Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
On 10/18/12 8:32 AM, "Alexander Belousov" <mynewsmailbox at gmx.de> wrote:
>Dear all,
>
>I am trying to project my LongLat-maps to a plane.
>The ultimate purpose is to do a search of points in vicinity of other
>points using overlay-commands (sp) with radius in km.
>
>I am applying spTransform (package rgdal) and it gives my some curious
>results.
>
>An example.
>Let's take a point lying somewhere in Germany, zone=32U
>
>x <- 8.968735
>y <- 49.454735
>
>After conversion I sould get something like
>
>Easting: 426858 (km)
>Northing: 5427937 (km)
>
>sp1 <- SpatialPoints(matrix(c(x,y), ncol=2), proj4string =
>CRS("+proj=longlat +datum=WGS84"))
>
>sp1Transformed <- spTransform(sp1, CRS("+proj=merc +zone=32u
>+datum=WGS84"))
>coordinates(sp1Transformed)
>
> coords.x1 coords.x2
>[1,] 998395.0133 6319888.068
>
>The result is an obvious nonsense.
>
>Well, after some deliberation I swapped the original coordinate columns:
>
>x <- 49.454735
>y <- 8.968735
>
>sp2 <- SpatialPoints(matrix(c(x,y), ncol=2), proj4string =
>CRS("+proj=longlat +datum=WGS84"))
>
>sp2Transformed <- spTransform(sp2, CRS("+proj=merc +zone=32u
>+datum=WGS84"))
>coordinates(sp2Transformed)
>
> coords.x1 coords.x2
>[1,] 5505275.918 995840.692
>
>Now the northing (which comes first after swapping) looks better, at
>least it falls within Germany, which is however not to say about the
>easting.
>
>Apparently I am missing an important point by the transformation.
>Any help will be greatly appreciated!
>
>Regards
>
>Alex
>
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