[Geoserver-users] ECW alternatives

[dead passive]

Hi,
I've been given an .ecw file of about 16gb containing an aerial photography
mosaic. I wish to use this data for WMS and WCS, but GeoServer does not
support ecw. I've tried converting to GeoTiff, but have to reduce the
quality to 6% of the original to get an a GeoTiff below the 4gb maximum!
Is there an alternative that allows me to keep the original quality of the
file?
Thanks,
Jon

[a***@openplans.org]

Post by dead passive
Hi,
I've been given an .ecw file of about 16gb containing an aerial
photography mosaic. I wish to use this data for WMS and WCS, but
GeoServer does not
support ecw. I've tried converting to GeoTiff, but have to reduce the
quality to 6% of the original to get an a GeoTiff below the 4gb maximum!
Is there an alternative that allows me to keep the original quality of
the file? Thanks,

First of all, GeoSolutions is setting up ECW support for GeoServer and I've
seen a demo of it at FOSS4G, but afaik it's still not ready for prime time.
One way to speed up the inclusion in the standard GeoServer would be to
throw some funding at them.

As an alternative, I'd suggest to use gdal_translate to create a set
of geotiff images, that is, a regular mosaic. If you compress them
with jpeg compression, tile them, and add overviews, you should be
able to get good speed with just a few tiles (the tiles will have to
be put togheter using the mosaic plugin).

We have some directions on the GeoServer user guide about how to
use gdal_translate and the other gdal tools to create the tiles
and then the mosaic.

Hope this helps
Cheers
Andrea

[dead passive]

Post by a***@openplans.org

Post by dead passive
Hi,
I've been given an .ecw file of about 16gb containing an aerial
photography mosaic. I wish to use this data for WMS and WCS, but
GeoServer does not
support ecw. I've tried converting to GeoTiff, but have to reduce the
quality to 6% of the original to get an a GeoTiff below the 4gb maximum!
Is there an alternative that allows me to keep the original quality of
the file? Thanks,

First of all, GeoSolutions is setting up ECW support for GeoServer and I've
seen a demo of it at FOSS4G, but afaik it's still not ready for prime time.
One way to speed up the inclusion in the standard GeoServer would be to
throw some funding at them.
As an alternative, I'd suggest to use gdal_translate to create a set
of geotiff images, that is, a regular mosaic. If you compress them
with jpeg compression, tile them, and add overviews, you should be
able to get good speed with just a few tiles (the tiles will have to
be put togheter using the mosaic plugin).
We have some directions on the GeoServer user guide about how to
use gdal_translate and the other gdal tools to create the tiles
and then the mosaic.
Hope this helps
Cheers
Andrea

Thanks for the information.
Wouldn't using jpeg compression on the GeoTiff files loose quality from the
original .ecw file? I don't really want to loose any quality in the
conversion process (I know .ecw is lossy, I don't really want to loose any
more!)
Also, I would like to carry out analysis such as change detection on the
resulting GeoTiff. Do you know if it being compressed using JPEG would have
any funny effects?
Thanks!
Jon

[Rahkonen Jukka]

-----Original Message-----

Post by dead passive
Thanks for the information.
Wouldn't using jpeg compression on the GeoTiff files loose quality from the
original .ecw file? I don't really want to loose any quality in the
conversion process (I know .ecw is lossy, I don't really want to loose any
more!)
Also, I would like to carry out analysis such as change detection on the
resulting GeoTiff. Do you know if it being compressed using JPEG would have
any funny effects?
Thanks!
Jon

Hi,

You are naturally right, lossy compression degrades quality. If you don't want to loose any of what you have left, you can decompress the ecw files to uncompressed tiff tiles and use those through image mosaic. You'll pay for that in disk space. There are other Open source WMS servers that can utilize ECW format quite effectively, for example UMN MapServer, but if you prefer GeoServer then I guess you'd better take the uncompressed TIFF image mosaic way while waiting for the coming ECW support.

