[R-sig-Geo] how to rotate polygon after reading SHP file

[Roger Bivand]

On Sat, 6 Jun 2009, Jian Li wrote:

>
>
> Dear Members,
>
> if I am using readShapePoly and spTransform for producing polygons, but the result polygons are not in right position.
> How can I rotate it clockwise for example like 5??
>
> natSHP.sp <- readShapePoly("nro2.shp", proj4string=CRS("+init=epsg:26978") )
> nat2.sp <- spTransform(natSHP.sp, CRS("+proj=longlat +ellps=WGS84"))
>
> Where can I get more detail information about the different options of 
> CRS("+init=????")

IIRC, epsg:26978 appeared on analysis to be the correct description for 
your e00 file (but possibly with the wrong datum). There is absolutely no 
guarantee that this description applies to other files. Knowing the 
correct description is like knowing the correct time zone for temporal 
data, or which patient which lab slide should be associated with. It is an 
absolute requirement for the correct use of spatial data when you need to 
integrate the data with other positional information, here to align with 
Google Maps.

See:

http://spatialreference.org/

http://www.asprs.org/resources/GRIDS/

for further hints. If the original second zone Gauß-Krũger doesn't work, 
find the correct description.

Roger

PS: hint - nro2 is centred in Eastings on 0, while your earlier nat has 
its centre on 3600000; the northings differ a lot too. It doesn't feel 
like Gauß-Krũger or UTM, I'm afraid. Ask the originators of the file, and 
ask why they did not provide adequate metadata, or the nro2.prj file.

>
> Best Regards,
> Jian
>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no