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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)