Even,
Thanks for the possible algorithm.... but to be honest: some sort of
command line switch would be /somewhat more handy/, for non-programmers
like me.
Hermann
Even Rouault wrote:
Selon Hermann Peifer <[email protected]>:
I think this should be prefectly doable with some code/script just using OGR
API.
Here's a possible algorithm :
1) Create a new empty WGS84 shapefile
1) Loop over features in the source shapefile (the one after reprojection to
WGS84)
2a) If the polygon has points with longitudes both near 180° and near -180°,
create a duplicate temporary polygon and add 360° to the negative longitudes.
Compute the interescection with Geometry.Intersect (you need GEOS support) of
that polygon with POLYGON((0 90,180 90,180 -90,0 -90,0 90)) and with
POLYGON((180 90,360 90,360 -90,180 -90,180 90)). For the second intersection,
substract 360° to the longitudes in order to get again longitudes in the
[-180,180] range. Finally, write 2 new features into the output shapefile, or
better, just one with the geometry being a multipolygon with the 2 parts.
2b) Otherwise, just copy the original feature into the output shapefile
Best regards,
Even
Eric,
I can't help much apart from confirming that the same happened to me
when trying to reproject Russia from LAEA to WGS84.
My "solution" was to ask a colleague, who is using ESRI products to do
me a favour... :-(
Hermann
Eric Muller wrote:
I am trying to reproject shapefiles that represent Russia (from
http://wagda.lib.washington.edu/DATA/geography/world/russia/download.html)
from the original:
The map is Albers equal-area projection Clarke spheroid of1866 with
the first standard parallel 46 00 0.000, the second standard
parallel 73 00 0.000, the central meridian 84 00 0.000. The latitude
of the projection's origin is 60 00 0.000. Units -- meters.
to lat/long WGS84. I use the following command:
ogr2ogr \
-s_srs '+proj=aea +ellps=clrk66 +lat_1=46.0 +lat_2=73.0 +lat_0=60.0
+lon_0=84.0 +units=m +no_defs' \
-t_srs '+proj=latlong +ellps=WGS84 +datum=WGS84 +no_defs' \
rs_polbnda_${f}.shp rus${f}.shp
I would like polygons that cross the 180 degree longitude to be split.
It there a way to ask ogr2ogr to do that? What is the recommended way to
do it, if not?
Thanks,
Eric.
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