From: address@is.invalid   
      
   Paul,   
      
   > The CoPilot formula is capped to the valid range.   
   >   
   >        /* Clamp latitude to Mercator limits (approximately plus or minus   
   > 85.05113 degrees) */   
   >        if (lat > 85.05113) lat = 85.05113;   
   >        if (lat < -85.05113) lat = -85.05113;   
      
   I tested 85 degrees latitude too, which gave a 0.500 result - cutting Russia   
   vertically in two.  Hey, when 89 degrees latitude returns something as low   
   as 0.766 , what did you expect ?   
      
   > I would have liked to pump data points for an outline map into   
   > this little project, to see if the projection makes sense, but I   
   > could not find any hint of available data decks online.   
      
   I found a number of Mercator maps (one of them I provided in my initial   
   message), and even a few in .SVG form.  Like this one :   
      
   https://mathworld.wolfram.com/MercatorProjection.html   
      
   (Its also the one where I got my initial formule from)   
      
   I also got a few reference lat/lon coordinates :   
      
   https://time-ok.com/coordinates/north-america   
   https://time-ok.com/coordinates/europe   
      
   > There are likely to be more than one Mercator projection.   
      
   Not too many, if I may believe Wikipedia :   
      
   https://en.wikipedia.org/wiki/List_of_map_projections   
      
   By the way, I do not see any difference beween the "Mercator = Wright" and   
   "Web Mercator" images.   
      
   > That's why I wanted to plot off a unit square with the world in it,   
   > just to check that the presentation looks like the map in Wiki.   
      
   Thats what I started with (the above links are the result of it). :-)   
      
   > This is what CoPilot offered as cites.   
      
   My browser "doesn't do" JS, so no joy on the first two links   
      
   > https://ourworldindata.org/grapher/continents-according-to-our-world-in-data   
      
   That one looks to be an Equirectangular projection, and is easy to plot on -   
   lineair in both directions.   
      
   Alas.  Although I can access the last webpage, I get 403 status when I try   
   to access the webp images.   
      
   > Looks about as pleasant as yard work.   
      
   :-)  Some people happen to like yard work.  But yes, it is tedious.  Extra   
   fun was gotten when reading that log() != log() .   
      
   Regards,   
   Rudy Wieser   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)