[Gdal-dev] IPCC raster format

[Tim Sutton]

Hi

I wrote a tool in c++ once to read this and if I recall correctly  
spit out arc/info ascii grid files. Its been a while since I looked  
at it so Ill need to dig it up and recheck exactly what it did. Pete  
can you remember if this is in the climate data processing wizard? I  
have no network access as I write this so I will only be able to  
confirm for you tomorrow what I actually have. Ivan if you still   
have not found a suitable solution and Ill dig out what I have.

Regards

Tim

On 16/06/2006, at 12:08, Ivan Lucena wrote:

> Hi there,
>
>
>
> I would rather been watching the World Cup, but I have to get this  
> data in a usable format and there is no better place to get it than  
> from GDAL’s experts.
>
>
>
> The “Intergovernmental Panel on Climate Change” (IPCC) offers data  
> on the web in a format described by this Fortran source code: (The  
> file extension is just a generic “.dat”)
>
>
>
> http://ipcc-ddc.cru.uea.ac.uk/obs/observed_fileformat.html
>
>
>
> > more cpre0130.dat
>
>     grd_sz      xmin      ymin      xmax      ymax    n_cols     
> n_rows  n_months
>
>       0.50      0.25    -89.75    359.75     89.75       720        
> 360        12
>
> …
>
> -9999-9999-9999-9999-9999-9999-9999-9999-9999   52   88  103   91    
> 65   45   27   32 …
>
> -9999-9999-9999-9999-9999   11   20   22   25   27   26   27   28    
> 31   29   28   30 …
>
> …
>
>
>
> It’s not hard to analyze the pattern on the data or the code, so I  
> figured that:
>
>
>
> - It’s an ASCII format;
>
> - There are two lines of reader (easy to read)
>
> - Each cell is 5 characters wide;
>
> - The no-data is “-9999”;
>
> - There is no separator between cells (what makes my task difficult);
>
> - It’s a multi-band raster dataset with 12 bands; (720x360x12 cells)
>
> - I am not sure if positive values can go beyond 9999 (that reminds  
> me COBOL)
>
>
>
> I am heading in the direction of writing a Python+GDAL script to do  
> the task, but I am stuck in how to separate the cells. The Fortran  
> code is doing it in just one command as you can see in the code. I  
> am thing that maybe by using the NumPY stuff embedded in GDAL I  
> could do the same.
>
>
>
> Any Idea? Any experience with this data format?
>
>
>
> Thanks in advance,
>
>
>
> Ivan
>
>
>
> -------------------------------------------------------
>
> This is a Python command line interaction with the data:
>
>
>
> >>> import gdal
>
> >>> f = open('C:/Data/IPCC/cpre0130.dat', 'r');
>
> >>> f.readline()
>
> '    grd_sz      xmin      ymin      xmax      ymax    n_cols     
> n_rows  n_months\n'
>
> >>> f.readline()
>
> '      0.50      0.25    -89.75    359.75     89.75       720        
> 360        12\n'
>
> >>> f.readline()
>
> '-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-999 
> 9-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-999 
> 9-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-9999-999 
> 9-9999-9999-9999-9999-9999-9999-9
>
>
>
> -------------------------------------------------------
>
> Fortran source code:
>
>
> program rd_ascii
> !
> ! f90 program to read in an integer ascii grid with
> ! variable dimensions into a global grid (720x360x12)
> !
>   parameter :: n_cols=720
>   parameter :: n_rows=360
>   integer, dimension (n_cols,n_rows,12) :: grid
>   character(len=72) :: infl
>   character(len=20) :: fmt
> !
>   call getarg(1,infl)
> !
>   if(infl.eq.' ')then
>     write(*,*) 'Enter ascii grid file name'
>     read(*,'(a72)')infl
>   end if
> !
>   open(1,file=infl,status='old')
>   read(1,*)
>   read(1,*)xmin,ymin,xmax,ymax,ncols,nrows,nmonths,missing
>   grid=missing
>   fmt='( i5)'
>   write(fmt(2:4),'(i3)')n_cols
>   do im=1,nmonths
>     do lat=1,n_rows
>       read(1,fmt)(grid(lon,lat,im),lon=1,n_cols)
>     enddo
>   enddo
> !
> end program rd_ascii
>
>
>
>
>
>
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Tim Sutton
tim at linfiniti.com



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