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<br>
TIFF has some pretty serious file size limitations so wouldn't be good
for these kinds of large rasters. I'm not familiar with TILEINDEX, but
is this a MapServer related thing? Is that applicable to local image
storage on the desktop?<br>
<br>
I think the GeoQuadTree idea is interesting - it doesn't rely on large
file support on the OS (not that that's a serious problem for any
modern OSes), and dealing with lots of small files could be more
efficient than one large file in some cases I would think.<br>
<br>
As for PNG vs JPEG, it depends on whether you're happy to accept lossy
compression or not. For many applications, customers are averse to
losing any resolution. It might make sense to make the underlying file
format in GeoQuadTree flexible acording to application. Actually, I'd
prefer to see a format that can handle multispectral files - PNG and
JPEG are both limited to 1 or 3 bands, aren't they? Or are multiple
bands stored as separate grayscale images?<br>
<br>
I would guess that with very large rasters, some sort of pyramid scheme
becomes important in addition to the tiling, so that if you just want
to get an overview of the whole image, you don't have to read every
single file. Does GeoQuadTree handle that?<br>
<br>
But, Ed is right that storing very large rasters is a not a new
problem. So, what do people do? I guess that at the high end, outfits
like Google Earth use a spatial database to organize multiple
individual raster files and then stich them together. Could somebody
outline the solution used by the Virtual Terrain project?<br>
<br>
Cheers,<br>
<br>
Sy<br>
<br>
<br>
Ed McNierney wrote:
<blockquote
cite="mid4BF377919225F449BB097CB76FFE9BC801987BAD@ptolemy.topozone.com"
type="cite">
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<div dir="ltr" align="left"><span class="804023220-14112006"><font
color="#0000ff" face="Arial" size="2">Jordi -</font></span></div>
<div dir="ltr" align="left"><span class="804023220-14112006"></span> </div>
<div dir="ltr" align="left"><span class="804023220-14112006"><font
color="#0000ff" face="Arial" size="2">You said you wanted to "avoid
the use of tile indexes or catalogues of images", but isn't that
exactly what your XML catalogue/index does? It seems that the
GeoQuadTree format is a different form of that same sort of structure.
There are several different ways of doing this now, including the
TILEINDEX mechanism, tiled TIFF files, etc. I'm sure there are
limitations to each, but I'm not sure that yet another tiling scheme
will help.</font></span></div>
<div dir="ltr" align="left"><span class="804023220-14112006"></span> </div>
<div dir="ltr" align="left"><span class="804023220-14112006"><font
color="#0000ff" face="Arial" size="2">In particular, PNG is not the
best format for all images, and it's important to support other
encoding mechanisms, especially JPEG. Photographic images are huge
when stored in PNG format, and JPEG is usually a much better choice.
Conversely, scanned line art and synthetic images generally compress
and store better as PNG images.</font></span></div>
<div dir="ltr" align="left"><span class="804023220-14112006"></span> </div>
<div dir="ltr" align="left"><span class="804023220-14112006"> <font
color="#0000ff" face="Arial" size="2">- Ed</font></span></div>
<div dir="ltr" align="left"><span class="804023220-14112006">
<p><font size="2">Ed McNierney<br>
President and Chief Mapmaker<br>
TopoZone.com / Maps a la carte, Inc.<br>
73 Princeton Street, Suite 305<br>
North Chelmsford, MA 01863<br>
<a class="moz-txt-link-abbreviated" href="mailto:ed@topozone.com">ed@topozone.com</a><br>
(978) 251-4242 </font></p>
</span></div>
<br>
<div class="OutlookMessageHeader" dir="ltr" align="left" lang="en-us">
<hr tabindex="-1"><font face="Tahoma" size="2"><b>From:</b>
<a class="moz-txt-link-abbreviated" href="mailto:gdal-dev-bounces@lists.maptools.org">gdal-dev-bounces@lists.maptools.org</a>
[<a class="moz-txt-link-freetext" href="mailto:gdal-dev-bounces@lists.maptools.org">mailto:gdal-dev-bounces@lists.maptools.org</a>] <b>On Behalf Of </b>Brent
