Hey again,<br><br>thanks for so many interesting comments! the problem with defining my projection is that i do not know the actual LineString before buffering. It can be from france to usa, or from france to sweden and then to usa (the LineStrings are flight routes and might change). So i think the only suitable solution for me is to split the LineString into single LineStrings fitting different UTM zones and do a union on those in wgs84. but i think i will get a buffer with gaps in it.. hmm. not the best but a working solution!<br>
<br>regards,<br>Matthes<br><br><br><div class="gmail_quote">2009/2/11 Stefan Steiniger <span dir="ltr"><<a href="mailto:sstein@geo.uzh.ch">sstein@geo.uzh.ch</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
As I am not on the postgis list I answer directly to Matthes,<br>
<br>
the solution is - maybe - simple.<br>
Define your own projection and buffer there. I would say it should be a Cylindric Projection (Oblique Mercator) which is touching/based on the great circle that runs between both cities. It would be similar to the swiss projection but with different origin and different azimuth:<br>
<a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/projections.html" target="_blank">http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/projections.html</a><br>
<br>
ok.. maybe it isn't that simple and it will take a few days to realize that ;)<br>
<br>
stefan<br>
<br>
PS: thanks Martin for making aware<br>
<br>
PPS: I wonder if I did write a long time pseudo code in Mathcad to display the distortion of circles due to the UTM projection. But I may be wrong and it have been something else.<br>
<br>
Martin Davis wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Check out this thread on the PostGIS list for more interesting discussion on this topic.<br>
<br>
I wonder how Oracle would handle the USA-to-France buffer? Not well, I'm betting...<div class="Ih2E3d"><br>
<br>
-------- Original Message --------<br>
Subject: Re: [postgis-users] Using a buffer with a LineString covering the whole world<br>
Date: Wed, 11 Feb 2009 08:58:16 -0800<br>
From: Paul Ramsey <<a href="mailto:pramsey@opengeo.org" target="_blank">pramsey@opengeo.org</a>><br>
Reply-To: PostGIS Users Discussion <<a href="mailto:postgis-users@postgis.refractions.net" target="_blank">postgis-users@postgis.refractions.net</a>><br>
To: PostGIS Users Discussion <<a href="mailto:postgis-users@postgis.refractions.net" target="_blank">postgis-users@postgis.refractions.net</a>><br>
References: <<a href="mailto:1e3d99e40902110826m45a27717j3780bac013f0e31b@mail.gmail.com" target="_blank">1e3d99e40902110826m45a27717j3780bac013f0e31b@mail.gmail.com</a>><br>
<br>
<br>
<br>
I find running screaming into the hills helps.<br>
<br>
Sorry, that's the use case (really large/long things) where there just<br>
is no proper solution except to start writing code that works on a<br>
sphere. Most things just aren't that long/large. But a few are. I<br>
would love it if someone/manyones would express their interest in<br>
funding such a development.<br>
<br>
Want a hack? Cut your line into 1000 smaller lines. Buffer all those<br>
individually in a planar space. The union them all back together<br>
again, in lon/lat.<br>
<br></div>
P.<br>
<br><div class="Ih2E3d">
On Wed, Feb 11, 2009 at 8:26 AM, Matthes Rieke<br>
<<a href="mailto:matthes.rieke.01@gmail.com" target="_blank">matthes.rieke.01@gmail.com</a>> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi all,<br>
<br>
I am currently running into this problem: I have a LineString in lat/long<br>
coordinates (SRID 4326 - going from USA to france). I now want to create a<br>
buffer in meters from this. So the normal way to transfrom the coordinates<br>
to a planar CRS, buffering, then transforming back to 4326 does not work<br>
(the Line is covering many UTM zones). What would be a reasonable solution<br>
for this problem?<br>
<br>
Thanks and regards,<br>
Matthes<br>
<br>
_______________________________________________<br>
postgis-users mailing list<br>
<a href="mailto:postgis-users@postgis.refractions.net" target="_blank">postgis-users@postgis.refractions.net</a><br>
<a href="http://postgis.refractions.net/mailman/listinfo/postgis-users" target="_blank">http://postgis.refractions.net/mailman/listinfo/postgis-users</a><br>
<br>
<br>
</blockquote>
_______________________________________________<br>
postgis-users mailing list<br>
<a href="mailto:postgis-users@postgis.refractions.net" target="_blank">postgis-users@postgis.refractions.net</a><br>
<a href="http://postgis.refractions.net/mailman/listinfo/postgis-users" target="_blank">http://postgis.refractions.net/mailman/listinfo/postgis-users</a><br>
<br>
<br>
<br>
</div></blockquote>
</blockquote></div><br>