Converting State Plane Coordinates

Hello,

Have a look at spTransform (in rgdal package) and the EPSG code of the 
desired projection (this is to me the easiest way not to mess with digits and 
various copy errors that can be made while writing the projection properties) 
at www.spatialreference.org

then, you just have to do something like this

library(rgdal)

data<-read.table ("mydata.txt", h=T, sep=",") #your original dataset
coordinates(data)<-~ X + Y # where X and Y stand for the name of your lat/lon 
columns
proj4string(data)<-CRS("+init=epsg:4326")  #if your coordinates are in WGS84
data.proj<-spTransfrom(data, 
CRS("+init=epsg:the.correct.epsg.number.of.your.projection")

HTH

Alex


Le 24/08/2010 16:51, Jonathan Marc Bearak a ?crit :

Hi,

I'm new to GIS and have been trying to convert latitude and longitude 
to/from state plane coordinates.

I've tried using the project() program from the proj4 library to convert 
lat/lng to FIPS 3104 (New York State Long Island).

No matter how I go about this, however, the coordinates come out wrong. 
E.g.,
		  	"+proj=lcc +lat_1=40.66666666666666 
+lat_2=41.03333333333333 +lat_0=40.16666666666666 +lon_0=-74 +x_0=300000 
+y_0=0 +units=ft +no_defs +datum=NAD83",
		  	"+proj=lcc +a=6378137 +es=.0066943800229 +lon_0=-74 
+lat_1=41d2 +lat_2=40d40 +lat_0=40d10 +x_0=300000 +y_0=0 +units=ft +no_defs 
+datum=NAD83",

E.g., if I try the inverse, to convert 1062791, 209606.6 to lat/lng, 
project() prints:  43.04762 -76.89626.  The correct coordinates, however, 
are: 40.7416495 -073.7165681.

I've been reading the mailing lists and searching Google and R project PDFs 
and manual pages without any luck for an embarrassingly long number of 
hours without any luck.

Thanks for any help.

Best,
Jonathan