[R-sig-Geo] convert point and map coordinates UTM to WSG

[Marc Marí Dell'Olmo]

Dear all,

I have tried to transform coordinates from UTM Zone-31 ED-50 Spain
Portugal (EUR-D code in this web
http://earth-info.nga.mil/GandG/coordsys/onlinedatum/CountryEuropeTable.html
# EURD) to coordinates WSG84 ( google maps coordinates) with the
"ptransform" of the proj4 library and I can not do it right (first
syntax). I have tried also using the "spTransform" of the rgdal
library (second syntax) and I have not been successful.

I attach the syntax used, I got 4 points with coordinates ED ESP-50 (
"utm" in the syntax) and their respective coordinates WSG84 (wgs.gold
"in the syntax). Can anyone tell me where is the error?

Thank you very much,

Marc

> #First sintax
> library(proj4)
> x.utm <- c(428727134,431587743,434639340,426268557)
> y.utm <- c(4584118048,4581465377,4584855001,4584607449)
> x.wgs <- c(41.4036923115558,41.38010926480547,41.41148169051035,41.409534433320914)
> y.wgs <- c(2.145810127258301,2.1807003021240234,2.2183799743652344,2.1170568466186523)
>
> utm <- cbind(x.utm, y.utm)
> wgs.new <- ptransform(utm, "+proj=utm  +ellps=intl +zone=31 +towgs84=-84,-107,-120,0,0,0,0,0 +no_defs",
+                  "+proj=latlong  +datum=WGS84")
> wgs.new
          [,1]     [,2]     [,3]
[1,] -2.236353 1.570775 39.63333
[2,] -2.236353 1.570775 39.63333
[3,] -2.236353 1.570775 39.63333
[4,] -2.236353 1.570775 39.63333
> (wgs.gold <- cbind(x.wgs, y.wgs))
        x.wgs    y.wgs
[1,] 41.40369 2.145810
[2,] 41.38011 2.180700
[3,] 41.41148 2.218380
[4,] 41.40953 2.117057
>
>
>
> #Second sintax
> library(rgdal)
> (data.utm <- data.frame(x.utm,y.utm,x.wgs,y.wgs))
      x.utm      y.utm    x.wgs    y.wgs
1 428727134 4584118048 41.40369 2.145810
2 431587743 4581465377 41.38011 2.180700
3 434639340 4584855001 41.41148 2.218380
4 426268557 4584607449 41.40953 2.117057
> coordinates(data.utm) <- c("x.utm", "y.utm")
> proj4string(data.utm) <- CRS("+proj=utm  +ellps=intl +zone=31 +towgs84=-84,-107,-120,0,0,0,0,0 +no_defs")
> (wgs.new2 <- spTransform(data.utm, CRS("+proj=latlong +datum=WGS84")))
          coordinates    x.wgs    y.wgs
1 (-128.134, 89.9988) 41.40369 2.145810
2 (-128.134, 89.9988) 41.38011 2.180700
3 (-128.134, 89.9988) 41.41148 2.218380
4 (-128.134, 89.9988) 41.40953 2.117057



2009/3/23 Paul Hiemstra <p.hiemstra at geo.uu.nl>
>
> Hi,
>
> To transform coordinates you can use the spTransform function from the rgdal pacakge. It uses proj4 to do the transformations. Proj uses a string to describe a certain projection, the so called proj4string. If you can determine the proj4string for both your projections you can transform between them. The first string (WGS84) looks like this:
>
> "+proj=longlat +datum=WGS84"
>
> The second (UTM) something like:
>
> "+proj=utm +zone=yourzone +datum=yourdatum"
>
> See the documentation of spTransform for more information on how to use the function.
>
> cheers and hth,
> Paul
>
> Marc Marí Dell'Olmo wrote:
>>
>> Dear R-users,
>>
>> Can anyone tell me how to convert point coordinates from WSG84 (google
>> maps coordinates) format to UTM HUSO-31 ED-50. And if I have a map
>> (shp format) with UTM HUSO-31 ED-50 coordinates, how can I convert to
>> WSG84 (google maps coordinates) coordinates. Should I install some
>> external software?
>>
>> Can anyone tell me the instructions?
>>
>> Thank you,
>>
>> Marc
>>
>> _______________________________________________
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>> R-sig-Geo at stat.math.ethz.ch
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>>
>
>
> --
> Drs. Paul Hiemstra
> Department of Physical Geography
> Faculty of Geosciences
> University of Utrecht
> Heidelberglaan 2
> P.O. Box 80.115
> 3508 TC Utrecht
> Phone:  +3130 274 3113 Mon-Tue
> Phone:  +3130 253 5773 Wed-Fri
> http://intamap.geo.uu.nl/~paul
>