[R-sig-Geo] Automatic geographical projection parameters setting

[Pascal Oettli]

Hello,

Please reply to the list, not only to me.

Example taken from rgdal::spTransform:


 > crds <- matrix(data=c(9.05, 48.52), ncol=2)
 > spPoint <- SpatialPoints(coords=crds,
+                          proj4string=CRS("+proj=longlat +ellps=sphere 
+no_defs"))
 > a <- spTransform(spPoint, CRS(paste("+proj=ob_tran +o_proj=longlat",
+                                     "+o_lon_p=-162 +o_lat_p=39.25 
+lon_0=180 +ellps=sphere +no_defs")), use_ob_tran=TRUE)
 > a
SpatialPoints:
      coords.x1 coords.x2
[1,] -5.917698  -1.87195
Coordinate Reference System (CRS) arguments: +proj=ob_tran 
+o_proj=longlat +o_lon_p=-162 +o_lat_p=39.25 +lon_0=180 +ellps=sphere
+no_defs
 >
 > lon_0 <- 180
 > o_lon_p <- -162
 > o_lat_p <- 39.25
 >
 > crs.args <- paste("+o_lon_p=",o_lon_p," +o_lat_p=",o_lat_p," 
+lon_0=",lon_0," +ellps=sphere +no_defs", sep='')
 > b <- spTransform(spPoint, CRS(paste("+proj=ob_tran 
+o_proj=longlat",crs.args)), use_ob_tran=TRUE)
 > b
SpatialPoints:
      coords.x1 coords.x2
[1,] -5.917698  -1.87195
Coordinate Reference System (CRS) arguments: +proj=ob_tran 
+o_proj=longlat +o_lon_p=-162 +o_lat_p=39.25 +lon_0=180 +ellps=sphere
+no_defs


Regards,
Pascal


On 05/29/2013 06:26 PM, Francesco Carotenuto wrote:
> Thank you for the reply but in my post I've already explained that the
> function doesn't "read" any object.
>
> ------------------------------------------------------------------------
> *Da:* Pascal Oettli <kridox at ymail.com>
> *A:* Francesco Carotenuto <carotenuto_francesco at yahoo.it>
> *Cc:* "r-sig-geo at r-project.org" <r-sig-geo at r-project.org>
> *Inviato:* Mercoledì 29 Maggio 2013 10:15
> *Oggetto:* Re: [R-sig-Geo] Automatic geographical projection parameters
> setting
>
> Hello,
>
> Something like that?
>
>  > LONG <- 20
>  > LAT <- 5
>
>  > crs.args <- paste("+proj=laea +lat_0=",LAT," +lon_0=",LONG," +x_0=0
> +y_0=0 +ellps=WGS84 +units=m +no_defs",sep="")
>
>  > CRS("+proj=laea +lat_0=5 +lon_0=20 +x_0=0 +y_0=0 +ellps=WGS84
> +units=m +no_defs")
> CRS arguments:
>    +proj=laea +lat_0=5 +lon_0=20 +x_0=0 +y_0=0 +ellps=WGS84 +units=m
> +no_defs
>
>  > CRS(crs.args)
> CRS arguments:
>    +proj=laea +lat_0=5 +lon_0=20 +x_0=0 +y_0=0 +ellps=WGS84 +units=m
> +no_defs
>
> Regards,
> Pascal
>
>
> On 05/29/2013 04:58 PM, Francesco Carotenuto wrote:
>  > Hi
>  > to all,
>  > I
>  > need to automatically set the geographical coordinates of the
> projection’s
>  > centre to project different polygons in different territories. My
> problem is the
>  > following.
>  > By
>  > using spTransform(xy, CRS("+proj=laea +lat_0=LAT +lon_0=LONG +x_0=0
> +y_0=0
>  > +ellps=WGS84 +units=m +no_defs")),  I would like to set  +lat_0 and
> +long_0 as objects (here “LAT” and
>  > “LONG”) that I automatically generated. Unfortunately, this function
> doesn’t
>  > read objects (even if “as.numeric”) but only numerical values set
> manually. Is
>  > there a way to set these coordinates as objects?
>  > Many
>  > thanks.
>  >     [[alternative HTML version deleted]]
>  >
>  >
>  >
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>