[gdal-dev] gdal2tiles strangeness

Fri Apr 3 19:24:52 EDT 2009

Hi Klokan,

Thanks for all your help on this. The steps you outlined are very
similar to what I tried originally. Even with the new gdal2tiles.py,
and following your instructions exactly, I get the same result. When I
open the doc.kml it looks great. But when you zoom out, the tiles
shift to what I believe are projected images.

Adding -p geodetic does fix the problem, but it would be nice to
figure out if this is a bug and then fix it.

Mano

2009/4/3 Klokan Petr Přidal <klokan at klokan.cz>:
> Dear Mano,
>
> You are right, gdal2tiles.py in stable GDAL 1.6 has a bug for KML
> generation in "-p raster", which is now fixed in gdal-trunk as well as
> in maptiler SVN...
>
> Here is it step by step for your process:
>
> - Download the latest gdal2tiles from gdal-trunk or maptiler svn and
> save it on your disk:
> http://maptiler.googlecode.com/svn/trunk/maptiler/gdal2tiles.py
>
> - Download the "world.200401.3x21600x10800.jpg" (or any other world map):
> http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php
>
> - Assign georeference and srs:
> gdal_translate -of vrt -a_srs epsg:4326 -a_ullr -180 90 180 -90
> world.200401.3x21600x10800.jpg world.vrt
>
> - Create 'raster' tiles (it will automatically generate KML, because
> input is epsg:4326):
> python ./gdal2tiles.py -p raster world.vrt
>
> Open doc.kml in Google Earth...  ;-)
>
> If you don't want to update the gdal2tiles utility and you need
> workflow with stable GDAL 1.6 then use:
>
> gdal2tiles -p geodetic world.vrt
>
> It will generate you correct KML for Google Earth directly and viewer
> compatible with OpenLayers base map and other WMS, WMS-C, and TMS
> services, but your map will be resampled to one of the fixed map
> scales - according the TMS Global Geodetic profile definition:
> http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification
>
> Best regards,
>
> Klokan
>
> 2009/4/3 Mano Marks <mmarks at google.com>:
>> So, using -p "raster" creates far worse distortion in the KML. I'm back to
>> not using it. I get distortion only at the highest zoom levels that way.
>>
>> 2009/4/1 Klokan Petr Přidal <klokan at klokan.cz>
>>>
>>> Mano,
>>>
>>> > Thanks for the pointer. So it looks like, right now, there's a bug in
>>> > gdal2tiles, according to  Jesse? Any news on when that might be fixed?
>>>
>>> Just use this gdal2tiles.py:
>>> http://maptiler.googlecode.com/svn/trunk/maptiler/gdal2tiles.py
>>>
>>> The issue he is referring is fixed in MapTiler SVN:
>>> http://code.google.com/p/maptiler/issues/detail?id=9
>>> Commited in maptiler SVN in r17 on Mar 20, 2009.
>>>
>>> I am proposing to fix all known bugs during this summer as part of
>>> Google Summer of Code project, and also implement support for OGC WMTS
>>> standard, publish a stable version of MapTiler
>>> (http://www.maptiler.org/) and synchronize the code with GDAL SVN.
>>>
>>> Klokan
>>>
>>> >
>>> > Mano
>>> >
>>> > 2009/3/31 Klokan Petr Přidal <klokan at klokan.cz>:
>>> >> Mano,
>>> >>
>>> >> If you would like to have both Google Maps and Google Earth
>>> >> presentation for a global map then you must generate two tile sets,
>>> >> because Google Maps supports only Mercator tiles (EPSG:900913) and
>>> >> Google Earth only geodetic (EPSG:4326).
>>> >>
>>> >> GDAL2Tiles has as a default tile profile 'mercator', it means that it
