[R] converting lat-long coordinates to Albers Conical Equal Area coordinates

[Roger Bivand]

On Thu, 9 Feb 2006, jatwood wrote:

> ####################################################################################
> We have used maptools to construct state, county, township, census-tract, 
> and zipcode
> level R maps with an Albers Conical Equal Area projection.  We would like 
> to be able to
> plot the location of weather stations or other point locations on the 
> maps.  The data
> the point locations are in latitude-longitude units and we must convert the 
> coordinates
> to the Albers Conical Equal Area coordinates.
> 
> However, as of yet, we have not been able to obtain satisfactory results 
> using mapproj.
> Given the specs below can someone please tell us how to use mapproj (or 
> some other R
> library) to convert lat-long coordinates into the appropriate Albers 
> Conical Equal Area
> coordinates?

Please look in spproj on the r-spatial sourceforge site, entrance via the 
Spatial Task View on CRAN. Look for function project() and visit the proj4 
website to work out the arguments needed. 

If this isn't sufficient, please continue this thread on the R-sig-geo
mailing list.

> 
> Thanks in advance
> Joe Atwood
> Montana State University
> jatwood at montana.edu
> 
> ####################################################################################
> The material at the bottom of this message is the metadata from
> the shapefile we are using (as created in Arc-GIS).
> ####################################################################################
> 
> -----------------------------------
> Horizontal coordinate system
> Projected coordinate system name: NAD_1927_Albers
> Geographic coordinate system name: GCS_North_American_1927
> Details
> Map Projection Name: Albers Conical Equal Area
> Standard Parallel: 29.500000
> Standard Parallel: 45.500000
> Longitude of Central Meridian: -96.000000
> Latitude of Projection Origin: 23.000000
> False Easting: 0.000000
> False Northing: 0.000000
> 
> 
> Planar Coordinate Information
> Planar Distance Units: meters
> Coordinate Encoding Method: coordinate pair
> Coordinate Representation
> Abscissa Resolution: 0.008192
> Ordinate Resolution: 0.008192
> 
> 
> Geodetic Model
> Horizontal Datum Name: North American Datum of 1927
> Ellipsoid Name: Clarke 1866
> Semi-major Axis: 6378206.400000
> Denominator of Flattening Ratio: 294.978698
> _________________
> 
> Bounding coordinates
> Horizontal
> In decimal degrees
> West: -127.889829
> East: -65.349890
> North: 51.606167
> South: 22.862978
> In projected or local coordinates
> Left: -2356341.706499
> Right: 2257925.009693
> Top: 3172647.320063
> Bottom: 268329.067476
> 
> ###################################################################################
> 
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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