Great! That's exactly what I am looking for. Thank a million!

Dazhi

On Fri, Oct 29, 2010 at 12:21 PM, Barry Rowlingson <
b.rowlingson@lancaster.ac.uk> wrote:

> On Fri, Oct 29, 2010 at 3:57 PM, Dazhi Jiao <dazhi.jiao@gmail.com> wrote:
> > Hi, Barry,
> >
> > Thank you for the reply. Here are a few examples.
> >
> > They are registered to NAD 83 California Zone V in feet. What I want to
> map
> > to should be the most common longitude latitude system. For example,
> > 6638699, 1924377 should be projected to -117.745, 34.28
> >
> >
> > 6425591 1894450
> > 6425843 1893769
> > 6425828 1893347
>
>  Ah ha, that's more like it. I look up California in my handle table
> of EPSG codes and find:
>
> +proj=lcc +lat_1=35.46666666666667 +lat_2=34.03333333333333
> +lat_0=33.5 +lon_0=-118 +x_0=2000000.0001016 +y_0=500000.0001016001
> +ellps=GRS80 +datum=NAD83 +to_meter=0.3048006096012192 +no_defs
>
>  or epsg:2229 for short is NAD83/California Zone 5 (ftUS)
>
> So I can do:
>
> library(sp);library(rgdal)
> pts =
> data.frame(x=c(6425591,6425843,6425828,6638699),y=c(1894450,1893769,1893347,1924377))
> coordinates(pts)=~x+y
> proj4string(pts)=CRS("+init=epsg:2229")
> ptsLL = spTransform(pts,CRS("+proj=longlat +datum=WGS84"))
>
> giving:
>
> ptsLL:
>
> SpatialPoints:
>             x        y
> [1,] -118.4500 34.19720
> [2,] -118.4492 34.19533
> [3,] -118.4492 34.19417
> [4,] -117.7450 34.28000
> Coordinate Reference System (CRS) arguments: +proj=longlat +datum=WGS84
> +ellps=WGS84 +towgs84=0,0,0
>
>
> How's that?
>
> Barry
>

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