[OpenLayers-Users] Recommended projection for

[Petra Staub]

Hi all

I have a big image, represented by many tiles in different zoom levels. I have them
stored locally in following (OSGEO recommended) structure:

../<zoom_level>/<x-coordinate>/<y-coordinate>.jpg

I managed to somehow to display them in OpenLayers, however, I still have little
bit a mess with resolutions and zoom levels. ;-)

Question: 
1) Is there a recommended projection for plain, tiled images (if ignoring DPI, there is no
actual unit, simple pixels)? I see people using mercator projections (EPSG:410001,
EPSG:27700, EPSG:3005, EPSG: 900913,...) but I can't tell which one is 
appropriate for me. Does this matter at all for my simple case?

2) My highest zoomlevel/resolution contains one tile which represents the complete, full 
image and currently is located at .../<highest-zoom-level>/0/0.jpg.
I realized that some projections have for the highest resolution two tiles (e.g. EPSG:4326),
other one, as I have (OSGEO:41001. With my limited knowledge, this seems to me
a bit confusing. Especially in respect the the overview-map feature of OpenLayers,
do I have to consider this for the selection of the projection or is this all simply a question
of configuration of OpenLayers?

3) I think, the origin for a layer can be set. As my coordinates may also be negative 
(the origin of the displayed image is in the middle of the picture), can this simply be
configured or do I have to shift the coordinates with some TileProvider so (0,0)
comes to the left bottom corner of the OpenLayers coordinate system.

I hope I don't annoy people with my (may be stupid) beginner questions,
but I am very grateful for any tips, comments or examples!

Petra



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