[R-sig-Geo] Changing coordinates in shapefile

[Roger Bivand]

On Sun, 5 Oct 2014, Leigh Kroeger wrote:

> Hello all,
>
> I have realised that the coordinates data in my shapefile is incorrect.

No, the description of the coordinate reference system may be incorrect. 
However, it strikes me as very unlikely that the prime meridian has been 
shifted as you describe. If the CRS is geographic not projected, it is 
very rarely the case that a non-standard prime medidian is used. 
Historically, many were used, but most are well known.

You have also thread-hopped - in your previous thread, you give a value 
of:

"+proj=cea +lat_ts=30 +ellps=WGS84"

but do not expand on what you say is Behrmann. If the shapefile was in 
projected coordinates, your units are not in degrees, so until you can 
establish authority for what you say you want to do, I'd say nothing is by 
far the best option. Establish the correct metadata for the shapefile, or 
find out from its originators what the correct metadata is.

So accept that nothing in cartography is as simple as it seems to 
non-cartographers, then that in geodetics things get an order of magnitude 
worse. To use spatial data, you either accept confusion or the need to 
spend the time it takes to get the metadata right, because everything elae 
depends on them.

Hope this clarifies,

Roger

>
> It shows coordinates that are 180 degrees off. Put simply... -140 needs 180
> added to it in each cell in column 1 to read 40.
>
> I am at a loss to understand how to add 180 to each cell. Please advise.
>
> -- 
> *Leigh A. Kroeger*
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Roger Bivand
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