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GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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Andriy T. Yanko  
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 More options Nov 16 2007, 5:29 am
From: "Andriy T. Yanko" <andriy.ya...@gmail.com>
Date: Fri, 16 Nov 2007 02:29:30 -0800 (PST)
Local: Fri, Nov 16 2007 5:29 am
Subject: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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Hi all.

I need implement GMercatorProjection's   fromPixelToLatLng and
(fromLatLngToPixel ) functions in other language.

With longitude its tricky.
But I cant properly find latitude for different  map zoom levels
(0-17).

Could you please explain how to calculate latitude?

Thx.


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Eirik  
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 More options Nov 18 2007, 11:47 am
From: Eirik <eirir...@gmail.com>
Date: Sun, 18 Nov 2007 08:47:09 -0800 (PST)
Local: Sun, Nov 18 2007 11:47 am
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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This is from the source, hope it helps:

Uc.prototype.fromLatLngToPixel = function (a, b) {
        var c = this, d = c.Pm[b], e = G(d.x + a.lng() * c.Rm[b]), f =
Ka(Math.sin(Ee(a.lat())), -0.9999, 0.9999), g = G(d.y + 0.5 *
Math.log((1 + f) / (1 - f)) * -c.Sm[b]);
        return new o(e, g);

};

Uc.prototype.fromPixelToLatLng = function (a, b, c) {
        var d = this, e = d.Pm[b], f = (a.x - e.x) / d.Rm[b], g = (a.y -
e.y) / -d.Sm[b], h = Kb(2 * Math.atan(Math.exp(g)) - $ / 2);
        return new F(h, f, c);


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bratliff  
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(2 users)  More options Nov 18 2007, 12:44 pm
From: bratliff <bratl...@umich.edu>
Date: Sun, 18 Nov 2007 09:44:07 -0800 (PST)
Local: Sun, Nov 18 2007 12:44 pm
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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On Nov 16, 10:29 am, "Andriy T. Yanko" <andriy.ya...@gmail.com> wrote:

> Hi all.

> I need implement GMercatorProjection's   fromPixelToLatLng and
> (fromLatLngToPixel ) functions in other language.

> With longitude its tricky.
> But I cant properly find latitude for different  map zoom levels
> (0-17).

> Could you please explain how to calculate latitude?

> Thx.

var offset=16777216;

var radius=offset / Math.PI;

LToX=function(z,w,x,y)
{
        return (offset+radius*x*Math.PI/180)>>z;

}

LToY=function(z,w,x,y)
{
        return (offset-radius*Math.log((1+Math.sin(y*Math.PI/180))/(1-
Math.sin(y*Math.PI/180)))/2)>>z;

}

XToL=function(z,w,x,y)
{
        return (((x<<z)-offset)/radius)*180/Math.PI;

}

YToL=function(z,w,x,y)
{
        return (Math.PI/2-2*Math.atan(Math.exp(((y<<z)-offset)/radius)))*180/
Math.PI;

}

The "z" parameter is the zoom level.  Ignore the "w" parameter.  It is
the UTM zone.  It is null for Mercator.

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Andriy T. Yanko  
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 More options Nov 18 2007, 3:47 pm
From: "Andriy T. Yanko" <andriy.ya...@gmail.com>
Date: Sun, 18 Nov 2007 12:47:12 -0800 (PST)
Local: Sun, Nov 18 2007 3:47 pm
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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Interesting, but what does mean operator '<<' in your sources? (e.g
y<<z ).

On Nov 18, 7:44 pm, bratliff <bratl...@umich.edu> wrote:


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bratliff  
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 More options Nov 18 2007, 4:01 pm
From: bratliff <bratl...@umich.edu>
Date: Sun, 18 Nov 2007 13:01:06 -0800 (PST)
Local: Sun, Nov 18 2007 4:01 pm
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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On Nov 18, 8:47 pm, "Andriy T. Yanko" <andriy.ya...@gmail.com> wrote:

> Interesting, but what does mean operator '<<' in your sources? (e.g
> y<<z ).

<< is the shift left operator

>> is the shift right operator

Equivalent to multiplying / dividing by a power of two.  Both
automatically convert from floating point to fixed point.

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Barry Hunter  
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 More options Nov 18 2007, 5:18 pm
From: "Barry Hunter" <barrybhun...@googlemail.com>
Date: Sun, 18 Nov 2007 22:18:27 +0000
Local: Sun, Nov 18 2007 5:18 pm
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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http://www.javascripter.net/faq/arithmet.htm

On Nov 18, 2007 8:47 PM, Andriy T. Yanko <andriy.ya...@gmail.com> wrote:

--
Barry

- www.nearby.org.uk - www.geograph.org.uk -


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Valery  
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 More options Nov 19 2007, 4:15 am
From: Valery <valery.bogda...@gmail.com>
Date: Mon, 19 Nov 2007 01:15:56 -0800 (PST)
Local: Mon, Nov 19 2007 4:15 am
Subject: Re: GMercatorProjection: fromLatLngToPixel and fromPixelToLatLng implementation.
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On Nov 16, 12:29 pm, "Andriy T. Yanko" <andriy.ya...@gmail.com> wrote:

> But I cant properly find latitude for different  map zoom levels
> (0-17).

Actually there is twenty zoom levels in Google Maps:
- from 0 to 17 for "Map" map type;
- from 0 to 19 for "Satellite" and "Hybrid" map types

WBR,
Valery.


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