[R-sig-Geo] projection string when using asSGDF_GROD()

[Harry Kim]

Hi Paul,

     Thank you so much for the prompt response. Here is the actual code I ran:

library(rgdal)
dpath<-"./glwd_3/hdr.adf"
x <- new("GDALReadOnlyDataset", dpath)
getDriver(x)
getDriverLongName(getDriver(x))

wetland<-asSGDF_GROD(x, offset=c(3600,20400), region.dim=c(8140,
18000),CRS("+proj=longlat" ))

save(wetland,file="wetland.Rdata" )

If I run this code without the CRS() argument for p4s, I can read in
the data without any errors--but it doesn't project correctly. It's
very strange that it doesn't inherit the projection (lat and long)
from the original raster image.

traceback() produces the following:

 > traceback()
5: getRasterData(x, offset = offset, region.dim = region.dim,
output.dim = output.dim,
       ...)
4: asSGDF_GROD(x, offset = c(3600, 20400), region.dim = c(8140,
       18000), CRS("+proj=longlat"))
3: eval.with.vis(expr, envir, enclos)
2: eval.with.vis(ei, envir)
1: source("wetland.R")

Thank you so much in advance!
Harry




On Mon, Dec 8, 2008 at 1:26 PM, Paul Hiemstra <p.hiemstra at geo.uu.nl> wrote:
> Hi Harry,
>
> Without the output of traceback() to show what exactly went wrong in what
> function it is hard to say what is wrong. A small piece of sample code
> reproducing the error would also make this diagnosis much easier.
>
> good luck and cheers,
> Paul
>
> Harry Kim wrote:
>>
>> Dear r-sig-geoers,
>>
>>      I need some help reading in a raster data and at the same time
>> project it so I can use the overlay() function. The data I am reading
>> in is quite big, so I managed to source in the subset of the data by
>> running:
>>
>>      wetland= asSGDF_GROD(x, offset=c(3600,20400),
>> region.dim=c(8140,18000))
>>
>>      Running summary(wetland) gives:
>>
>>      Object of class SpatialGridDataFrame
>> Coordinates:
>>        min      max
>> x -9.999992 140.0000
>> y -7.833337  60.0000
>> Is projected: NA
>> proj4string : [NA]
>> Number of points: 2
>> Grid attributes:
>>  cellcentre.offset    cellsize cells.dim
>> x         -9.995825 0.008333334     18000
>> y         -7.829171 0.008333334      8140
>> Data attributes:
>>        Min.      1st Qu.       Median         Mean      3rd Qu.
>> Max.
>> 1.000000e+00 3.000000e+00 4.000000e+00 5.594000e+00 9.000000e+00
>> 1.200000e+01
>>        NA's
>> 1.396304e+08
>>
>> ----------------------------------------------------------------------------------------------------------------------------------
>>
>> The original data is geocoded in latitude and longitude spanning from
>> -180 to 180 for longitude and from -90 to 90 for latitude. As you
>> probably noticed, the read-in raster image does not inherit the
>> projection.
>> I tried to project the data by running:
>>
>> asSGDF_GROD(x, offset=c(3600,20400),
>> region.dim=c(8140,18000),CRS("+proj=longlat" ))
>>
>> and I get a message that says
>>
>> Error: object is not subsettable
>>
>> If anybody could help me out, I would greatly appreciate it.
>>
>> Thank you
>> Harry
>>
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>>
>
>