Folks,
I'm sorry for speaking up on this without having read the other replies. Forgive me for repeating information. Edi.Karadumi wrote:
as you may know, i have very slow performance when i zoom out and im stucked here. As i have read i should make a copy of the tiles with reduced resolution. Merge the tiles together and use min/max scale to show different layers in different scales. the min/max scales i zoom in/out are 100/1200000. Now my questions are - How can i calculate the scale where i should create another layer of the tiles, or i shoud see it with some tests?
I find the MapServer scale values very confusing myself. If I want to compute the scale for particular request (for instance to establish breakpoints for MINSCALE/MAXSCALE), I do a request at the target resolution with shp2img and debug output on and examine the debug output for the scale reported.
- how much should be the resolution of the new layer?
You basically want to move to a new mosaiced overview layer at the point where a map request is likely to request several tiles at once. If we, roughly, assume a map request is on the order of 500x500 then at 32 times reduction in resolution would give a request over an area of 16000 x 16000 which is certain to touch several of your 6000 x 6000 base files. So, I'd aim to have this merged mosaic at approximately 1/32nd of the resolution of the original imagery. 1200GB of full res imagery reduced to 1/32nd resolution is only about 1GB so it is a very managable size for an overview layer.
- is there any tools or program to merge the tiles? merging 6000 tiles with the gdalwarp by writing the command by myself is frustrating
gdalwarp can take multiple input files in one run, but there are some issues with how gdalwarp is implemented that make it not scale well to many input files without great care. Since the input files are quite a modest size I would suggest using gdal_merge.py to mosaic them at a reduced resolution. If your original imagery were 5m pixels something like: gdal_merge.py -o overview_mosaic.tif -ps 160 160 */*.tif might do the trick.
- how many tiles should i merge together to create the new layer? (how many tiles should have the new layer) i know that in each zoomscale its better to appear only one tile but i dont know how to calculate it - the tiles that i should merge are the originals or those with internal tiling and overviews?
If you use gdal_merge.py, it is best to use input files that have overviews already built. This will ensure that the mosaic built uses the same downsampling technique (ie. averaging) that you used to build the overviews. It will also make the mosaicing much faster. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users