[R-sig-Geo] Proj4 natgrid coordinate transformation error

[Jonas Schmedtmann]

Hi everyone,
I’m trying to use the nadgird parameter for coordinate transformation from the portuguese Hayford Gauss IGeoE system to UTM 29 WGS84 used in Landsat images for Portugal. I have the following code, which produces an error, so I wonder if I got everything right in my proj4strings. I’ve tried a lot of things, and an intensive google search did not solve my problem either. I got the file 'ptLX_e89.gsb’ from a professor of mine so I assume there’s nothing wrong with it.

> PROJ4_IGEOE<-CRS("+proj=tmerc +lat_0=39.66666666666666 +lon_0=-8.131906111111112 +k=1 +x_0=200000 +y_0=300000 +ellps=intl +units=m +nadgrids=ptLX_e89.gsb +wktext +no_defs")
> PROJ4_UTM<-CRS("+proj=utm +zone=29 +ellps=WGS84 +datum=WGS84 +units=m")
> area<-readShapePoly("../01 Dados/02 Dados espaciais/AREA_ESTUDO", proj4string=PROJ4_IGEOE)
> area_wgs84<-spTransform(area, PROJ4_UTM)
Error in .spTransform_Polygon(input[[i]], to_args = to_args, from_args = from_args,  : 
  error in pj_transform: failed to load datum shift file
> 

I’d appreciate any help. Thanks in advance!
Jonas Schmedtmann