[Gdal-dev] Tiff on the CD

[Richard Greenwood]

At 09:27 AM 10/25/2003 +0800, you wrote:

>Hi!
>If many situations, the original tiff file can't be modified(on CD or DVD 
>or file marked with ReadOnly property), but the user still like it be 
>zoomed out smoothly. In CD, the read speed is much slowly than harddisk, 
>so if I take RasterIO to build a overview of whole image on screen will 
>take a long time. If the user wanna access the data more than once, it 
>will be better we keep a overview cache on harddisk. Next time the user 
>insert the CD or DVD (maybe access on a automatic CD library), the 
>software will recognize the file(by CD volume number or something else), 
>and associate the overview cache in the harddisk with it.
>If we can't sperate overviews from details in Geotiff format. If it 
>possible to create new feature in vrt that tell where to find the 
>overviews and where to find the detail.

Are you using mapserver to serve the data? If you are then you could use 
MINSCALE and MAXSCALE to switch between layers that are on the CD and 
layers on your hard disk which have overviews. But you would really be 
better off with all your images on a hard disk.

Rich

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com