[gdal-dev] Writing a Tiff

[Henning Bredel]

On Mon, 2009-01-19 at 20:57 +1100, Michael Sumner wrote:
> Hello,
> 

Hey Mike,

thanks for your exhaustive answere :-)

> Note this recent R-Sig-Geo post about the "in-development" nature of the 
> latest builds of rgdal - you need to let us know what versions you are 
> using. Also, view the definition of writeGDAL() to see how the lower 
> level functions are used.
> 
> https://stat.ethz.ch/pipermail/r-sig-geo/2009-January/004830.html
> 

I have read that message, but my version is not affected be the one
Roger refers to:

,----------------------------------
> library(rgdal)
Loading required package: sp
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 1.5.2, released 2008/05/29
GDAL_DATA: /usr/local/lib/R/site-library/rgdal/gdal
Loaded PROJ.4 runtime: Rel. 4.6.0, 21 Dec 2007
PROJ_LIB: /usr/local/lib/R/site-library/rgdal/proj
> sessionInfo()
R version 2.7.1 (2008-06-23) 
i486-pc-linux-gnu 

locale:
LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;\
LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;\
LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;\
LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods
base     

other attached packages:
[1] rgdal_0.5-33 sp_0.9-29   

loaded via a namespace (and not attached):
[1] grid_2.7.1      lattice_0.17-20
`----------------------------------

> BTW, you can simplify the writing of GTiffs with writeGDAL() -unless you 
> are intending to develop your function to write to the file in smaller 
> pieces. The code to do that can be as simple as this:


> library(rgdal)
> ## read in matrix to bm
> ## . . .
> ## generate X/Y coordinates - assuming your matrix is aligned as image() 
> expects (replace 0 and 1 as needed)
> xx <- seq(0, length = nrow(bm), by = 1)
> yy <- seq(0, length = ncol(bm), by = 1)
> ##
> writeGDAL(image2Grid(list(x = xx, y = yy, z = bm))
> 

That snipped brought my machine »to its knees« .. but that is
a problem of R itself (actually, I'm currently exploring).

> 
> But, your R function works for me for the following simple test. As 
> Frank mentioned, it probably comes down to a version problem or a file 
> size limit (although that seems unlikely since your input matrix "bm" 
> must be completely loaded in memory).
> 
>  library(rgdal)
> #Loading required package: sp
> #Geospatial Data Abstraction Library extensions to R successfully loaded
> #Loaded GDAL runtime: GDAL 1.6.0, released 2008/12/04
> #Path to GDAL shared files: C:\inst\R\library/rgdal/gdal
> #Loaded PROJ.4 runtime: Rel. 4.6.1, 21 August 2008
> #Path to PROJ.4 shared files: C:\inst\R\library/rgdal/proj
> 
> data(volcano)  # matrix 87x61
> bm.writeTiff(volcano, "volc.tif")
> #         used (Mb) gc trigger (Mb) max used (Mb)
> #Ncells 305831  8.2     597831   16   407500 10.9
> #Vcells 149194  1.2     786432    6   467409  3.6
> tst <- readGDAL("volc.tif")
> 
> #volc.tif has GDAL driver ltalk X6
> #and has 87 rows and 61 columns
> 

My image got dimension 8950 9790    7, could that dimension
be the problem?

Regards

  Henning

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