Using gdal2tiles with multiple images / ArcSDE layers
Chris
I would appreciate your advice on using gdal2tiles with multiple
images.
I have 2,100 TIFF images, with TIFF World Files, that with a blank
white pixel, have been mosaicked together into ArcSDE. These are
viewable at: http://geo.nls.uk/os6inch/ and through the WMS
http://geo.nls.uk:80/wmsconnector/com.esri.wms.Esrimap? The original
TIFF images together take up about 900 Gb
You have helpfully advised before that I could use the gdal_translate
command (with an XML description of the WMS following
http://www.gdal.org/frmt_wms.html), but the image quality would be
poorer than using original files with gdal2tiles. Would you advise me
still to try this gdal_translate option from the WMS - and if so, what
image format should I generate from the SDE layers, given file sizes?
I am not sure whether a better option would be to process the multiple
TIFF images through gdal2tiles, but only if a batch process were
possible...
Many thanks in advance (and Happy New Year to you too!)
Chris
klo...@gmail.com
> I would appreciate your advice on using gdal2tiles with multiple
> images.
>
> I have 2,100 TIFF images, with TIFF World Files, that with a blank
> white pixel, have been mosaicked together into ArcSDE. These are
> viewable at: http://geo.nls.uk/os6inch/ and through the WMS
> http://geo.nls.uk:80/wmsconnector/com.esri.wms.Esrimap? The original
> TIFF images together take up about 900 Gb
As soon as you have correct georeference (world files + epsg) for all
those images I recommend you to merge them into one virtual dataset
with huge dimensions using GDAL VRT driver (small XML textual file
telling where to place each file and what operation do on it).
A utility gdal_vrtmerge.py can help you in that case - I prepared a
patched version of it for gdal2tiles.py purposes.
Such merged virtual dataset can be tiled directly by gdal2tiles
utiltity - and this is how parallel version of gdal2tiles is usually
used. Selecting of the NODATA color (blank white pixel) should not be
problem in the preprocessing step.
The size of the tifs should not be a problem in this case.
I will send you details to your private email.
> You have helpfully advised before that I could use the gdal_translate
> command (with an XML description of the WMS following
> http://www.gdal.org/frmt_wms.html), but the image quality would be
> poorer than using original files with gdal2tiles. Would you advise me
> still to try this gdal_translate option from the WMS - and if so, what
> image format should I generate from the SDE layers, given file sizes?
> I am not sure whether a better option would be to process the multiple
> TIFF images through gdal2tiles, but only if a batch process were
> possible...
Yes, this is the second possible way. When you create a textual XML
file describing WMS source GDAL is able to read the raster data
directly over the Internet. In this case you can setup an XML file for
read EPSG:4326 (because ESRI does not support yet the Google's
Spherical Mercator) data from your WMS server and let GDAL2Tiles
directly reproject/warp it and tile it into Google Maps overlay tiles.
There should not be need to use gdal_translate but for initial testing
of the WMS textual file correctness. There is definitively no need to
create a temporary copy of the rasters from WMS on your disk, they
should be read directly trough WMS by gdal2tiles in such case.
However, this second described workflow is not yet tested, but I think
there should not be any problem with it.
The generation of tiles from WMS is usually done by TileCache.org or
GeoWebCache.org projects. Advantage of the usage GDAL2Tiles for this
kind of generation would be the possibility to reproject existing
reference system from WMS into Google Maps Mercator during the tile
generation on the client side.
It means there would not be need to support EPSG:900913 on the server side.
Further testing of this approach is on the MapTiler TODO list. It
would be also cool to have the WMS as source option in the MapTiler
GUI, but unfortunately I don't have enough time right now to work on
this and it does not have as big priority, unless I find a client who
will need that.
Best regards
Klokan
Fleet, Christopher
Many thanks, as always, for these helpful explanations. I'll try out the
virtual dataset option and let you know, but the WMS option is useful to
know of.
Best wishes,
Chris
Visit the National Library of Scotland online at www.nls.uk
CELEBRATING 500 YEARS OF SCOTTISH PRINTING 1508-2008
http://www.500yearsofprinting.org
***********************************************************************
Please consider the environment before printing this e-mail.
This communication is intended for the addressee(s) only. If you
are not the intended recipient, please notify the ICT Helpdesk on
+44 131 623 3700 or i...@nls.uk and delete this e-mail. The
statements and opinions expressed in this message are those of the
author and do not necessarily reflect those of the National Library of
Scotland. The National Library of Scotland is a registered Scottish charity. Scottish Charity No. SC011086. This message is subject to the Data Protection Act 1998
and Freedom of Information (Scotland) Act 2002 and has been
scanned by MessageLabs.
***********************************************************************