-Jukka Rahkonen-

[dead passive]

Post by Rahkonen Jukka
-----Original Message-----

Post by dead passive
Thanks for the information.
Wouldn't using jpeg compression on the GeoTiff files loose quality from the
original .ecw file? I don't really want to loose any quality in the
conversion process (I know .ecw is lossy, I don't really want to loose any
more!)
Also, I would like to carry out analysis such as change detection on the
resulting GeoTiff. Do you know if it being compressed using JPEG would have
any funny effects?
Thanks!
Jon

Hi,
You are naturally right, lossy compression degrades quality. If you don't
want to loose any of what you have left, you can decompress the ecw files
to uncompressed tiff tiles and use those through image mosaic. You'll pay
for that in disk space. There are other Open source WMS servers that can
utilize ECW format quite effectively, for example UMN MapServer, but if
you prefer GeoServer then I guess you'd better take the uncompressed TIFF
image mosaic way while waiting for the coming ECW support.
-Jukka Rahkonen-

Does ecw compress by a relatively fixed ratio? If so, how much space should
I expect my GeoTiff files to be given that the ecw is 16gb? I'm guessing
they would be very large indeed.
Thanks,
Jon

[a***@openplans.org]

Post by dead passive
Does ecw compress by a relatively fixed ratio? If so, how much space
should I expect my GeoTiff files to be given that the ecw is 16gb? I'm
guessing they would be very large indeed. Thanks,
Jon

I don't know if the ratio is fixed, but I can tell you a 300MB
ecw turned into a 20GB uncompressed geotiff set (8 files in my case).
Anyways, if you compress them with jpeg compression the end result
should not be that much bigger than ECW (twice as much?).
Just remember to tile, jpeg compress, and then add overviews.

let me know how things go (and maybe try with a first tile that's
1/10th or so of the initial area, and see how big it gets, and how
fast GeoServer renders it)
Cheers
Andrea

[dead passive]

Post by a***@openplans.org

Post by dead passive
Does ecw compress by a relatively fixed ratio? If so, how much space
should I expect my GeoTiff files to be given that the ecw is 16gb? I'm
guessing they would be very large indeed. Thanks,
Jon

I don't know if the ratio is fixed, but I can tell you a 300MB
ecw turned into a 20GB uncompressed geotiff set (8 files in my case).
Anyways, if you compress them with jpeg compression the end result
should not be that much bigger than ECW (twice as much?).
Just remember to tile, jpeg compress, and then add overviews.
let me know how things go (and maybe try with a first tile that's
1/10th or so of the initial area, and see how big it gets, and how
fast GeoServer renders it)
Cheers
Andrea

I'm trying to use JPEG compression with the following command

gdal_translate -of GTiff -co "TILED=YES" -co "COMPRESS=JPEG" -co
"JPEG_QUALITY=100" -projwin 145000 397000 250500 280500
AerialPhotographyRGB2006.ecw topleft.tif

but this is causing the following error:

ERROR 1: JPEGLib:JPEG parameter struct mismatch: library thinks size is 376,
caller expects 360
ERROR 1: JPEGLib:Improper call to JPEG library in state 0

Any idea why this is? I'm on Window using FWTools binaries.
Thanks,
Jon

[Rahkonen Jukka]

-----Original Message-----

Post by dead passive
I'm trying to use JPEG compression with the following command
gdal_translate -of GTiff -co "TILED=YES" -co "COMPRESS=JPEG" -co
"JPEG_QUALITY=100" -projwin 145000 397000 250500 280500
AerialPhotographyRGB2006.ecw topleft.tif
ERROR 1: JPEGLib:JPEG parameter struct mismatch: library thinks size is 376,
caller expects 360
ERROR 1: JPEGLib:Improper call to JPEG library in state 0
Any idea why this is? I'm on Window using FWTools binaries.

Hi,

I have never used JPEG compression with tiff files, but for me your
command seems to be OK. Verify it by running it without jpeg options
and check if the resulting uncompressed tiff is good. After that you
can ask advice from gdal-dev mailing list.

-Jukka-

[Andrew Hughes]

My advice for ECW is mapserver+gdal+the ecw sdi on WINDOWS. I tried this on
linux and had all the trouble in the world and gave up.

Apparently it is much easier on windows... and I know ER Mapper are
typically a windows shop.

Post by dead passive
Hi,
I've been given an .ecw file of about 16gb containing an aerial photography
mosaic. I wish to use this data for WMS and WCS, but GeoServer does not
support ecw. I've tried converting to GeoTiff, but have to reduce the
quality to 6% of the original to get an a GeoTiff below the 4gb maximum!
Is there an alternative that allows me to keep the original quality of the
file?
Thanks,
Jon
--
http://www.nabble.com/ECW-alternatives-tf4555355.html#a13000518
Sent from the GeoServer - User mailing list archive at Nabble.com.
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