[OpenLayers-Users] offsetting TMS layers...

[Lance Dyas]

Creating large tile sets is sometimes a technical burden.. (particularly 
if you are not able to use tilecache)
 what I am interested  in.. is merging tile sets. by using different 
layers Is it possible to define a layer as
 being offset from the basic map definition The map goes from 0 to 30000 
wide and 0 to 30000 high
but has 4 tilesets.. each generated as  15000 x 15000 ...can I offset 
these layers
ie.
[0 to 15000] [0 to 15000 ] 
[0 to 15000] [15000 to 30000] 
[15000 to 30000] [0 to 15000 ]
[15000 to 3000] [1500 to 30000]

Will I need ot use pngs (ie something with transparency or could I get 
away with jpegs
for the main images and pngs for areas outside the area of data..  what 
about the border
cases?