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Basic Radar Altimetry Toolbox& Radar Altimetry Tutorial
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Basic Radar Altimetry Toolbox & Tutorial A new set of tools for all altimetry users
• A Joint project between ESA and CNES, benefiting from 14 years of Aviso’s experience
• Statements:– 15 years of altimetry and at least as many data formats as satellites,– A growing number of non-expert users of the data,– Scientists also need easy-to-use data products and tools!s
• Basic Radar Altimetry Toolbox (BRAT)– Data reading, processing and visualisation – All altimetry data from official data centres since ERS-1 (1991)
• Radar Altimetry Tutorial (RAT) ( http://www.altimetry.info )– A tutorial describing altimetry, for the users– technique, applications and missions – Products fact sheets and data use cases
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Radar Altimetry Tutorial• Applications
– Geodesy & solid Earth– Ocean– Ice– Climate– Weather– Hydrology & land– Coastal
• Data use cases• Altimetry
– How it works– Data flow– Future improvements
• Altimetry missions– Past missions– Current missions– Future missions
• Products– Data– Software– Documentation– Toolbox
http://www.altimetry.info
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Basic Radar Altimetry Toolbox (BRAT)
• Windows & Linux• ERS-1 and 2, Topex/Poseidon, Geosat Follow-on, Jason-1,
Envisat, and the future Cryosat missions. • From Aviso, ESA, PoDaac, Noaa• From Sensor Geophysical Data Record to gridded merged
data• Four main components:
1. Data reading
2. Processing routine functions
3. Visualisation functions
4. Graphic User Interface (GUI)
5. Save/restore capabilities for workspaces, operations, parameterisation, etc (data and methods re-use or exchange between users).
• Present version: v1.0.2
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Maps (different projections)
Data visualisation
Curves
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Formulas: editing and computing data
• Formulas are combinations of data fields and functions (including arithmetic operators, + - / *)
• Use: – as a ‘data expression’: to compute a combination of data fields (e.g.
SSH)– or as a data selection: to do a complex selection on the data fields
• Pre-defined formulas can be used• User-made formulas can be saved• And re-used in either the same workspace, or imported in
another one
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Editing data
• Data editing is necessary to remove altimeter measurements having lower accuracy
editing using flags e.g. altim_landocean_flag = 0 (to check for values over ocean only in Envisat GDRs)
editing using thresholds E.g. -130 m < altitude –range < 100 m
0 m < SWH < 11 m-0.5 m < wet tropo corr < -0.001 m-0.2 deg² < antenna mispointing < 0.11 deg² …
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Data editing
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Mean Sea Level Anomalies for November 1997
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Eddy Kinetic Energy on 17 August 2005
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Sea Level Anomalies Standard deviation over November 1997
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Hydrology : Aral Sea
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1993
2002
Aral Sea level height from T/P GDR data nearly ten years apart
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For more information
• http://www.altimetry.info (mirror on http://earth.esa.int/brat/ )
Or
• Ask me for a demonstration this week (also at Envisat Symposium late April in Montreux)