anchor.diff:  :toclevels: 3
   :source-highlighter: coderay
   :icons: font
  +:stem: latexmath
   
   == Introduction
   
  
positive.code: _phpgeo_ is best be installed using Composer. Please visit the
  https://getcomposer.org/[Composer website] website for more information.
  
  To install _phpgeo,_ simply _require_ it using Composer:
  
      php composer.phar require mjaschen/phpgeo
  
  
negative.code: 
  === Ellipsoid
  
  An ellipsoid is a mathematically defined approximation of the earth's surface.
  
  An ellipsoid is defined by two parameters:
  
  * the semi-major axis _a_ (equatorial radius)
  * the semi-minor axis _b_ (polar radius)
  
  _a_ and _b_ together define the flattening of the ellipsoid _f_:
  
  latexmath:[f = \frac{a-b}{a}]
  
  NOTE: _phpgeo's_ ellipsoids are defined by _a_ and _1/f_ instead of _a_
  and _b_. That's not a problem because each third value can be
  calculated from the other two.
  
  _phpgeo_ supports arbitrary ellipsoids. _WGS-84_ is used as default when
  no other ellipsoid is given. For day-to-day calculations it's not needed
  to care about ellipsoids in the most cases.
  
  It's possible to create an instance of the Ellipsoid class either by
  specifing a name or by providing the three parameters _name,_ _a_, and _1/f_.
  
  [source,php]
  ----
  use Location\Ellipsoid;
  
  $ellipsoid = Ellipsoid::createDefault('WGS-84'); <1>
  
  printf(
      "%s: a=%f; b=%f; 1/f=%f\n",
      $ellipsoid->getName(),
      $ellipsoid->getA(),
      $ellipsoid->getB(),
      $ellipsoid->getF()
  );
  
  $ellipsoid = new Ellipsoid('GRS-80', 6378137, 298.257222); <2>
  
  printf(
      "%s: a=%f; b=%f; 1/f=%f\n",
      $ellipsoid->getName(),
      $ellipsoid->getA(),
      $ellipsoid->getB(),
      $ellipsoid->getF()
  );
  ----
  
  <1> Create ellipsoid instance from one of the default configurations
  <2> Create custom ellipsoid by providing name, _a_, and _1/f_
  
  The code above will produce the output below:
  
  ----
  WGS-84: a=6378137.000000; b=6356752.314245; 1/f=298.257224
  GRS-80: a=6378137.000000; b=6356752.314133; 1/f=298.257222
  ----
  
  == Calculations
  
  === Distance and Length
  