Comparison of Gravimetric Geoid Models Over the Great Lakes Region

Daniel R. Roman and Xiaopeng Li

Surface Gravity ObservationsSaleh et al. (2012) Fig. 11 Biases of all 244 significantly biased surveys

Saleh et al. (2012) Fig. 12 The effect of significant gravity biases on the geoid

Collection in August 2013, very likely to complete

Collection possible in Aug/Sept 2013,

unlikely to complete

Collection in Sept/Oct 2013, likely to complete

Gravity for the Redefinition of the American Vertical Datum (GRAV-D)Great Lakes Airborne Gravity Collection Effort

Aerogravity – GOCE DIR Rel. 4

Great Lakes GPSBM Locations (NAVD 88)

Alternatives:

• SEPT 12

• NOV 07

• Min. Constr. GPSBM’s (WI)

Great Lakes Errors: SatelliteDegree Cutoff vs. GPSBM’s

Two separate nadir points at degrees100 and 180: must try both

Great Lakes Errors: AerogravityDegree Cutoff vs. GPSBM’s

Degree 280 yields lowest overall error as EGM2008 is cut in at higher harmonics

2.E GRAV-D Surface Gravity Error Detection and Cleaning

• Check terrestrial gravity at suspect sites noted by Saleh et al. (2012)

• Determine and remove potential biases trends in 40 km and longer bandwidth

Errors Detected by GOCE DIR Rel. 4

Location is western New York State and the southeastern portion of Lake Ontario

Errors Detected by Aerogravity

Location is western New York State and the southeastern portion of Lake Ontario

Surface Gravity Anomalies (SGA)

Location is western New York State and the southeastern portion of Lake Ontario

SGA – EGM2008 quiet

SGA – EGM2008/GOCE-DIR R. 4noise

SGA – EGM2008/GOCE/Aerogravitynoiser

CGG2013M8 – CGG2010

Model 8:

• GOCE DIR Release 4

• Surface gravity

• Modified Kernel with Cosine filter between 140-200

CGG2013M8 – USGG2012

4. Conclusions

• Aerogravity bridges the gap between satellite and surface gravity data

• Suspect surface gravity data was confirmed• Assessment of cleaning of surface data and

potential impact is ongoing• With adoption of common W0 and use of

aerogravity to constrain middle wavelengths, a common gravity field model is possible

5. Future Work

• Use NOV 07, SEPT 12, & M.C. GPSBM to model• Test all surface gravity data in region• Develop regional model spanning same region

as CGG2013• Compare final CGG2013 against USGG2012,

XGG13D, and any follow-on models• Test against tide gauges/MODT• Water level gauges on Lakes