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Re: How to deal with history ocean station data
Title: Re: How to deal with history ocean station
data
Chi,
I personally would not interpolate these data onto an
xyzt grid. I think you will find that it is much too sparse and
interpolation would give users a misleading impression of the actual
amount of data that is there. What we have done with the WOD
data is put it onto a grid by averaging it in bins (for sst we use
monthly averages, 1-deg squares, and standard depths). We serve
this along with the number of observations in each bin and the
standard deviation so users can make an evaluation of the quality of
the mean. If users need data in an area where the data is very
sparse, they can then make their own judgement on whether or not
interpolation is a scientifically sound thing to do, depending on the
nature of their investigation. If users need data in a box
where there is a lot of data - they can see this by the number of
observations, they may decide to go back to the actual observations
on their own and do further subsetting. Either way, you are
providing them with real data and information rather than a
"black box" of interpolated values. Lynn
At 4:37 PM -0300 6/18/03, Chi wrote:
Hi Joe
Thanks for your information. Actually
my problem is not about the file format of world ocean
database. I 've got the world ocean view software, used it to
import the data I downloaded and export
the nitrate data into a clearly-formatted text file. All the
x/y/z/t and nitrate values are well listed in
the exported text file.
My problem is more of a strategy
problem at this stage. I know the data format, but I don't
know
which approach to choose to process the data. Should I
interpolate whole data onto XYZT structure?
I noticed that the numbers of observed data records in different
years are dramatically different, for
example, 1700 in 1980 and 70000 in 1995. Therefore does it make
sense to do the interpolation in the
x/y/z/t 4D domain? Another questions is that the areas where
nitrate was measured don't seem to cover
the global ocean.
In my assumption I'd like to make LAS work
on the dataset like this. The user can select within one of
the
areas where data was collected from the map, also he can choose
from the years when data was measured,
then he will get the interpolated data for the area and the year.
Therefore I will only need to do interpolation
in an area in one specific year. Does this idea make sense ?
Besides I don't know how to define multiple
regions in a netcdf file so the user can choose from them in the
map?
Thanks a lot, Ding
Joe McLean wrote:
Hi Ding,
Chi wrote:
Hi dear LAS users
I have the ocean station data for nitrate from
1965 to 2000, which was downloaded from NOAA world ocean database web
site at http://www.nodc.noaa.gov/OC5/SELECT/dbsearch/dbsearch.html
The nitrate data was collected in different areas
lon/lat/depth and in different years. For instance, some data was
collected in area 1 only at 1970 and 1983. And the areas ( lon/lat)
were not uniformly distributed. I don't know how to proceed on
this dataset.
The file you downloaded from NODC contains data in the OCL WOD native
format, an ascii representation of the structure and data. NODC
offers some fortran programs which will allow you to read the
data. You can read about this at http://www.nodc.noaa.gov/OC5/WOD01/doc01.html
So far my previous LAS experience
was that I did 3D interpolation on a profile dataset and managed to
make LAS work on it.
In order to interpolate the data onto a XYZT gridded structure, you
would need to extract the X,Y,Z,T, and Nitrate values from this file
first.
In the LAS developers group, we are working on providing access to
the World Ocean Database through LAS and will have more information
soon.
Anybody can give
me some suggestions or information? Any help will be
appreciated.
Thanks a lot,
Ding
--------------------------------------------
Lynn deWitt
ldewitt@pfeg.noaa.gov
Pacific Fisheries Environmental Laboratories
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
(831)-648-9036
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