Hi Manuel, > I have to select and export oceanographic data from a netCDF file depending > on time slices. > I am using the netCDF4 library together with numpy, scipy and gdal. > So far I can already read the parts of the nc file (dimensions, variables, > attributes). > > Now my questions: > > 1) How can I access the "water surface elevation" variable values for a > certain time slice? > I don't really understand the principle, because if I print the variable I > get all values, of course. > So, may I have to join the time to the elevation values at first? I don't > know how the records are assigned to the time values. Sorry, we can answer such a question for the C, Java, C++, or Fortran interfaces, but all the Python APIs for netCDF are developed and supported elsewhere, and they have different APIs. For example, if you're using Jeff Whitaker's netCDF-4 module for python: http://code.google.com/p/netcdf4-python/, you should contact him for answers to questions about his API. > 2) What kind of data type should I use? (multidimensional array, ... because > the file has >7GB) I expect you'd want a 2D array for "water surface elevation" at a specified time. It should be possible to read in each time slice separately into such a 2D array. > 3) I want to use GDAL for generating a Shapefile out of the selected time > slices. Is it better to cache the selected data (to ASCII file, ...) or doing > a direct shp creation? Considering the read/write performance. Sorry, we didn't develop and don't support the GDAL library either, so I can't answer that question. --Russ > Here's a part of the file structure: > ---------------------------------------- > dimensions: > time = unlimited (49 currently) > zip2 = 1076093 > > variables: > double time(time) > time:long_name = "coordinate variables of time" > time:units = "seconds since 2010-08-09" > > float e (time,zip2) > e:long_name = "water surface elevation from still water level" > e:units = "meter" > e:figure = "scalar" Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: VMR-409919 Department: Support netCDF Priority: Normal Status: Closed
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