Talk:Transverse Mercator projection

message: Anybody can contribute an image of a world map in UTM? --Lev 19:44, 7 May 2004 (UTC)
thread_title: Question

message: Nanometers or nautical miles?  —Preceding unsigned comment added by 72.40.45.79 (talk) 09:18, 8 February 2009 (UTC)
thread_title:  nm 

message: I have prepared a major rewrite of the Transverse Mercator page. The current contents are imbedded within the introductory outline and the first two sections. A new feature is the discussion of the properties of the transverse projection by contrasting them with the normal Mercator. There are two new large sections discussing the derivation of the spherical transverse mercator and a presentation of the formulae for the ellipsoidal transverse mercator. I have called these appendices to head off the casual reader. However I do feel that the mathematics should be up on Wiki even if it is accessible to few readers. If this proposal meets approval (or disapproval) please leave your comments on this page. Please do not edit the proposed page (in my user space) until it is moved up to this page --- if it does! At that stage I would appreciate editing of typos, errors, improvements to the text etc. Checking the maths is more problematic; all I can say is that the formulae come from a pdf article on mercator projections which has been checked by others. The proposed article is here,  Peter Mercator (talk) 17:36, 3 April 2010 (UTC)
replies: text: I'm very happy with this rewrite. It is wonderfully detailed. I have not checked all the formulæ, but those I looked at were correct. I would note Ensager and Poder's series development, also. (Engsager, K. E., and K. Poder, 2007 Aug., “A highly accurate world wide algorithm for the transverse Mercator mapping (almost),” in Proc. XXIII Intl. Cartographic Conf. (ICC2007), Moscow, p. 2.1.2.) Strebe (talk) 20:38, 4 April 2010 (UTC)
replies: text: This article increasingly diverges from good Wikipedia practices in the amount and scope of material. It is way too long, and the disparity between the information needed by a casual reader and the minutiæ of series computation is too great. Any number of series developments have been published. They do not belong in this article. Each should be broken off into separate articles, as well as any others people wish to detail. The article needs to get back to the fundamentals of the transverse Mercator. Strebe (talk) 20:44, 13 September 2010 (UTC)
thread_title:  Major rewrite 

message: Let's say we have come to this article looking for formulas to convert between lat-lon and transverse mercator. We know lat-lon is plotted on a spheroid, and we've learned the WGS84 defining parameters: equatorial radius 6378137 meters, reciprocal of the flattening 298.257223563 (hereinafter referred to as r). Getting started with the article we find
::In addition to the parameters a and e the series employ: 
::
\begin{align}
   b&=a(1-e^2)^{1/2},\qquad\qquad  n=\frac{a-b}{a+b}.
\end{align}
Looking thru the rest of the formulas we see we're going to need e^2 and n... but the author figures we shouldn't need to be told that e^2 equals (2r - 1)/r^2, so we have to go someplace else to learn that e^2 is 0.00669437999012 for the WGS84. Okay, now we need to calculate b; the author figures we shouldn't need to be told that b equals (r - 1)/r times a, so we plug e^2 into the formula he has given us and find that b is 6356752.31425 meters, allowing us to find that
:n \quad = \quad \frac {6378137 - 6356752.31425}{6378137 + 6356752.31425}
Think we might be a bit piqued when we someday learn that n is just 1/(2r - 1)?
Peter Mercator says the use of r is superfluous-- and it's true, it's only useful if you're aiming to give the reader the info he needs as simply and directly as possible. Tim Zukas (talk) 19:53, 16 September 2010 (UTC)
thread_title:  Ellipsoid formulas: imagine you're the reader 

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thread_title:  External links modified (January 2018)