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Mapproj package (mapproject) problems

I've had some problems getting `mapproject()` in the mapproj
package in R to give me the same projection as one gets from `PROJ.4`
or ArcGIS. Basically, I can't get the same projected coordinates in
mapproject as I do with the standard packages.

For example, I'd like to project with the Albers projection, with
central meridian -96, standard parallels 29.5 and 45.5, and latitude
of origin 23.0, with false_easting and false_northing both zero,
and units of meters. In mapproject, I can use `orientation=c(90,0,-96)`
or `orientation=c(90,-96,0)`, and it will put the central meridian
at -96 but I have no control over where y=0 falls (which I think should
be based on the latitude of origin) nor of the scaling of the projection.
Using one of the orientations above, the Albers projection in mapproject
is a linear transformation of the true Albers projection (-96,29.5,45.5,23).
If anyone understands better what `mapproject()` is doing and
how to control it, I'd love to hear it.

A solution to this is to explicitly use `PROJ.4`; this could
even be done within R by using the `system()` function, but
of course requires that you have `PROJ.4` on your machine.

Last modified: 6/23/07.

** Next:** Database type operations
** Up:** Spatial and spatio-temporal data
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Chris Paciorek
2012-01-21