GOCE User Toolbox

J. Benveniste

The GOCE User Toolbox

Jérôme Benveniste1

Per Knudsen2 and the GUTS Team

1ESA

Earth Observation Science, Applications and Future

Technologies Department(ESRIN, via Galileo Galilei, Frascati, 00044 RM, Italy)

2Danish National Space Center, Copenhagen, DK

GOCE User Toolbox

J. Benveniste

• Oceanographers wish to derive absolute dynamic

topography (SSH-geoid) + errors

! A User Toolbox would help users attempt to compute

! dynamic topography

! geoid slopes

! error covariances anywhere

! A User Toolbox would help develop and validate new algorithms

! Absolute dynamic topography along radar altimeter tracks

! Gridded dynamic topography

! Gridded mean dynamic topography (MSS - geoid)

… At user required resolutions

Need of a GOCE User Toolbox?

GOCE User Toolbox

J. Benveniste

• Clear and detailed recommendation from the

to develop this toolbox

• See summary and recommendations

in WS proceedings (SP-659)

Need of a User Toolbox!

GOCE User Toolbox

J. Benveniste

Two phase approach

1) Consolidate the User Requirements, write

processing algorithms and input-output

Specs, draft a Toolbox architecture -- By

scientists

– This is “GUTS”

2) Detailed design, coding and testing -- by SW

company + beta testing by scientists

– This will be initiated as “phase 2”

User Toolbox Development Approach

GOCE User Toolbox

J. Benveniste

• Tasks to be performed

– Task 1: User Requirement Consolidation

• covering both Oceanography, SE and Geodesy

– Task 2: Processing Algorithm Scientific Trade

Off Study

– Task 3: Toolbox System Documentation

First Phase: .

GOCE User Toolbox Specification

GOCE User Toolbox

J. Benveniste

• Main requirements

– Computation of global gridded geoid heights at a given order/degree of spherical

expansion (i.e. at a given spatial resolution).

– Computation of geoid heights at a given spatial resolution and a given point or list

of points (unstructured grid, oceanographic transect)

– Option to replace geoid heights by geoid slopes

– Computation of full covariance matrix for a given order/degree of spherical

expansion and/or within a given order/degree range

– Computation of geoid heights covariance for any couple of points on the sphere

– Computation of cumulated geoid height errors at a given spatial resolution (on a

global regular grid or for a list of points)

– Option to include the omission errors

Task 1: User Requirement Consolidation

GOCE User Toolbox

J. Benveniste

Task 1: User Requirement Consolidation

• Additional requirements regarding the computation of

absolute dynamic topography

– Handling of external MSSH (ancillary data)

– Interpolation of MSSH on a given regular grid or at given points

(unstructured grid)

– Spatial filtering of MSSH

– Change of reference system for the geoid and/or MSSH (reference

ellipsoid, tide system)

– Computation of a ‘GOCE’ MDT (MSSH-GOCE geoid) at a given

resolution and on a given structured or unstructured grid

– Handling of altimetric data (altimetric heights, sea level anomalies)

– Computation of altimetric absolute dynamic topography

– Computation of altimetric absolute geostrophic velocities

GOCE User Toolbox

J. Benveniste

• Additional requirements regarding the geoid

validation– Handling of ancillary data (in-situ data, external MDT (in-

situ/modelled), local geoids, combined CHAMP/GRACE/GOCE

geoid…)

– Computation of differences / Root Mean Square differences /

correlation coefficient / regression slopes between GOCE geoid

and external geoids / ‘GOCE’ MDT and external MDT / between

absolute altimetric dynamic topography and in-situ absolute

dynamic topography / between absolute altimetric geostrophic

velocities and in situ geostrophic velocities…

Task 1: User Requirement Consolidation

GOCE User Toolbox

J. Benveniste

Task 2: Scientific Trade Off Study

• A trade off study is needed to select the best (accuracy, CPU time…)

algorithms to compute the variables listed in the user requirement doc.

• Task: Carry out a scientific trade off study (in view of selecting the

toolbox processing and viewing functions)

1) Basic processing functions (filtering functions like spherical harmonic

expansion, interpolation functions)

2) Specific processing function (geoid height covariance computation,

computation of the geoid height and MSSH in respect to a different

reference ellipsoid / tide system, MDT - and corresponding geostrophic

circulation- computation, ADT -and corresponding geostrophic

circulation- computation)

3) Basic viewing functions (global/regional maps, geoid/MDT/MSSH

profile along a transect)

GOCE User Toolbox

J. Benveniste

Task 3: Toolbox System Documentation

• Documentation needed to produce a toolbox:-

1) Input / output specification document,

2) an algorithm specification document

3) architectural design document mapping the required

functionality and interfaces.

4) Provide a summary study report with scope of tutorial for future

toolbox user

• These 4 documents will be the input to the Toolbox

implementation phase.

GOCE User Toolbox

J. Benveniste

Open Source / Open Group

• The consortium is an open working group

• Open to any further membership

• Open to all donators of Open Source code

– Quite numerous as was observed at GOCINA WS

• Consortium meet in workshop style progress

meetings

• Study duration 12 months, end January 2007

GOCE User Toolbox

J. Benveniste

GUTS Participants• H. SNAITH NOCS

• K. HAINES/D. BRETHERTON UREADS

• C. HUGHES/R.BINGHAM POL

• J. JOHANNESSEN NERSC

• P. KNUDSEN DNSC

• P. LEGRAND IFREMER

• M.-H. RIO CLS

• R. RUMMEL/T. GRUBER TUM

• M. LOSCH AWI

• N. SNEEUW UST

• D. STAMMER/F.SIEGISMUND UHH

• C.TSCHERNING UCPH

• F. VOSSEPOEL SRON/UU

GOCE User Toolbox

J. Benveniste

GUTS Task reports

15:10Per Knudsen, Ole

Andersen and Toke

Beck Andersson

Optimal filtering of mean dynamic topography

models

PosterPer Knudsen and the

GUTS Team

Consolidating User Requirements for the GOCE

User Toolbox

PosterMarie-Hélène RioThe GOCE User Toolbox: Toward a first

prototype

PosterKeith Haines and

Daniel Bretherton

GOCE User Toolbox Specification (GUTS) -

System Specification and Architectural Design

PosterFrank Siegismund,

Helen Snaith, Per

Knudsen and the

GUTS Team

GOCE User Toolbox Specification: Scientific

trade off study and algorithm specification

14:50Rory Bingham, Keith

Haines and Chris

Hughes

Elementary Algorithms for Determining the

Ocean Dynamic Topography From Altimetric and

Gravity Data

GOCE User Toolbox

J. Benveniste

GUT Implementation

• Next phase, Toolbox implementation, to start in

January 2007