Characteristics & Performance of GOCE based Gravity Field Models

Characteristics & Performance of GOCE based Gravity Field Models Th. Gruber, R. Rummel Institute of Astronomical & Physical Geodesy (IAPG) Technische Universität München

EGU EGU General General Assembly Assembly 2012, 2012, Session Session G4.2, G4.2, 26.4.2012 26.4.2012

Outline 1. GOCE-based Gravity Field Models ¾ Overview ¾ Characteristics

2. Performance Analysis ¾ Estimated Errors ¾ Comparison with independent Data

3. Summary ¾ Conclusions ¾ Recommendations EGU General Assembly 2012, Session G4.2, 26.4.2012

GOCE based Gravity Field Models Overview ESA/HPF Models Model

Data

D/O

GOCE- EGM_GOC_2__20091101T000000_ DIR1 20100110T235959_0002

2M

240

Prior model (combined) plus GOCE orbits & gradiometry

GOCE- EGM_GOC_2__20091101T000000_ TIM1 20100111T000000_0002

2M

224

Pure GOCE (kin. orbits & gradiometry)

GOCE- EGM_GOC_2__20091030T005757_ SPW1 20100111T073815_0002

2M

210

GRACE low d/o plus GOCE gradiometry

GOCE- EGM_GOC_2__20091101T000000_ DIR2 20100630T235959_0002

6M

240

Prior model (GRACE-only) plus GOCE orbits & gradio.

GOCE- EGM_GOC_2__20091101T000000_ TIM2 20100705T235500_0002

6M

250

Pure GOCE (kin. orbits & gradiometry)

GOCE- EGM_GOC_2__20091031T000000_ SPW2 20100705T235959_0001

6M

240

Pure GOCE (kin. Orbits & gradiometry)

GOCE- EGM_GOC_2__20091101T000000_ DIR3 20110419T235959_0001

1Y

240

Prior model (GRACE-only normals) plus GOCE gradio.

GOCE- EGM_GOC_2__20091101T000000_ TIM3 20110430T235959_0001

1Y

250

Pure GOCE (kin. orbits & gradiometry)

GOCE only

Product Name

GOCE + GRACE

Characteristics

GOCE + GRACE+ Terr.

EGU General Assembly 2012, Session G4.2, 26.4.2012

GOCE based Gravity Field Models Overview additional Models Model

GOCE

Other

D/O

GOCO01S

2M

GRACE

224

ITG2010S normal equations plus GOCE TIM1 model

GOCO02S

6M

GRACE CHAMP SLR

240

ITG2010S normal equations plus GOCE TIM2 model plus SLR to 5 satellites

EIGEN-6S

6.7M

GRACE SLR

240

6.5 years LAGEOS, 6.5 years GRACE

6.7M

GRACE SLR DTU2010

1420

EIGEN-6S plus DTU2010 altimetric gravity with EGM2008 gravity over land

1Y

GRACE CHAMP SLR

250

ITG2010S normal equations plus GOCE TIM3 model plus SLR to 5 satellites

EIGEN-6C GOCO03S (planned)

GOCE only

GOCE + GRACE

Characteristics

GOCE + GRACE+ Terr.

EGU General Assembly 2012, Session G4.2, 26.4.2012

GOCE based Gravity Field Models Overview Models

EGU General Assembly 2012, Session G4.2, 26.4.2012

GOCE based Gravity Field Models Characteristics – Gravity Field Signal

Full signal content of most recent GOCE models up to d/o 180

EGU General Assembly 2012, Session G4.2, 26.4.2012

GOCE based Gravity Field Models Characteristics – Gravity Field Error Coefficients Standard Deviations (log10)

GOCE-DIR3

GOCO02S

GOCE-TIM3

EIGEN-6S

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Estimated Errors Geoid Height Errors from full VCM

Cumulative Geoid Error 0.08

GOCE-TIM1 GOCE-TIM2 GOCE-DIR3 GOCE-TIM3 GOCO02S EIGEN-6S

GOCE-DIR3 (d/o 240)

