From 5b72015b0aaca836ee0e8bf1f2da193574fe8ab1 Mon Sep 17 00:00:00 2001 From: Charles Karney Date: Thu, 22 Oct 2020 13:53:45 -0400 Subject: merc.rst: revert to ln instead of log. Also define merc (resp. tmerc) as the conformal projection in which the equator (resp. a chosen meridan} projects to a straight line at constant scale. --- docs/source/operations/projections/merc.rst | 13 +++++++------ docs/source/operations/projections/tmerc.rst | 2 ++ 2 files changed, 9 insertions(+), 6 deletions(-) (limited to 'docs/source') diff --git a/docs/source/operations/projections/merc.rst b/docs/source/operations/projections/merc.rst index 62aa5bc9..c474009f 100644 --- a/docs/source/operations/projections/merc.rst +++ b/docs/source/operations/projections/merc.rst @@ -6,9 +6,10 @@ Mercator The Mercator projection is a cylindrical map projection that origins from the 15th century. It is widely recognized as the first regularly used map projection. -The projection has the property that a rhumb line, a course of constant -heading, projects to a straight line. This makes it suitable for -navigational purposes. +It is a conformal projection in which the equator projects to a straight +line at constant scale. The projection has the property that a rhumb +line, a course of constant heading, projects to a straight line. This +makes it suitable for navigational purposes. +---------------------+----------------------------------------------------------+ @@ -99,7 +100,7 @@ Forward projection .. math:: - \psi &= \log \tan \biggl(\frac{\pi}{4} + \frac{\phi}{2} \biggr)\\ + \psi &= \ln \tan \biggl(\frac{\pi}{4} + \frac{\phi}{2} \biggr)\\ &= \sinh^{-1}\tan\phi The quantity :math:`\psi` is the isometric latitude. @@ -143,9 +144,9 @@ Forward projection .. math:: - \psi &= \log\tan\biggl(\frac\pi4 + \frac{\phi}2\biggr) + \psi &= \ln\tan\biggl(\frac\pi4 + \frac{\phi}2\biggr) -\frac12 e - \log \biggl(\frac{1 + e \sin\phi}{1 - e \sin\phi}\biggr)\\ + \ln \biggl(\frac{1 + e \sin\phi}{1 - e \sin\phi}\biggr)\\ &= \sinh^{-1}\tan\phi - e \tanh^{-1}(e \sin\phi) diff --git a/docs/source/operations/projections/tmerc.rst b/docs/source/operations/projections/tmerc.rst index 3b2a0190..7fed3846 100644 --- a/docs/source/operations/projections/tmerc.rst +++ b/docs/source/operations/projections/tmerc.rst @@ -5,6 +5,8 @@ Transverse Mercator ******************************************************************************** The transverse Mercator projection in its various forms is the most widely used projected coordinate system for world topographical and offshore mapping. +It is a conformal projection in which a chosen meridian projects to a +straight line at constant scale. +---------------------+----------------------------------------------------------+ | **Classification** | Transverse and oblique cylindrical | -- cgit v1.2.3