[R-sig-Geo] mapproject - datum and units

[Michael Sumner]

Hello, what datum and unit is used by the mapproject function?

I'm trying to georegister the coordinates returned by mapproject() in a 
GIS (Manifold). 

I'm using

proj='azequalarea',orient=c(-36.92,174.6,0)

as in the map.grid example for New Zealand.

Assuming the coordinate system "Lambert Azimuthal Equal Area", on datum 
"World Geodetic (1984)", I can get the registration close (within 100 
km) by using a local scale of 10, 000 km - however this procedure is 
quite ad hoc, and I'd like to know more about how this is specified in R. 
(See xml below for my "close" registration by changing the scale).

I'm quite sure that the unit and datum details are not specified in the 
documentation for mapproject, and I can't find them in the source code 
(but I'm a bit lost there anyway). 

Cheers, Mike.


<?xml version="1.0" encoding="UTF-8"?>
<preset>
   <name>Lambert Azimuthal Equal Area</name>
   <datum>World Geodetic 1984 (WGS84)</datum>
   <system>Lambert Azimuthal Equal Area</system>
   <unit>Kilometer</unit>
   <majorAxis>6.378137000000000000000000e+006</majorAxis>
   <eccentricity>8.181919084262148600000000e-002</eccentricity>
   <centerX>0.000000000000000000000000e+000</centerX>
   <centerY>0.000000000000000000000000e+000</centerY>
   <centerZ>0.000000000000000000000000e+000</centerZ>
   <scaleX>1.000000000000000000000000e+000</scaleX>
   <localScaleX>1.000000000000000000000000e+007</localScaleX>
   <scaleY>1.000000000000000000000000e+000</scaleY>
   <localScaleY>1.000000000000000000000000e+007</localScaleY>
   <falseEasting>0.000000000000000000000000e+000</falseEasting>
   <localOffsetX>0.000000000000000000000000e+000</localOffsetX>
   <falseNorthing>0.000000000000000000000000e+000</falseNorthing>
   <localOffsetY>0.000000000000000000000000e+000</localOffsetY>
   <centerLat>-3.692000000000000200000000e+001</centerLat>
   <centerLon>1.745999999999999900000000e+002</centerLon>
</preset>