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

[Migun Shakya]

Hi Mike and Erin,
I added the projection to the shape file as suggested by Erin.

Then i plotted the rivers over and plotted my data points (places
where i collected samples). All my data points look accurate.


Thank you so much.

This was my first try working with GIS data. And, it was fun.

Migun

On Mon, Feb 25, 2013 at 9:30 PM, Michael Sumner <mdsumner at gmail.com> wrote:
> 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