Fraser<br>
<b>Sent:</b> Tuesday, November 14, 2006 3:05 PM<br>
<b>To:</b> Jordi Gilabert Vall; <a class="moz-txt-link-abbreviated" href="mailto:gdal-dev@lists.maptools.org">gdal-dev@lists.maptools.org</a><br>
<b>Subject:</b> Re: [Gdal-dev] GeoQuadTree - an open format for
storinggeoreferencedimages<br>
</font><br>
</div>
<div><font size="2">For those interested tiling,</font></div>
<div> </div>
<div><font size="2"> There is similar tiling related discussion/work
going on at:</font></div>
<div> </div>
<div><font size="2"> <a
href="http://lists.eogeo.org/mailman/listinfo/tiling"><font size="3">http://lists.eogeo.org/mailman/listinfo/tiling</font></a> (do
they have a web page?)</font></div>
<div> </div>
<div><font size="2"> and </font></div>
<div><font size="2"> <a
href="http://www.stereofx.org/terrain.html">http://www.stereofx.org/terrain.html</a>,
implemented in <a href="http://vterrain.org/">http://vterrain.org/</a>,
particularly VTBuilder (<a
href="http://vterrain.org/Doc/VTBuilder/overview.html">http://vterrain.org/Doc/VTBuilder/overview.html</a>)</font></div>
<div> </div>
<div><font size="2">Brent Fraser</font></div>
<blockquote
style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;">
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">-----
Original Message ----- </div>
<div
style="background: rgb(228, 228, 228) none repeat scroll 0%; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>From:</b>
<a title="jordi@geoquadtree.org" href="mailto:jordi@geoquadtree.org">Jordi
Gilabert Vall</a> </div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>To:</b>
<a title="gdal-dev@lists.maptools.org"
href="mailto:gdal-dev@lists.maptools.org">gdal-dev@lists.maptools.org</a>
</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Sent:</b>
Tuesday, November 14, 2006 3:25 AM</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Subject:</b>
[Gdal-dev] GeoQuadTree - an open format for storing georeferencedimages</div>
<div><br>
</div>
Hi,<br>
<font face="Arial, sans-serif"><font size="2"><br>
Some time ago I needed the retrieval from very large georeferenced
raster images in a OGC WMS server, and I wanted to avoid the use of
tile indexes or catalogues of images, neither a database. I started
thinking of an open format for storing arbitrarily large georeferenced
images. I named this format "GeoQuadTree", as it would be based on a
quadtree of rectangular tiles, each in PNG format on the filesystem, in
a simple hierarchical structure of folders. I wrote a command line
utility for creating it, importing from PNG/JPEG/TIFF and exporting to
PNG/JPEG/TIFF/GDAL. I also wrote a GDAL driver for this format. I
tested successfully with my own WMS server software, and on MapServer
compiled with GDAL support. It worked very well on Blue Marble Next
Generation at a resolution of 15 arc-seconds, i.e. 86400x43200 pixels.</font></font>
<p style="margin-bottom: 0cm;"><font face="Arial, sans-serif"><font
size="2">You can find more information on the project web site:</font></font></p>
<p style="margin-bottom: 0cm; margin-left: 40px;"><font
face="Arial, sans-serif"><font size="2"><a
onclick="return top.js.OpenExtLink(window,event,this)"
href="http://geoquadtree.org/" target="_blank">http://geoquadtree.org/
</a></font></font></p>
<p style="margin-bottom: 0cm;"><font face="Arial, sans-serif"><font
size="2">I'm testing the release 1.0.0, you can test it on the
subversion repository if you want (I haven't packaged it yet).<br>
</font></font></p>
<p style="margin-bottom: 0cm;"><font face="Arial, sans-serif"><font
size="2">I think it's a useful format, open, very easy to use, and
very efficient (in terms of response time).</font></font></p>
<p style="margin-bottom: 0cm;"><font face="Arial, sans-serif"><font
size="2">Do you think it could be useful for you ? Would you like to
include it on GDAL's next release ?</font></font></p>
<span class="sg">
<p style="margin-bottom: 0cm;"><font face="Arial, sans-serif"><font
size="2">jordi at geoquadtree org</font></font></p>
</span>
<p> </p>
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