[R-sig-Geo] Converting State Plane Coordinates

[Dan Putler]

Roger,

This won't really matter since they are very close, but given the data 
source and a North America based company, my guess is the underlying 
datum is NAD83.

Dan

On 08/24/2010 10:45 AM, Roger Bivand wrote:
> 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 écrit :
>>      
>>> 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 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
>>>>> _______________________________________________
>>>>> R-sig-Geo mailing list
>>>>> R-sig-Geo at stat.math.ethz.ch
>>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>>
>>>>>            
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>>>
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>