XPost: alt.windows7.general, alt.comp.os.windows-10   
   From: address@is.invalid   
      
   John,   
      
   > There are three stages to this   
   ...   
   > 1. The mathematical conversion from latitude (and longitude) to the   
   > position on the plane map *relative to its centre*   
      
   Nope.  There is no rule that that center must be taken as the origin.   Take   
   the formule Paul provided for instance.  It returns a result in the range of   
   0 to 1 .   
      
   > 2. The _scaling_ required, depending on the size of the map image.   
   > Which again will depend on the size of the image (and may be different   
   > for X and Y).   
      
   Worse : Mercator maps go from +85 to -85 latitude.  That must be part of the   
   formule (I've found several maps where the south-pole is cut off, and a bit   
   of the north too. iow, useless without further information).   
      
   But again no.   The result of the formule *is* the scaling (in your and my   
   usage ranging from +1 to -1, in Pauls formule case, from 0 to +1).  You just   
   apply it on whatever size Mercator-style map you have handy.   
      
   > I think _most_ of those contributing to this discussion know that,   
   > but have not been making it very clear which bits of their formula(e)   
   > do what.   
      
   I do not need to know what all the parts of a car do, as long as I can drive   
   it.  The same goes for these two formules.   Latitude goes in, something I   
   can apply comes out.   
      
      
   Though the whole problem isn't that nobody understood what you said there,   
   but that nobody was willing to compare the (intermediate) results I posted   
   with what they got themselves, allowing me to locate where I made my   
   mistake(s?).   
      
   Not when I asked for it in my first post, and not when I rather explicitily   
   asked for it a few days back. :-(   
      
   Regards,   
   Rudy Wieser   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)