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Hello,<br>
<br>
I'm trying to simplify a set of administrative boundaries that spans
over the whole northern emishpere, boundaries are:
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style=" font-family:'arial,sans-serif'; color:#000000;">xMin,yMin
-180,27.6378 : xMax,yMax 180,83.6274, CRS is 4326 WGS84. The
whole dataset comprises 100k features and 54 million vertices,
so it's quite big.<br>
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Since I have to preserve the topology, I'm using topologies to
do the simplification, as in this article:
<a class="moz-txt-link-freetext" href="http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/">http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/</a>.<br>
The simplification process uses ST_simplify, and I know that
using this function with non planar projections is not
recommended. I still get good results with 4326, even at
medium scales.<br>
However at large scales, like 1:17893297 or so (zoom level 5
to 1 on a tiled map system), there are visible artifacts. I've
tried to simplify using lambert projection <br>
(EPSG:2154) on a single country, and the results are slightly
better.<br>
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I'm not an expert of geographical projections, so I'd like to
know if there is some sort of planar projection supported by
postgis, that spans over the whole northern emisphere.<br>
Visual distortion is not an issue, my idea is to project the
whole set to this new CRS, simplify and reproject back the
results to 4326. Simplifying single countries of the dataset
using different <br>
projections is not feasible, since I have to simplify the
whole set at once to preserve the topology.<br>
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Thanks for any feedback.<br>
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Regards,<br>
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Paolo<br>
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<pre class="moz-signature" cols="72">--
Paolo Crosato
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