Cummulative Geoid Error [m]

0.07 0.06

5.7 cm

0.05 0.04 0.03

3.2 cm

0.02 0.01 0

GOCE-TIM3 (d/o 250)

0

100 Degree

200

GOCE Mission Goal

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Comparison with independent Data Geoid Differences at GPS/Levelling Points. Omission Error estimated from EGM2008. RMS of Differences per Truncation Degree (Germany)

GOCE-TIM1

GOCE-TIM2

6.1 cm

GOCE-TIM3

EGM2008

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Comparison with independent Data Geoid Differences at GPS/Levelling Points. Omission Error estimated from EGM2008. RMS of Differences per Truncation Degree (Japan)

RMS of Differences per Truncation Degree (Australia) 0.26

GOCE-DIR3 GOCE-TIM1 GOCE-TIM2 GOCE-TIM3 GOCO02S EIGEN-6C EGM2008

0.13

0.12

RMS Geoid Height Difference [m]

RMS Geoid Height Difference [m]

0.14

0.11

0.1

0.09

50

100

150

Degree

200

GOCE-DIR3 GOCE-TIM1 GOCE-TIM2 GOCE-TIM3 GOCO02S EIGEN-6C EGM2008

0.25

0.24

0.23

50

100

EGU General Assembly 2012, Session G4.2, 26.4.2012

150

Degree

200

250

Performance Analysis Comparison with independent Data EGM2008 Data Coverage & Coverage of GPS/Levelling Data

GPS/ LEVELLING POINTS

12.0% of Land

42.9% of Land

45.1% of Land

Source: Nikolaos K. Pavlis, Simon A. Holmes,Steve C. Kenyon, and John K. Factor: An Earth Gravitational Model to Degree 2160 EGM2008

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Comparison with independent Data Difference of GOCE Models to EGM2008 in South America (d/o 200) [mgal] GOCE-TIM1

GOCE-TIM2

GPS/LEVELLING POINTS in Brazil

GOCE-TIM3

The geodetic data for this study were provided by Brazilian Institute of Geography and Statistics IBGE, Directorate of Geosciences - DGC, Coordination of Geodesy - CGED

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Comparison with independent Data GOCE-TIM3

Geoid Height Differences at GPS/Levelling Points in Brazil. Omission Error estimated from EGM2008. GOCE-TIM3

GPS/LEVELLING POINTS in Brazil

EGM2008

The geodetic data for this study were provided by Brazilian Institute of Geography and Statistics IBGE, Directorate of Geosciences - DGC, Coordination of Geodesy - CGED

EGU General Assembly 2012, Session G4.2, 26.4.2012

Performance Analysis Comparison with independent Data RMS of Geoid Height Differences at GPS/Levelling Points in Brazil per Truncation Degree. Omission Error estimated from EGM2008.

EGU General Assembly 2012, Session G4.2, 26.4.2012

Summary Conclusions & Recommendations ¾ ¾

¾

¾

¾ ¾

GOCE data provide significant new information for the medium to higher spatial resolution of the static Earth’s gravity field. From error estimates and results obtained from comparison with high quality GPS/Levelling data one could conclude that the GOCE geoid accuracy is at a level of 4-5 cm at degree 200 (taking into account the levelling errors). In areas with less good ground coverage of gravity data a significant improvement of the geoid accuracy for the spectral range between degree 100 and 200 can identified (Brazil). These improvements can be completely addressed to GOCE data. For high resolution static field applications (>d/o 180) GOCE-only fields show similar performance as GRACE/GOCE combinations (for GOCE covered areas). For applications needing best performance in the spectral band below d/o 180, or in polar areas GRACE/GOCE combinations are superior. Combined models with terrestrial data shall only be used in areas, where good terrestrial/altimetric gravity information is available. Otherwise GOCE-only or GRACE/GOCE models provide better performance. EGU General Assembly 2012, Session G4.2, 26.4.2012