Dear all,
I tryed both suggestions and they worked fine.
In fact, the short solution is

require(rgdal)
require(maptools)
mes01jan<-readGDAL("jan_00")
write.asciigrid(mes01jan,"mes01jan.asc")

Thanks Mike! Thanks Alex!

best wishes,

miltinho astronauta
brazil

On Fri, Sep 19, 2008 at 10:46 PM, Michael Sumner <mdsumner@utas.edu.au>wrote:

> I tried this, and AAIGrid is not available for creation by rgdal on my
> machine. See gdalDrivers() for those available.
>
> If you install FWTools you can use a workaround to convert the export
> externally, e.g.
>
> x <- readGDAL(system.file("external/test.ag", package="sp")[1])
>
> ## write to GeoTIFF
> writeGDAL(x, "mes01jan.tif",  type = "Byte")
>
> ## convert externally to AAIGrid
> system("gdal_translate mes01jan.tif mes01jan.asc -of AAIGrid -ot Byte")
>
> ## check result
> system("gdalinfo mes01jan.asc")
>
> I don't believe that AAIGrid can explicitly support type Byte without
> augmentation, so I would carefully check the coercion that occurs (if it's
> actually needed).
>
> Cheers, Mike.
>
> milton ruser wrote:
>
>> Dear all,
>> I am reading a set of maps from ArcGRID format using rgdal and I need to
>> export to ASC format.
>>
>> But when I try the commands below, I get an error.
>>
>> require(rgdal)
>>
>> mes01jan<-readGDAL("jan_00")
>> image(mes01jan, col=topo.colors(50))  #looks find
>> writeGDAL(mes01jan, "mes01jan.asc", drivername = "AAIGrid", type="Byte")
>>
>> Any idea?
>>
>> miltinho, brazil
>>
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