Changes between Version 1 and Version 2 of ADAGUC


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Timestamp:
Aug 22, 2008, 3:02:50 AM (16 years ago)
Author:
maartenplieger
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  • ADAGUC

    v1 v2  
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    44== The file structure ==
    5 The ADAGUC internal file structure contains variables which can be subdivided in three types: variables to store the metadata, variables to store the dimension scales and variables to store the data. A schematic overview of the ADAGUC file structure for the different types is given in the figure below. The three types of variables (metadata, dimension scales and data) are indicated with A, B and C respectively.
    6  [[Image(ADAGUC_raster_file_structure_small.jpg, 120px)]]
     5The ADAGUC internal file structure contains variables which can be subdivided in three types: variables to store the metadata, variables to store the dimension scales and variables to store the data. A schematic overview of the ADAGUC file structure for the different types is given in the figure of the file structure (below). The three types of variables (metadata, dimension scales and data) are indicated with A, B and C respectively.
     6
    77
    88''' (A) Metadata ''' - Metadata is stored in attributes which are assigned to a variable. The variables ‘product’, ‘iso_dataset’ and ‘projection’ are used to store the metadata.
    99
    10 ''' (B) Dimension scales ''' - Dimension scales are used as coordinate variables and time intervals. They provide information about geolocation and time to the data variables. The dimension scales follow the  [http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.2/ NetCDF Climate and Forecast (CF) Metadata Conventions]. Dimension scales are lists containing coordinates or time intervals. The figure below shows geographic raster data with the dimensions time, lat and lon. Its size is, in this example, 4x6x12. This means that there are 4 indexes for time, 6 for latitude and 12 for longitude. According to the CF conventions the dimensions should have the order time, lat, lon.
    11  [[Image(ADAGUC_NetCDF_dimension_scales.jpg, 120px)]]
     10''' (B) Dimension scales ''' - Dimension scales are used as coordinate variables and time intervals. They provide information about geolocation and time to the data variables. The dimension scales follow the  [http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.2/ NetCDF Climate and Forecast (CF) Metadata Conventions]. Dimension scales are lists containing coordinates or time intervals. The dimension scale figure shows geographic raster data with the dimensions time, lat and lon. Its size is, in this example, 4x6x12. This means that there are 4 indexes for time, 6 for latitude and 12 for longitude. According to the CF conventions the dimensions should have the order time, lat, lon.
    1211In case the raster data uses a geographic coordinate system, the required dimensions are time, lat and lon which represent the center of the pixel. When the raster data is projected the dimension scales x and y are included which represent the projected coordinates. The dimension scales lat and lon become a function of y and x (see the right part of the file structure), providing the latitude and longitude at the location of y and x, respectively. In this case y and x contain the projected coordinates, while lat and lon represent the geographic latitudes and longitudes in degrees at location y, x. For detailed information see the [http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.2/ CF Conventions].
    1312
    … …  
    1615The ADAGUC format currently supports X, Y and time dimensions, stored as dimension scales in the file according the CF Conventions. The driver supports two ways of time sub-setting. The first is by making selections in time by choosing band numbers, the second is by providing the time in the file name. By using gdalinfo on the ADAGUC file the available band numbers and dimensions are listed. With this information a subset can be read with for example:
    1716gdalinfo ADAGUC:thefile.nc:variable:time=20
     17 [[Image(ADAGUC_raster_file_structure_small.jpg, 250)]] [[Image(ADAGUC_NetCDF_dimension_scales.jpg, 310)]]
     18      Left: filestructure; Right: dimension scales
    1819
    1920== GDAL Creation options ==