[gdal-dev] GDAL2Tiles.py question

[Klokan Petr Přidal]

Hi Nathan,

 I am submitting your question to the gdal-dev mailing-list..

 > My name is Nathan and I have been looking to implement a map server for a
 > while now.  I finally was directed to your gdal2tiles.py tool by someone at
 > OpenLayers.org and am extremely thankful that I was.  I have downloaded and
 > attempted to use your tool on Windows but hit a snag.  I installed FWTools
 > and tried executing the tool on a Natural Earth map.  However, I got the
 > error: "The ordinal 2821 could not be located in the dynamic link library
 > LIBEAY32.dll" .  The shell (FWTools shell) gives the error: "ImportError:
 > DLL load failed with error code 182" .  To fix the error I ended up copying
 > libeay32.dll to the pymod directory in the FWTools install directory.  I
 > mention this to you because it is not obvious to someone with little or no
 > real python experience that it is not an issue with gdal2tiles, but rather
 > the gdal libraries.  Hope that helps someone down the line.

 It seems that the problem is really in GDAL loading this DLL library.
 I have never heard about such problem before...
 What data format is used by "Natural Earth"? I thought it is either
 JPEG or GeoTIFF.
 Can you send us the gdalinfo <inputfile> result?


 > Also, I was curious if there was a way to speed up gdal2tiles on a large
 > map…it does about a tile per second or slower at times.  And I don't know
 > much about the GDAL specification but is it possible to change the number of
 > zoom levels?

 Regarding to speed: GDAL2Tiles is highly using GDAL library, so speed
 depends on it as well, but generating one tile per second is
 horrible...
 There has to be something wrong with your setup I guess, or the
 workflow you use.
 For speed improvement during generation of tiles is better to have a
 GeoTIFF (best with internal pyramid) or a Wavelet based file as a
 source (JPEG2000,MrSID,ECW) or any other format which uses overviews.
 You can try to convert your file to one of them by gdal_translate.

 A step by step guide is described online:
 http://blog.thematicmapping.org/2008/03/generating-map-tiles-with-gdal2tiles.html


 > Thanks for a great tool!

 You are welcome...

 Klokan



 > Nathan Boettcher
 > Senior Web Developer
 > www.lawtonprinting.com