[R-sig-Geo] display location on google earth

[Felipe Carrillo]

Thanks for the advice, it is working now. 
 

    On Thursday, December 29, 2016 10:19 AM, Barry Rowlingson <b.rowlingson at lancaster.ac.uk> wrote:
 
 

 You made a couple of little mistakes! See below:

On Thu, Dec 29, 2016 at 5:51 PM, Felipe Carrillo via R-sig-Geo
<r-sig-geo at r-project.org> wrote:
> Hi;I have a shapefile named 'Wolf' that I can display in google with the following code:  # Show the shapefile on top of google
>  writeOGR(Wolf, "Wolf.kml", "Wolf", driver="KML")
>  system("open Wolf.kml")
>
> However, I am having problems with a single set of coordinates that I would like to use to display a location.Could someone show me how to display on google with the following coordinates?
>  Latitude 38°34'02",  Longitude 121°23'14"  NAD27
> I have tried:
>  require(rgdal)
>  library(sp)

You've defined lat and lon here as characters - these should be numeric:

> lat <- '38.34477586'
>  lon <- '-121.23387625'

  lon <- -121.23387625
  lat <- 38.34477586


>  # make a data frame
>  coords <- as.data.frame(cbind(lon=lon,lat=lat))
>  coords
>  # make it a spatial object
>  coordinates(coords) <- ~lat+lon

Here you've got your lat-lon the wrong way round. coordinate
assignment wants lon first, so:

coordinates(coords)=~lon+lat

>  coords <- spTransform(coords)
>
> But I am getting the following error:
> Error in (function (classes, fdef, mtable)  :
>  unable to find an inherited method for function ‘spTransform’ for signature ‘"CRS", "missing"’

That error is because you've tried to transform something without giving a CRS.

You seem to have lat-long in NAD27 datum, which I think is EPSG code
4267. So first give it that code:

proj4string(coords)=CRS("+init=epsg:4267")

and now you can convert to whatever you want:

 spTransform(coords, "+init=epsg:4326")

SpatialPoints:
        lon      lat
1 -121.2349 38.34469
Coordinate Reference System (CRS) arguments: +init=epsg:4326
+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0

Which seems to concur with this converter tool:

http://tagis.dep.wv.gov/convert/

which returns:

38.344689,-121.234935

but I'm no expert when it comes to datum shifts in CRS transformations...

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