Converting State Plane Coordinates

On Tue, 24 Aug 2010, Alexandre Villers wrote:

   

Hey,

There is an ESRI code (ESRI:102318
<http://spatialreference.org/ref/esri/102318/>) corresponding to the
requested projection... However, I doubt CRS will take an ESRI code (Roger
?).
     

CRS("+init=esri:102318")

but the ESRI version doesn't give a +datum=, so WGS84 will be assumed. The
difference is the reversal of the +lat1= and +lat2= values, so probably
not drastic.

Roger

   

Jonathan, have a look at the rgdal and sp packages help pages for the "How
To" in CRS()

Best regards

Alex

Le 24/08/2010 17:58, Roger Bivand a ?crit :
     

On Tue, 24 Aug 2010, Alexandre Villers wrote:

       

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")
         

Looks like:

http://spatialreference.org/ref/epsg/32118/

but has some different parameters. Search on "New York" in this site for
alternatives.

Roger

       

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