On Mon, Aug 8, 2011 at 11:06 AM, AndyC <[email protected]> wrote:
> Hi Andrea
>
> Attached are four 1km jpegs and accompanying .jgw files.
>
> https://rcpt.yousendit.com/1189606781/e17c9b5691e425ad7b00d3d51c223591
> https://rcpt.yousendit.com/1189606781/e17c9b5691e425ad7b00d3d51c223591
>
> My process was to geotiff them thus;
>
> gdal_translate -of GTiff -q -co "TILED=YES" -co COMPRESS=JPEG
> OSIM_SV8306.JPG OSIM_SV8306.tif
>
> and then build index .shp file using gdaltindex. All files are in EPSG 27700
> (British National Grid). I have also ntoiced that these "gaps" do not occur
> in the north of the projection, just in the south if that helps.

Hi Andy,
I just played with your files, but I'm getting no gaps, here are two images
I got from the files used as is, and reprojected into 4326:

http://demo.geo-solutions.it/share/nogaps_27700.jpg
http://demo.geo-solutions.it/share/nogaps_4326.jpg

I made one significant change to your conversion process though, forced
the right projection into the geotiff files:

find . -name "*.JPG" -exec gdal_translate -a_srs EPSG:27700 -of GTiff
-q -co "TILED=YES" -co COMPRESS=JPEG {} {}.tif \;

And then moved all the tiff files in their own folder.

I did not notice any gaps in the few projections I've tried, but sure the
display was slow. This is due partly to the jpeg compression (files
are smaller, but it takes more work to read them) and partly because
overviews were missing
Added the overviews to the files with the following:

find . -name "*.tif" -exec gdaladdo -r gauss {} 2 4 8 26 32 64 \;

and now it displays both properly and fast

Cheers
Andrea

-- 
-------------------------------------------------------
Ing. Andrea Aime
GeoSolutions S.A.S.
Tech lead

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Italy

phone: +39 0584 962313
fax:      +39 0584 962313

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