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Thanks Peter, this is really useful. Do you have any real-world
benchmarks for MapServer that compare regular file access with
vsicurl access, using optimized Geotifs? I've seen the tests for
GDAL at <a
href="https://trac.osgeo.org/gdal/wiki/CloudOptimizedGeoTIFF">https://trac.osgeo.org/gdal/wiki/CloudOptimizedGeoTIFF</a>,
but what about servering large map-sets over the web?<br>
<br>
<div class="moz-cite-prefix">On 8/30/2019 5:20 PM, Peter Schmitt
wrote:<br>
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<blockquote type="cite"
cite="mid:CACkcqcU+aKtwiper9zywg614YQrGpZdh1SEQcAXe32D9caN9Mg@mail.gmail.com">
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<div dir="ltr">Hi Jan,
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Aug 30, 2019 at
6:20 AM Jan Hartmann <<a
href="mailto:j.l.h.hartmann@uva.nl"
moz-do-not-send="true">j.l.h.hartmann@uva.nl</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hi Pete, could you
explain what you mean by "cloud-optimized geotiffs?<br>
</blockquote>
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<div>A Cloud Optimized GeoTIFF (COG) is a regular GeoTIFF
file in which the data is structured for fast random
access. Some properties of a COG have always been useful
for MapServer (Internally tiled & images have overview
levels). Other properties of a COG optimize for cloud
access via GDAL's /vsicurl/ virtual filesystem (Image File
Directories of the GeoTIFF are structured such that one
HTTP request can fetch all the metadata needed to read
subsequent blocks from an image). This layout has been
codified somewhat recently... Find out more here:</div>
<div><br>
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<div>1. The COGEO organization summarizes things: <a
href="https://www.cogeo.org/" moz-do-not-send="true">https://www.cogeo.org</a><br>
</div>
<div>
<div>2. This GDAL page talks about how to take a normal
GeoTIFF, make it a COG and how to validate that a given
GeoTIFF is a COG: <a
href="https://trac.osgeo.org/gdal/wiki/CloudOptimizedGeoTIFF"
moz-do-not-send="true">https://trac.osgeo.org/gdal/wiki/CloudOptimizedGeoTIFF</a></div>
3. GDAL >= 3.1 will have a new COG driver. This
provides some syntactic sugar to generating a COG in a
single gdal_translate command. <a
href="https://gdal.org/drivers/raster/cog.html"
moz-do-not-send="true">https://gdal.org/drivers/raster/cog.html</a></div>
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<div>Cheers,</div>
<div>Pete</div>
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