I've noticed that lots of map viewer (especially those nautical chart viewer) will shrink a mercator projected chart while panning towards poles.

Is this some compensation for mercator distortion?

Is this a dedicated projection?

How to implement that?

  • you shouldn't crosspost in all possible sites/mailing list's... it is not a correct approach: 1 & 2
    – Gago-Silva
    Commented Feb 4, 2013 at 9:41
  • 2
    Formulas for the scale of a Mercator projection are given in the answer at gis.stackexchange.com/a/40659. Concerning your last question, what platform do you intend to use for the implementation?
    – whuber
    Commented Feb 4, 2013 at 14:23
  • 1
    Here is a little puzzle that will illustrate what google mercator does. Mercator puzzle
    – Brad Nesom
    Commented Feb 4, 2013 at 16:19
  • I'm thinking that the shrink is to make the scale always the same along latitude, so , say (px, py) is normally projected coordinate, to get it shrinked, use (x, y) = (pxcos(lat), pycos(lat))
    – feverzsj
    Commented Feb 5, 2013 at 0:44
  • 1
    If the Mercator implementation supports a standard parallel, they may be changing it to match the screen's central latitude. That will "shrink" a Mercator-based map.
    – mkennedy
    Commented Feb 7, 2013 at 21:08


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