[R-sig-Geo] Converting State Plane Coordinates

[Alexandre Villers]

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 écrit :
> 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
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