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

From: jatwood <jatwood_at_montana.edu>
Date: Fri 10 Feb 2006 - 06:58:31 EST


####################################################################################
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?

Thanks in advance
Joe Atwood
Montana State University
jatwood@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

###################################################################################



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri Feb 10 08:46:01 2006

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:42:27 EST