  He still has a hard time talking about what
happened when he was there.



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