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>.00.nc | ├─ 002_035TOPEX.00.nc |
| └─ <cycle>_<pass><mission>.00.nc | └─ 002_170TOPEX.00.nc |
| <cycle> | 003 |
| ├─ <cycle>_<pass><mission>.00.nc | ├─ 003_035TOPEX.00.nc |
| └─ <cycle>_<pass><mission>.00.nc | └─ 003_170TOPEX.00.nc |
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 { dimensions: n = 23 ; variables: 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.