[R-sig-Geo] converting from NAD83 datum to lat,lon

[Michael Sumner]

Since you can install rgdal it would be best to go that way (I had
completely missed that you obviously had access to rgdal::spTransform,
please provide the code you are using as asked by the mailing list
guidelines).

library(rgdal)


See ?readOGR

You need a layer name, which can just be the file name without extension:

nc.river<-readOGR("~/hydromaj/hydromaj_arc.shp", "hydromaj_arc")

Then do

proj4string(nc.river)

to see that it's not NA before proceeding with spTransform.

(Re-projecting is not straightforward and you should really be
checking carefully at every step against the needs of your project, we
can't advise past the basics of just running code. )

Cheers, Mike.

On Tue, Feb 26, 2013 at 1:14 PM, Migun Shakya <microbeatic at gmail.com> wrote:
> Hi Mike,
>
> I tried the rgdal:readOGR, but got an error.
>
>> nc.river<-readOGR("~/hydromaj/hydromaj_arc.shp")
> Error in readOGR("~/hydromaj/hydromaj_arc.shp") :
>   missing layer
>
> Sorry, I am not very familiar with the data structure, but i am
> looking at the spatialreference.org. Lets see what i get.
>
> Thanks,
> Migun
>
> Here is the .prj file content for hydromaj_arc.prj
>
> PROJCS["NAD_1983_StatePlane_North_Carolina_FIPS_3200",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",609601.22],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-79.0],PARAMETER["Standard_Parallel_1",34.33333333333334],PARAMETER["Standard_Parallel_2",36.16666666666666],PARAMETER["Latitude_Of_Origin",33.75],UNIT["Meter",1.0]]
>
> On Mon, Feb 25, 2013 at 9:01 PM, Michael Sumner <mdsumner at gmail.com> wrote:
>> You need an input projection on the data, it doesn't know what you are
>> transforming FROM.
>>
>> Did you read this with maptools::readShapePoly? Try with rgdal:readOGR
>> so you get the projection automatically with the object.
>>
>> I cannot download the data from the link you provide, but if you post
>> the text of the .prj files here someone will be able to give you R
>> code to set it without re-reading.  (Explore for yourself on
>> spatialreference.org).
>>
>> Also, "lat,lon" requires a datum like any map projection - you'll need
>> to find out if you should stay with NAD83 or convert to WGS84 as in
>> Erin's code.
>>
>> Cheers, Mike.
>>
>>
>>
>> On Tue, Feb 26, 2013 at 12:45 PM, Migun Shakya <microbeatic at gmail.com> wrote:
>>> Hi Erin,
>>> I tried that but ended up getting this error. Does the spTransform
>>> function requires the data to be as data.frame?
>>> Here is what i did to read the data
>>>
>>> library(maptools)
>>> library(rgdal)
>>> nc.river<-readShapeSpatial("~/hydromaj/hydromaj_arc.shp") #reading the
>>> shape file
>>>
>>> nc1.wgs84 <- spTransform(nc.river,CRS("+proj=longlat +datum=WGS84"))
>>> Error in spTransform(xSP, CRSobj, ...) :
>>>   No transformation possible from NA reference system
>>>
>>>
>>> Thanks again
>>> Migee
>>>
>>> On Mon, Feb 25, 2013 at 5:47 PM, Hodgess, Erin <HodgessE at uhd.edu> wrote:
>>>> Hi!
>>>>
>>>> Suppose your data set is called nc1.df.
>>>>
>>>> Then you can do:
>>>> library(rgdal)
>>>> nc1.wgs84 <- spTransform(nc1.df,CRS("+proj=longlat +datum=WGS84"))
>>>>
>>>>
>>>> ________________________________________
>>>> From: r-sig-geo-bounces at r-project.org [r-sig-geo-bounces at r-project.org] on behalf of Migun Shakya [microbeatic at gmail.com]
>>>> Sent: Monday, February 25, 2013 4:21 PM
>>>> To: r-sig-geo at r-project.org
>>>> Subject: [R-sig-Geo] converting from NAD83 datum to lat,lon
>>>>
>>>> Hi all,
>>>>
>>>> Is there a way/package/trick to convert the NAD83 formatted file to
>>>> lat lon format?
>>>>
>>>> I downloaded the "Major Hydrography" dataset from NC,USA to plot
>>>> rivers into a NC map. However, the dataset is in NAD83 or in state
>>>> plane projection, but i need it to be in lat/lon.
>>>>
>>>>
>>>> Any help would be great.
>>>>
>>>>
>>>> Thanks
>>>> Migee
>>>>
>>>>
>>>> dataset can be found in:
>>>> http://data.nconemap.com/geoportal/catalog/search/resource/details.page?uuid=%7B2515713B-2CA0-476F-863F-61441A9D6F70%7D
>>>>
>>>>
>>>> The downloaded dataset consist of
>>>> hydromaj_arc.dbf
>>>> hydromaj_arc.prj
>>>> hydromaj_arc.shp
>>>> hydromaj_arc.shx
>>>> hydromaj_arc.txt
>>>> hydromaj_poly.dbf
>>>> hydromaj_poly.prj
>>>> hydromaj_poly.shp
>>>> hydromaj_poly.shx
>>>>
>>>> _______________________________________________
>>>> R-sig-Geo mailing list
>>>> R-sig-Geo at r-project.org
>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>
>>> _______________________________________________
>>> R-sig-Geo mailing list
>>> R-sig-Geo at r-project.org
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>>
>>
>> --
>> Michael Sumner
>> Hobart, Australia
>> e-mail: mdsumner at gmail.com



-- 
Michael Sumner
Hobart, Australia
e-mail: mdsumner at gmail.com