| Re: landscan data [message #46948] |
Mon, 16 January 2006 08:01  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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matthias.demuzere@geo.kuleuven.be writes:
> Well, if i try this, I always get following error message:
>
> Unable to allocate memory: to make array.
>
> Is this because the array is to large to read in at once?
Humm. Well, it's a big array, that's for sure. But
my middling machine can handle it. Do you have a
first born son? Would you be willing to trade him
to your system administrator for more process space?
If you are going to work with big data, you pretty
much have to have decent tools, or things get
hopeless quickly.
> And if so,
> what would be a proper way then to read it in??
I guess you could try reading the data in smaller
chunks, but what is the point? Eventually, you
are going to want to do something with the data
and it doesn't appear you have the memory to do it.
I think I would be thinking about getting more memory
(which is cheap) rather than thinking about complicated
workarounds.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: landscan data [message #46954 is a reply to message #46949] |
Sun, 15 January 2006 08:06  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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matthias.demuzere@geo.kuleuven.be writes:
> Is there anyone that has experience in reading the Landscan data in
> IDL? The LandScanTM Dataset comprises a worldwide population database
> compiled on a 30" X 30" latitude/longitude grid. The LandScan Dataset
> files are available in an ESRI raster binary format.
>
> Now I have all the data, but I really don=B4t succeed in reading in this
> dataset. The data includes also a header file with the following
> information:
>
> ncols 43200
> nrows 20880
> xllcorner -180
> yllcorner -90
> cellsize 0.00833333333333
> NODATA_value -9999
> byteorder LSBFIRST
I presume you tried something like this. What happened?
OpenR, lun, 'yourfile.dat', /Get_Lun, /Swap_If_Big_Endian
image = IntArr(43200L, 2088L)
ReadU, lun, image
Free_Lun, lun
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: landscan data [message #47038 is a reply to message #46948] |
Tue, 17 January 2006 03:01 |
matthias.demuzere
Messages: 32
Registered: January 2006
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Member |
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Thanks for the reply David.
I tried again to read in the whole dataset with 43200x20880 fields on
another PC, but that didn't work either. So I probably have to look to
see if I can expand my memory capacity....
Cheers,
Matthias
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