GRAV-D Project Update Vicki Childers, Ph.D. GRAV-D Project Manager

Replace the Vertical Datum of the USA by 2022 (at today’s funding) with a gravimetric geoid accurate to 1 cm Orthometric heights accessed via GNSS accurate to 2 cm Three thrusts of project: –Airborne gravity survey of entire country and its holdings –Long-term monitoring of geoid change –Partnership surveys Working to launch a collaborative effort with the USGS for simultaneous magnetic measurement Gravity for the Redefinition of the American Vertical Datum (GRAV-D) January 10, Federal Geodetic Control Subcommittee Meeting

January 10, Building a Gravity Field Long Wavelengths: (≥ 350 km) GRACE and GOCE (not shown) Intermediate Wavelengths (500 km to 20 km) Airborne Measurement Surface Measurement Short Wavelengths (< 100 km) + + Federal Geodetic Control Subcommittee Meeting

January 10, 2012 Federal Geodetic Control Subcommittee Meeting 4 Ship gravity Terrestrial gravity New Orleans km gravity gaps along coast Field is not sampled uniformly Data range in age and quality, some w/o metadata Some surveys have systematic errors Data gaps in littoral areas Problems with Gravity Holdings

GRAV-D Update 5 Alaska FY8-12West Coast FY11 Great Lakes FY11-13 FY8-10 = Green FY11 = Blue FY12 = Orange FY13 = White FY12 Texas 15.6% of total area is surveyed (as of ) January 10, 2012 Federal Geodetic Control Subcommittee Meeting

GRAV-D Aircraft NOAA – Gulfstream Jet Prop – NOAA P-3 Hurricane Hunter DOI Bureau of Land Management – Pilatus PC-12 Fugro – King Air E-90A Naval Research Lab – King Air RC-12 January 10, 2012 Federal Geodetic Control Subcommittee Meeting 6 Pilatus PC-12 King Air E-90A

Federal Geodetic Control Subcommittee Meeting Data Distribution January 10, 20127

Federal Geodetic Control Subcommittee Meeting Data Distribution January 10, 20128

Data Products Detailed map of region Data download link to zip file: – ReadMe text file – gravity data file – supplementary data file – block data user manual – GRAV-D data general user manual – xml metadata – kml block extent and block data lines. Gridded image of gravity data Older versions if available January 10, 2012 Federal Geodetic Control Subcommittee Meeting 9

Future Contracting Plans Minimum of 10% of annual surveying will be contracted out (~100 flight hours/yr) Contract Aircraft Services – FY11 Fugro: 10.7% – FY12 Fugro (estimated): 20.6% If additional funding can be found, the percentage of contract surveying would be increased Explore options for dedicated aircraft enabled for magnetic measurement 11January 10, 2012 Federal Geodetic Control Subcommittee Meeting

GRAV-D Federal Partnerships Department of Interior – Bureau of Land Management: shared use of Pilatus aircraft – US Geological Survey: launching effort to collect simultaneous magnetic measurements Naval Research Laboratory – VXS-1 Squadron aircraft services National Geospatial-Intelligence Agency (NGA) – Funded AK survey in 2009 – Absolute and relative gravimetry coordination 12January 10, 2012 Federal Geodetic Control Subcommittee Meeting

Summary GRAV-D project is on course for completion in 2022 Involvement with contract data services is planned at the 10% level minimum The new vertical datum produced by this effort will be invaluable for all geospatial concerns 13January 10, 2012 Federal Geodetic Control Subcommittee Meeting

GRAV-D Contracting Expenditures Contract employees: – FY11: 24.5% of total expenditures – FY12 (planned): 24.8% Contract Surveys – FY11 Fugro: 10.7% – FY12 Fugro (estimated): 20.6% Fugro – Provided aircraft and operator in FY11 – Exploring option for data products in FY12 10January 10, 2012 Federal Geodetic Control Subcommittee Meeting

Geoid Slope Validation Survey January 10, 2012 Federal Geodetic Control Subcommittee Meeting km 218 points 1.5 km apart Austin Rockport Observe geoid shape (slope) using multiple independent terrestrial survey methods – GPS + Leveling – Deflections of the Vertical Compare observed slopes (from terrestrial surveys) to modeled slopes (from gravimetry or satellites) – With / Without new GRAV-D airborne gravity

Geoid Slope Survey Conclusions Including airborne gravity data improves geoid slope accuracy at nearly all distances <325 km The NGS geoid in the TX survey meets the 1 cm accuracy objective only if airborne data are included – No other model achieved 1 cm accuracy Gravimetric geoid models and GPS are a viable alternative to long-line leveling January 10, 2012 Federal Geodetic Control Subcommittee Meeting 15