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Re: [ferret_users] Re: handling data



Hi all,
Golla Nageswararao wrote about a dataset which is a big collection of profile data at a set of global locations and sampled over depths.

We had taken this discussion off-line and found a way to sample the dataset so there is a collection only of the Indian Ocean data.  However the question remains of what to do with a set of scattered XY locations, each with a profile that does not contain the same set of depths.   There seems to be more and more of this kind of data that people are trying to work with.  It is not gridded data and it doesn't necessarily make sense to try to interpolate it onto a grid.

The CF standard for netCDF datasets has added some sections on organizing such data collections under the heading Discrete Sampling Geometries, including collections of time series, collections of profiles, and so forth. Please see Chapter 9 of the documentation,

http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#discrete-sampling-geometries

and the examples, shown in Appendix H of the same document
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#appendix-examples-discrete-geometries

We have upcoming projects in Ferret and LAS development to work with this sort of data. We'll want to write these kinds of Discrete Geometries files Ferret, and to come up with some tools to work with them.  This will include ways to subsample sets of profiles or time series from a big collection, and new ways to visualize this kind of data.

As always we encourage contributions of Ferret scripts, Python tools that might be incorporated using PyFerret, and also general ideas for handling this sort of data. So if you're thinking about non-gridded data, please lend your ideas.


Ansley



On 4/17/2013 4:36 AM, golla nageswararao wrote:
Hi all,
I could solve this problem to some extent by doing gaussian interpolation technique
I used scat2gridgauss_xy function to map the data on profile number and depths.
But now the problem is data size.
I going to get dimension size of 202670x293.
I tried to split the data also, it is giving the following error.
**ERROR in efcn_compute() allocating 475058480 bytes of memory
    work array 3:  X=1:202670, Y=1:293, Z=1:1, T=1:1, E=1:1, F=1:1
 **ERROR: error in external function
The only way to decrease the data size is to extract the data for Indian Ocean domain (original is world oceans)
Can anybody suggest me how to extract for my domain interest (data set is also having longitude and latitude as variables), and compress the data into the reasonable size.
Thanks in advance




On Tue, Apr 16, 2013 at 8:59 PM, golla nageswararao <ezeenag4u@xxxxxxxxx> wrote:
Hi all,

I am having a dataset with variables depth, latitude, longitude, temp, salt in only one dimension (i.e., i=1:2600000). Actually the data consists of profiles at different locations.
i=1 z=0 temp1 salt1 lat1 lon1
i=2 z=20 temp1 salt1 lat1 lon1
i=3 z=50 temp1 salt1 lat1 lon1
i=4 z=100 temp1 salt1 lat1 lon1
i=5 z=250 temp1 salt1 lat1 lon1
i=6 z=0 temp2 salt2 lat2 lon2
i=7 z=15 temp2 salt2 lat2 lon2
i=8 z=25 temp2 salt2 lat2 lon2
i=9 z=45 temp2 salt2 lat2 lon2
i=10 z=65 temp2 salt2 lat2 lon2
.
.
.
.
How to handle this type of data? I want to extract profiles in Indian Ocean. I tried to do with "if" command. But the program is coming out of ferret after i=53. I dont know whats the problem. Can anybody help me in this regard.

Thanks in advance.

--
With Best regards,
G.NageswaraRao,



--
With Best regards,
G.NageswaraRao,


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