>>> >> will warp your input into Spherical Mercator internally.
>>> >> To create tiles and KML for Google Earth for your EPSG:4326 input data
>>> >> you should use -p "raster".
>>> >>
>>> >> From the "gdal2tiles --help":
>>> >>
>>> >> -k, --force-kml     Generate KML for Google Earth - default for
>>> >> 'geodetic'
>>> >>                        profile and 'raster' in EPSG:4326. For a dataset
>>> >> with
>>> >>                        different projection use with caution!
>>> >>
>>> >> Detailed description of recommended step by step usage of gdal2tiles
>>> >> for global maps was posted by Jesse Varner
>>> >> from CIRES & NOAA/NGDC, who used gdal2tiles for official presentation
>>> >> of Global magnetic anomaly map EMAG2 (for Google Maps/Earth) at:
>>> >> http://ngdc.noaa.gov/geomag/data/Google_Maps/EMAG2/index.html
>>> >>
>>> >> His post is here:
>>> >> http://groups.google.com/group/maptiler/msg/fe105e27a62711e4
>>> >>
>>> >> Best regards,
>>> >>
>>> >> Klokan
>>> >>
>>> >> On Tue, Mar 31, 2009 at 6:37 PM, Mano Marks <mmarks at google.com> wrote:
>>> >>> I'm getting started with gdal2tiles, and I'm getting strange results.
>>> >>>
>>> >>> I downloaded a blue marble jpg from NASA:
>>> >>> http://www.nasa.gov/vision/earth/features/blue_marble.html
>>> >>>
>>> >>> And I ran the following command lines:
>>> >>>
>>> >>> gdal_translate -of VRT -a_srs EPSG:4326 -gcp 0 0 -180 90 -gcp 21600 0
>>> >>> 180 90 -gcp 21600 10800 180 -90 world_200401.jpg bluemarble1.vrt
>>> >>>
>>> >>> gdalwarp -of VRT -t_srs EPSG:4326 bluemarble1.vrt bluemarble2.vrt
>>> >>>
>>> >>> gdal2tiles -k bluemarble2.vrt
>>> >>>
>>> >>> Of course, the last step took awhile.
>>> >>>
>>> >>> The Google Maps and OpenLayers output was fine. However, the KML had
>>> >>> some odd results. When loaded directly, it looked fine, but when I
>>> >>> zoomed out, it appeared that what was the equivalent of zoom 0 and 1
>>> >>> the images retain a Mercator projection. Is this a known issue, or did
>>> >>> I do something wrong?
>>> >>>
>>> >>> --
>>> >>> Mano Marks
>>> >>> Geo Developer Advocate
>>> >>> Google, Inc.
>>> >>> mmarks at google.com
>>> >>> http://twitter.com/ManoMarks
>>> >>> _______________________________________________
>>> >>> gdal-dev mailing list
>>> >>> gdal-dev at lists.osgeo.org
>>> >>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>> >>>
>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> http://blog.klokan.cz/
>>> >> http://www.maptiler.org/
>>> >> http://www.oldmapsonline.org/
>>> >>
>>> >
>>> >
>>> >
>>> > --
>>> > Mano Marks
>>> > Geo Developer Advocate
>>> > Google, Inc.
>>> > mmarks at google.com
>>> > http://twitter.com/ManoMarks
>>> >
>>>
>>>
>>>
>>> --
>>> http://blog.klokan.cz/
>>> http://www.maptiler.org/
>>> http://www.oldmapsonline.org/
>>
>>
>>
>> --
>> Mano Marks
>> Geo Developer Advocate
>> http://twitter.com/ManoMarks
>> Join me for Google I/O, Google's biggest Developer Conference, in San
>> Francisco, May 27th and 28th, 2009
>> http://code.google.com/events/io/
>>
>>
> --
> http://blog.klokan.cz/
> http://www.maptiler.org/
> http://www.oldmapsonline.org/
>

-- 
Mano Marks
Geo Developer Advocate
http://twitter.com/ManoMarks
Join me for Google I/O, Google's biggest Developer Conference, in San
Francisco, May 27th and 28th, 2009
http://code.google.com/events/io/