[R-sig-Geo] from ArcGIS GRID to .ASC

[Roger Bivand]

On Fri, 19 Sep 2008, milton ruser wrote:

> 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")

One final note: write.asciigrid() in sp has arguments:

> args(write.asciigrid)
function (x, fname, attr = 1, na.value = -9999, ...)

while its copy in maptools has:

> args(writeAsciiGrid)
function (x, fname, attr = 1, na.value = -9999, dec = options()$OutDec,
     ...)

This accommodates problems that we've seen in ArcGIS' handling of locales 
differing from users' expectations - by setting dec=, you can impose the 
understanding of other software.

Roger

>
> Thanks Mike! Thanks Alex!
>
> best wishes,
>
> miltinho astronauta
> brazil
>
> On Fri, Sep 19, 2008 at 10:46 PM, Michael Sumner <mdsumner at 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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>>
>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no