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5.2. Basic Radar Altimetry Toolbox

The Basic Radar Altimetry Toolbox is a tool designed to use radar altimetry data. It is able:

  • to read all altimetry data from official data centres, from ERS-1 and 2, Topex/Poseidon, Geosat Follow-on, Jason-1, Envisat, Jason-2 and Cryosat, from Sensor Geophysical Data Record to gridded merged data
  • to do some processing and computations
  • to visualise the results

It is available for Windows XP, Mac OS X 10.4 and 10.5 (ppc/intel), Linux Redhat EL4.

The Basic Radar Altimetry Toolbox is a joint project between ESA and CNES.

March 2012 : update of BRAT v3
some improvements have been added to BRAT:
- Addition of an "aliases" capability, that enables users to use the same names for the most frequent data fields. The call to the geostrophic velocity algorithms is modified to use those aliases for longitude and latitude, to make things simpler for users.
- Addition of an index (brat_index_data) for data with a "time" dimension (i.e. not available for some data, like grids).
- Addition of filters algorithms (four different filters have been implemented), working along-track or on grids.
- Updated CODA to version 2.3.1.
- Internal (CODA) product type names for ERS product types have been aligned with ESA naming convention (OPR_pass_file -> ALT.OPR, WAP -> ALT.WAP)
- Updated CryoSat product format (codadef)

The current version of the Basic Radar Altimetry Toolbox is v3.1.0
See version change Logs

If you are using it, please signal us any problems and questions, and send us suggestions to improve. To report any bug or problem with the software, please use the

The Basic Radar Altimetry Toolbox can be divided in four main components:

  1. Data reading (also called "ingestion")
  2. Processing routine functions
  3. Visualisation functions
  4. Graphic User Interface (GUI)

The structure is onionskin: each layer using the previous ones, and being available to be used without the ones above (e.g. you use the processing routines, which read data with the data ingestion tools, without using either the visualisation or the GUI). The GUI is using the other layers, and is available for current versions of Windows and Linux operating systems.

The reading (or "ingestion") tools are a data dictionary, based on handbooks and data structures. They free the users of looking at each and every data format, byte by byte, to be able to read their products. The user can select several data files to work on them at the same time. They can be combined if they are of the same kind (same level, same mission or format). Once a dataset is chosen, the user is able to select a geographical area subset chosen by its minimum and maximum longitude and latitude, and/or a temporal subset by its start and end dates, and this for any type of data.

Processing functions are also available, to combine data fields (e.g. addition/subtraction needed to compute sea surface height from satellite altitude, altimetric range and corrections), select them (e.g. data editing to edit out-of-range values), etc. Such formulas can be saved for future use. The toolbox processed outputs are saved in NetCDF, and can be exported in either NetCDf, Ascii or GeoTiff (with a Google Earth export feature). All processing are made through command files where all the parameters are indicated (even when using the GUI, with which the files are automatically generated).

Once processed, the BRAT outputs can be visualised, whether one parameter against one other or against two others (typically, classical maps, including several cartographic projections, but also dispersion plots, or waveforms). For all modes, title and comments can be written by the user. The user is able to choose a colour scale among a pre-defined set. A "do-your-own colour scale" tool is also provided. Plots can be saved in raster (gif, png, tif, jpg) format.

The graphic user interface is an interactive interface, to provide the user with an easy-to-use tool. It enables to use all the above components without writing a single line of programme or command files. In that frame, users are able to save the data context for future work: they are able to save their set preferences for future uses, under a user-defined name, the area, period, mission, colour scale, type of visualisation and the parameters combinations they might have defined.


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Tutorial produced by CLS under contract to ESA and CNES