[Geoserver-users] can gdal2tiles be used?

GeoServer GeoServer User
1

Can the tile structure (TMS?) generated by gdal2tiles.py be
used with geoserver?

I have geoserver serving a geotiff image at various zoom
levels, but the image is not as sharp as those produced by
gdal2tiles+openlayers. gdal2tiles produces a
tilemapresource.xml file with lots of interesting elements
in it. Can that be used as input (data store?) to
geoserver? Or do I need to switch over to tilecache? Will
tilecache + geoserver produce better resolution that
geoserver alone, or does that just increase performance and
not resolution?

Thanks,

Wendell

2

Wendell Turner wrote:

Can the tile structure (TMS?) generated by gdal2tiles.py be
used with geoserver?

I have geoserver serving a geotiff image at various zoom
levels, but the image is not as sharp as those produced by
gdal2tiles+openlayers. gdal2tiles produces a
tilemapresource.xml file with lots of interesting elements
in it. Can that be used as input (data store?) to
geoserver?

Not as far as I know, thought a code contribution to read
that format too is always appreciated :wink:

Or do I need to switch over to tilecache? Will
tilecache + geoserver produce better resolution that
geoserver alone, or does that just increase performance and
not resolution?

About the resolution, it may just be that GeoServer is doing
nearest neighbour interpolation. Can you try 1.7.0-beta1 (which,
raster wise, works better than 1.6.x series) and
enable bilinear interpolation to get best quality output?

Cheers
Andrea

3

On Thu, Jun 19, 2008 at 09:21:49AM +0200, Andrea Aime wrote:

Wendell Turner wrote:

Can the tile structure (TMS?) generated by gdal2tiles.py be
used with geoserver?

I have geoserver serving a geotiff image at various zoom
levels, but the image is not as sharp as those produced by
gdal2tiles+openlayers. gdal2tiles produces a
tilemapresource.xml file with lots of interesting elements
in it. Can that be used as input (data store?) to
geoserver?

Not as far as I know, thought a code contribution to read
that format too is always appreciated :wink:

Oops. I didn't mean to volunteer for work(!). However, how
hard would it be for geoserver to use the TMS hierarchy as
input?

Or do I need to switch over to tilecache? Will
tilecache + geoserver produce better resolution that
geoserver alone, or does that just increase performance and
not resolution?

About the resolution, it may just be that GeoServer is doing
nearest neighbour interpolation. Can you try 1.7.0-beta1 (which,
raster wise, works better than 1.6.x series) and
enable bilinear interpolation to get best quality output?

Stock 1.7.0-beta1 showed no appreciable difference. How do
I force bilinear interpolation? The coverage Editor has:
   Default Int. Method: nearest neighbor
   Interpolation Methods: nearest neighbor,bilinear,bicubic
but the fields don't seem to be editable. Do I need to turn
off nearest neighbor to get bilinear to be used?

Thanks,

Wendell

4

Apologies for accidentally replying off-list.

My suggestion was that you can do the mosaic on the client-side in
OpenLayers-- if you only have about a handful of layers, it works
fairly well and is easy to setup.

It would be worthwhile to eventually add TMS support into GeoWebCache in order to have a bit more feature parity with TileCache.

GeoWebCache? That one is new to me. Is that what Geoserver
uses internally?

No, it more closely resembles a Java version of Tilecache, with
slightly different features. See:
http://geowebcache.org/

To add to that and respond to your original question, moving to
TileCache / GeoWebCache doesn't really help your situation if you are
already dealing with pre-generated tiles such as the gdal2tiles
output.

-- Chris Whitney

On Thu, Jun 19, 2008 at 2:11 PM, Wendell Turner <wendell@anonymised.com> wrote:

On Thu, Jun 19, 2008 at 01:34:33PM -0700, Chris Whitney wrote:

What do you see as the advantage for using the gdal2tiles output as an
input for Geoserver?

The images produced by gdal2tiles are much sharper/clearer.
The tiles produced by GeoServer are slightly fuzzy when
zoomed in to the same level.

If you are using OpenLayers,

Yes, and that part is working very well.

why not add the TMS
layer in OpenLayers, and then add the Geoserver layers to OpenLayers
as well?

The template html file that gdal2tiles.py output was
pixel-based. I tried to switch to lat/lng, but couldn't
figure out the maxResolution, pixelSize, and other
parameters to make it work correctly.

It would be worthwhile to eventually add TMS support into GeoWebCache

GeoWebCache? That one is new to me. Is that what Geoserver
uses internally?

in order to have a bit more feature parity with TileCache. But if all
you need to do is serve up a static GeoTiff with zoom levels, I don't
see why you wouldn't use the gdal2tiles output directly.

Mostly because I don't know what I'm doing. In my stumbling
around, my knowledge of geo-spatial tools amounts to this:

OpenLayers - nice
gdal2tiles.py - nice crisp tiles, but couldn't change from
  pixel-based to latlon-based, also can't mosaic multiple
  maps
mapserver - never could get it to work with proj4, so only
got the simple examples to run
geoserver - images not as nice as gdal2tile, but is lat-lon
based, and will probably be needed to stitch/mosaic
multiple maps together
MosaicIndexBuilder - needed to make geoserver mosaic
multiple maps, but have not been able to compile/run it
yet

If there are better/more appropriate tools that would work
please let me know.

Thank you for your response.

Wendell