Mercator projection that shrinks toward pole

[feverzsj]

hi, list
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 under qgis?

[b.j.kobben]

Well, if it's shrinking towards the poles, it basically is not a Mercator
projection (at least not the traditional normal Mercator where the
cylinder is wrapped around the Equator)...

Which "nautical chart viewer" did you see this in...?

--
Barend Köbben
Senior Lecturer, ITC - University of Twente,
Faculty of Geo-Information Science and Earth Observation
PO Box 217, 7500AE Enschede (The Netherlands)
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On 04-02-13 06:26, "feverzsj" <[hidden email]> wrote:

>hi, list
>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 under qgis?
>
>
>
>
>--
>View this message in context:
>http://osgeo-org.1560.n6.nabble.com/Mercator-projection-that-shrinks-towar
>d-pole-tp5031876.html
>Sent from the Quantum GIS - User mailing list archive at Nabble.com.
>_______________________________________________
>Qgis-user mailing list
>[hidden email]
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[feverzsj]

hi, b.j.kobben
>> Well, if it's shrinking towards the poles, it basically is not a Mercator projection (at least not the traditional normal Mercator where the cylinder is wrapped around the Equator)...

It shrinks in a way that the whole canvas is scaled down. Considering the Mercator is always recommended for nautical application, it should be Mercator projection with some post process.

>> Which "nautical chart viewer" did you see this in...?

For example, Transas's ECDIS demo, DEMO_ECDIS_2519.iso : http://www.transas.com/support/ecdis_demo/

[b.j.kobben]

I am sorry, but that makes no sense. If you scale down the top or bottom
part of a Mercator projected map, it looses the one thing it's useful for
in nautical apps, namely that a compass course is depicted as a straight
line in any direction...


Barend

On 04-02-13 09:49, "feverzsj" <[hidden email]> wrote:

>hi, b.j.kobben
>>> Well, if it's shrinking towards the poles, it basically is not a
>>>Mercator
>>> projection (at least not the traditional normal Mercator where the
>>> cylinder is wrapped around the Equator)...
>
>It shrinks in a way that the whole canvas is scaled down. Considering the
>Mercator is always recommended for nautical application, it should be
>Mercator projection with some post process.
>
>>> Which "nautical chart viewer" did you see this in...?
>
>For example, Transas's ECDIS demo, DEMO_ECDIS_2519.iso :
>http://www.transas.com/support/ecdis_demo/
>
>
>
>--
>View this message in context:
>http://osgeo-org.1560.n6.nabble.com/Mercator-projection-that-shrinks-towar
>d-pole-tp5031876p5031902.html
>Sent from the Quantum GIS - User mailing list archive at Nabble.com.
>_______________________________________________
>Qgis-user mailing list
>[hidden email]
>http://lists.osgeo.org/mailman/listinfo/qgis-user

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