[Proj] Re: Distance measured in Mercator projection

[strebe at aol.com]

If you assume a spherical earth, the length of a meter on the Mercator equatorial aspect is

1m / cos (phi)


 
where phi is the latitude and "cos" is the cosine function. Be careful to set the calculator to degrees or else to convert the latitude to radians. The calculation is more complicated on an ellipsoidal earth.

Regards,
-- daan Strebe



 

-----Original Message-----
From: Shannon Scott <sscott at locationinc.com>
To: Proj at lists.maptools.org
Sent: Wed, 9 Jul 2008 10:52 am
Subject: [Proj] Distance measured in Mercator projection









Hello,?

Please forgive my ignorance, I know very  little about map projections.  
I apologize if this list is not the appropriate place to post this question.?

If I understand correctly, in the Mercator projection, 1 unit of space 
is equal to 1 meter at the equator.?

As you move away from the equator, the longitudinal lines are stretched 
to make the lat and long intersect at 90 degree angles.?

How would I calculate the length in meters of 1 unit of space in the 
Mercator projection at a specific latitude??

Any advice of pointers are appreciated.?

Thank you.?

Shannon?
?


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