[mapguide-users] Generating tiles for google maps
azpublic
azpublic at bluewin.ch
Fri Dec 21 17:06:21 EST 2007
OK Here's a little follow up of what I've been experimenting given the
information I have.
I took a google zoom of 11 / Virtual earth zoom of 6 which according to the
MSDN Article corresponds to a scale of 1 : 9244667.36
I created my base layers in Studio with a unique zoom level of 9244667.36
and tried to generate the tiles using FMTiling engine and specifying the
given scale.
Here is a google Tile of Switzerland
http://mt3.google.com/mt?n=404&v=w2.66&x=33&y=22&zoom=11&s=G
and here is a png of the tile I generated (see attachment 0_0.png I hope
the list accepts attachments ... ).
If you try and paste the two in some image editor and overlay them you will
see that the scale seems to match correctly.
The only thing is that the tile I generated is not centered correctly.
I don't know if this has to do with the projection problem you are talking
about in some other posts.
What do you think I could try to calibrate the tiles correctly ?
Thanks again for your support.
Cheers
Alex !
-----Original Message-----
From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of azpublic
Sent: jeudi, 20. décembre 2007 18:06
To: 'MapGuide Users Mail List'
Subject: RE: [mapguide-users] Generating tiles for google maps
I found out this article talking about MS virtual earth / live maps
http://msdn2.microsoft.com/en-us/library/bb259689.aspx
They show us how we can calculate the scale ...
Now my next question:
Is the scale displayed in mapguide studio calculated at the equator when in
a Mercator projection?
If yes I think we could generate the tiles pretty easily using the
FMTilingEngine and the appropriate projection
-----Original Message-----
From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of azpublic
Sent: jeudi, 20. décembre 2007 17:05
To: 'MapGuide Users Mail List'
Subject: RE: [mapguide-users] Generating tiles for google maps
Thanks for your help.
I think the problem if we do it this way is that the zoom levels won't match
precisely.
Google and Microsoft use QuadTiles for their maps.
Meaning that each tile at a specific zoom level is divided in 4 tiles at the
next zoom level.
I thought that with this information we could figure out what were the
different MapGuide zoom levels to define in studio and then reuse them in
the automated tiling engine ...
For example :
If at goolge zoom level 17 the world fits perfectly in a 256 x 256 pixels
square we could calculate the corresponding mapguide scale ??? am I wrong ?
http://mt0.google.com/mt?n=404&v=w2.66&x=0&y=0&zoom=17&s=
Then do the same at zoom level 16 where the world is (2 x 256) x (2x256)
pixels and so on.
We could then use these scales in the automated Tiling Engine for a specific
Map of which the boundaries would exactly correspd to a given Google maps
tile at a higher zoom level.
What do you think ?
-----Original Message-----
From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of George McLean
Sent: mercredi, 19. décembre 2007 20:57
To: MapGuide Users Mail List
Subject: Re: [mapguide-users] Generating tiles for google maps
I was thinking you could create a layer that was your bounding box and
then add your map to a weblayout. Open the web layout in a browser and
as you zoom in to the corners of your bounding box the tiles will get
created under the TileCache directory (at least in windows). There may
be a better way to do this but that is how I have created tiles for
regions within a larger map.
Thanks for the Chris Savage link. I read it a few weeks ago but now that
I have been working on this it was helpful to re-read.
George
azpublic wrote:
> Yes it is a mercator projection and it’s the one I've been using for my
map.
>
>
> Here is a good post about the subject.
>
> http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed
>
> What do you mean by "I would create the box and
> then zoom to the corners" ?
>
>
>
> -----Original Message-----
> From: mapguide-users-bounces at lists.osgeo.org
> [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of George McLean
> Sent: mercredi, 19. décembre 2007 17:26
> To: MapGuide Users Mail List
> Subject: Re: [mapguide-users] Generating tiles for google maps
>
> I have been trying to get this working as well. My approach has been to
> use data between 85 degrees north and 85 degrees south in a Mercator
> projection since this is what I believe Google maps uses. I am still not
> sure if this is the right approach as I am still working on it.
>
> To get the tiles within your bounding box, I would create the box and
> then zoom to the corners. The tiles for that region will be created and
> this will help you figure out the rows and columns for each corner at
> each zoom level. Once you know the zoom levels and row/column boundaries
> you can specify these parameters in the call to the tiling engine.
>
> George McLean
>
> azpublic wrote:
>
>> Hi,
>>
>>
>>
>> I’m looking for a way to generate custom tiles for google maps or Ms
>> Live maps / Virtual earth using Mapguide OS.
>>
>>
>>
>> I’ve created my map using studio and I’m now thinking about using the
>> Automated tiling engine from WSD to generate the tiles.
>>
>>
>>
>> My main problem is about which scale to use to have my custom tiles
>> match with google maps tiles. What are the mapguide scales I need to
>> use for specific google maps zoom levels?
>>
>>
>>
>> Moreover I want to generate tiles only for a specific lat/lon bounding
>> box. Is this possible using the Tiling engine?
>>
>>
>>
>> Any help appreciated !
>>
>>
>>
>>
>>
>>
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