ECW Pyramid

[José Ramón López]

Thxs for all.

I will do the last reply of Piero Cavalieri.

Thxs again.

On Dec 14, 2007 11:28 AM, Piero Cavalieri <Piero.Cavalieri at heidi.it> wrote:

>  You could use gdal_translate (http://www.gdal.org/gdal_translate.html) to
> decrease rasters resolution, and then gdal_merge (
> http://www.gdal.org/gdal_merge.html) to create mosaic. The process could
> be scripted (but in Windows some gdal commands does not accept jolly
> characters).
>
> You iterate this process some times and at every step you create a tile
> index. Every tile index is a Mapserver LAYER, and all of the layers belong
> to the same GROUP, which will be used as "the" layer in the query to
> Mapserver.
>
>
>
> Does this help u ?
>
>  Piero
>
>
>  ------------------------------
>
> *From:* UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] *On
> Behalf Of *Rahkonen Jukka
> *Sent:* giovedì 13 dicembre 2007 9.53
> *To:* MAPSERVER-USERS at LISTS.UMN.EDU
> *Subject:* Re: [UMN_MAPSERVER-USERS] ECW Pyramid
>
>
>
> Hi,
>
>
>
> To my understandment and experience it is unnecessary to have anything
> like ECW pyramids if you mean by that the same thing as with Geotiffs, for
> example.  That is, downsampled versions of individual image files.
> ECW has a wavelet based internal system for getting the same effect and it
> works fine.
>
>
>
> Another thing is that if you are looking your site through tile index and
> you have zoomed out very far then pyramid layers (or overviews or whatever
> they are called) do not help very much.  In this case MapServer has to open
> a bunch of physical files from the file system, perhaps tens of image files,
> and that will ineviatably slow down the response time.  What will help in
> this case is a separate, radically downsampled image that covers large area
> of your imagery.  For example, we have often sites which are 50 km by 50 km
> in size and they hold 100 aerial images with 0.5 metre pixel size.
> Zooming to whole site through tile index means that all the 100 files must
> be opened and it is for sure always slow with any file format and whether we
> have fine internal pyramids or not.  Pyramids do help a bit but the key to
> the speed is to avoin opening so many files from disk.  What we use to do is
> to create a quick look image with something like 10 metre pixel size and use
> that until the user has zoomed in so close that the resolution is not good
> enough.  At that moment only 1-4 original images must be opened through
> tileindex and that goes fast.
>
>
>
> A simple way to create a quick look image is to define Geotiff
> outputformat in the mapfile and ask MapServer to send the image with whole
> site extents with some reasonable width and height.
>
>
>
> -Jukka Rahkonen-
>
>
>  ------------------------------
>
> *Lähettäjä:* UMN MapServer Users List [mailto:
> MAPSERVER-USERS at LISTS.UMN.EDU] *Puolesta *José Ramón López
> *Lähetetty:* 12. joulukuuta 2007 14:09
> *Vastaanottaja:* MAPSERVER-USERS at LISTS.UMN.EDU
> *Aihe:* [UMN_MAPSERVER-USERS] ECW Pyramid
>
> Hi List.
>
> I have populated a raster layer using a Tileindex made from ECW Files.
> This layer is visible 1:1000 scale with MAXSCALE parameter.
> As is not possible to create ECW pyramids. Whe have got another raster
> layer resampling these ECW files.
> We would like to populate a single raster layer that uses one tile index
> created from the resampled ECW, visible at 1:10000 scale (and smaller), and
> another tileindex from the original ECW files visible at bigger scales.
> Is it possible? If not, please tell me how could I do something similar.
>
> Tnaks.
>
>
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