[Tilecache] Help with resolution setup..

[Mark Deneen]

Christopher Schmidt wrote:
> On Tue, Jan 08, 2008 at 11:59:23AM -0500, Mark Deneen wrote:
>   
>> I am trying to figure out what units "resolution" is in.  I am using the 
>> following config:
>>
>> [basic]
>> type=WMS
>> url=http://this.is.internal.only.but.it.is.a.geoserver.wms.handler/
>> layers=basic
>> extension=png
>> metaTile=true
>> size=256,256
>> srs=EPSG:4326
>> resolutions=0.1
>> bbox=-180.0,-90.0,180.0,90.0
>>
>> Let me preface this by saying that I am fairly new at GIS and 
>> cartography. With that being said....
>>
>> I would like to think that 0.1 means 36 degrees / 360 (from my bbox) = 
>> 0.1.  This should make the world (in EPSG:4326) 50 tiles, 10 east/west 
>> columns of  5 north/south rows. Obviously, since I am writing this 
>> email, this isn't working for me.  I am using world wind requests and at 
>> resolution 0.1, I end up with 6 tiles N/S and 13 E/W.  I really want to 
>> understand what resolution is, and how I can calculate it.  Currently, I 
>> want to dice the map up into 36 degree squares for testing.
>>
>> Can someone shed some light on what resolution is, or where I can read 
>> more about it?
>>     
>
> Resolution is units per *pixel*, rather than per tile: you probably want
> something like .140625 (36 degrees / 256) to get 36 degree squares. 
>
> Also, TileCache can spit out WorldWind XML metadata which you can load
> directly -- let me know if you can't figure out how to make that happen. 
>
> Regards,
>   
Christopher,

Thanks.  This was very helpful.  As for the XML metadata, I am not 
exactly using WorldWind.  I just liked the simplicity of the tile system 
and wanted to use tilecache because it does a nice job with 
meta-tiling.  Eventually the tilecache generated tiles will end up on a 
flash card after some post-processing to a custom NTSC safe palette, and 
displayed on a television set.

Thanks again,
Mark