[OSM-newbies] Converting lat/lon to pixel within a tile

[Vishwa]

Hi,

Thanks for the help. It works now.

- Vishwa

On Fri, May 2, 2008 at 7:08 PM, root <john at mckerrell.net> wrote:

> Hi
>
> Sorry I probably wasn't very clear in my previous email as I rushed it a
> bit, it was more intended to give you an idea how to work it out. I
> haven't loaded the tile in photoshop or anything but looking at your
> calculations and comparing them to a map tile, they do appear to have
> worked. The point on the tile that is at 142,11 pixels (from the top
> left) appears to be the point that you want to center on. How you center
> it will depend partly on how you're displaying, but perhaps moving the
> tile or the canvas as follows will do it:
>
> (256/2)-142=-14 pixels to the right (so 14 pixels to the left)
> (256/2)-11=117 pixels down
>
> As I say, depends how you're displaying things but I think that playing
> with these numbers should do the job.
>
> John
>
> On Fri, May 02, 2008 at 05:59:20PM +0530, Vishwa wrote:
> > Sorry, it still not working.
> > Here are my values:
> >
> > lon =  -0.127144
> > lat  = 51.506324999991364
> > zoom = 12
> >
> > From which i calculate:
> > xtile = 2046
> > ytile = 1362
> >
> > Also, as you suggested i tried to take the decimal part and determine how
> > much the tiles have to be moved:
> > X
> > 2046.5533838222223
> > 0.5533838222223 X 256 = 141.6 = 142 pixels
> >
> > Y
> > 1362.0441915021011
> > 0.044191502101057267 * 256 = 11.31 = 11pixels
> >
> > Is this calculation is according to what you have suggested?
> > The end result is not centering the map.
> >
> > Regards,
> > Vishwa
> >
> > On Wed, Apr 30, 2008 at 4:12 PM, root <john at mckerrell.net> wrote:
> >
> > > If you convert the lat/lon to a floating point tile coordinate you can
> > > then use the decimal part to tell you how much you need to shift the
> > > tiles. Multiply it by 256 and that'll tell you how far. That help?
> > >
> > > On Wed, Apr 30, 2008 at 03:55:55PM +0530, Vishwa wrote:
> > > > i am doing this using C#.Net to create a image out of tiles, and i
> have
> > > to
> > > > center the image to the given image
> > > >
> > > > i know the zoom level, and the center coordianates, and the size of
> the
> > > 3x3
> > > > grid. how to center align the map when the center can be anywhere
> within
> > > the
> > > > 256x256 center tile?
> > > >
> > > > thanks
> > > > vishwa
> > > >
> > > >
> > > > > On Wed, Apr 30, 2008 at 1:15 PM, Iv??n S??nchez Ortega <
> > > > > ivan at sanchezortega.es> wrote:
> > > > >
> > > > > > El Mi??rcoles, 30 de Abril de 2008, Vishwa escribi??:
> > > > > > > In other words, how to know the pixel (x,y) *within the center
> > > tile*
> > > > > > for a
> > > > > > > given lon,lat value.
> > > > > >
> > > > > > If you're using javascript, please keep in mind that there are
> > > > > > OpenLayers
> > > > > > functions for this.
> > > > > >
> > > > > > --
> > > > > > ----------------------------------
> > > > > > Iv??n S??nchez Ortega <ivan at sanchezortega.es>
> > > > > >
> > > > > > "Anything that is too stupid to be spoken is sung."
> > > > > >  - Voltaire (1694-1778) [poor guy, never knew about rap]
> > > > > >
> > > > >
> > > > >
> > >
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