Format Description

Each data base extraction of a product contains the following four files.

Parameter Description
<mission>.nc.tar.gz Product in NetCDF format
<mission>.log Logfile of the data extraction step
README Readme file which describes the data
preview.pdf Plot of the extracted altimeter data

This file contains the extracted altimeter data in NetCDF format.
The compressed file includes a directory for each cycle and a NetCDF file for each pass.

In General Example for Product SLA
<cycle> 002
├─ <cycle>_<pass><mission> ├─
└─ <cycle>_<pass><mission> └─
<cycle> 003
├─ <cycle>_<pass><mission> ├─
└─ <cycle>_<pass><mission> └─

In general the structure of each NetCDF is the same. They differ only in the number and types of the parameters which are product depending. At first the NetCDF has an attribute dimensions which are number of altimeter points in the current file. Each parameter is stored in a variable with additional attributes such as unit, description, etc. The mission, cycle number and pass number are also stored as global attributes.

Example for Product SLA
netcdf \004_170TOPEX.00 {
     n = 23 ;
     double glon.00(n) ;
          glon.00:unit = "deg" ;
          glon.00:description = "longitude of satellite footprint" ;
     double glat.00(n) ;
          glat.00:unit = "deg" ;
          glat.00:description = "geodetic latitude of satellite footprint" ;
     double jday.00(n) ;
          jday.00:unit = "d" ;
          jday.00:description = "julian day epoch 2000.0" ;
     double sla.29(n) ;
          sla.29:unit = "m" ;
          sla.29:description = "sea level anomalies " ;
     double mssh.01(n) ;
          mssh.01:unit = "m" ;
          mssh.01:description = "mean sea surface height" ;
     double gflags.29(n) ;
          gflags.29:unit = "-" ;
          gflags.29:description = "geophysical corrections quality flags" ;
     double oflags.00(n) ;
          oflags.00:unit = "-" ;
          oflags.00:description = "Orbit status and quality flags" ;
     double iflags.00(n) ;
          iflags.00:unit = "-" ;
          iflags.00:description = "instrument status and quality flags" ;
// global attributes:
          :mission = "topex" ;
          :cycle = "004" ;
          :pass = "170" ;

This log file is created by the OpenADB system while extracting data. This file is not important for the user, but it helps admin to solve problems if they occur.

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