New Vertical Datum: plans, status, GRAV-D updateFGCS

San Diego, CA.July 11, 2011

Mark C. EcklMark C. EcklNGS Chief of Observation and Analysis Division,NGS Chief of Observation and Analysis Division,

New Vertical Datum Project ManagerNew Vertical Datum Project Manager

NORTH AMERICAL VERTICAL DATUM 1988

NEW VERTICAL DATUM(Topics)

• Rationale for the New Vertical Datum

• Components of the Project Plan

• Estimated Outcome

NEW VERTICAL DATUM(Rationale)

• To be consistent with the shift in the geometric reference frame/ellipsoid (2022)

• Improvement in our technical abilities in reference surface realization (geopotential gravimetric reference surface - 1cm accuracy of geoid (GNSS/GRAV-D))

• The new geopotential reference surface will be aligned with the geometric reference frame/ellipsoid (i.e., no hybrid geoid)

• A move away from differentially leveled passive control as the defining mechanism of the reference surface

NEW VERTICAL DATUM(Rationale)

• The technology to make accurate vertical heights measurements with GNSS technology

• To provide vertical access to formerly prohibitive places

• To allow monitoring of physical or geophysical datum deformation

NEW VERTICAL DATUM(Components)

• Design and adopt new geometric reference frame (Geometric Datum Project)

• Realize new geometric datum with existing passive/active control, i.e., a horizontal (geometric) adjustment

• Definition of the W0 surface as the new datum reference surface

• Build a gravimetric geoid with an overall accuracy of 1 cm

GRAV-D Processing Update

• Alabama (‘08) and 2008 Alaska survey already delivered to Geoid team (Newton v1.1)

• Next major version of aerogravity processing software is complete (Newton 1.2)

• Newton 1.2 data for Alabama and Louisiana will be delivered to geoid team by early July; other surveys will quickly follow

• LA/AL airborne gravity data will release publicly in next month via a web page designed to share data

• Still partnering for flights; seeking a dedicated plane

University of New Orleans June 20-21, 2011

Determining Elevations with GNSS Improvements to the Geoid Models

7

GRAV-D Survey Plans

• FY 2011:

– Alaska

– California/Oregon coastline

– Eastern Great Lakes Region

– As of June 1, 13.45% of total area has been surveyed

• FY2012:

– Great Lakes region

– Washington State

– California

• FY2013:

– Finish Great Lakes

– TBD

Alaska FY11 West Coast FY11-12

FY11-13 Great Lakes Plan

FY10 = GreenFY11 = BlueFY12 = OrangeFY13 = White

(FY11 Already Flown)

NEW VERTICAL DATUM(Components)

• Studies of:• Geoid slope validations• Geoid bias• Geoid long term monitoring (i.e., change detection)• Gravity measurement systems accuracy assessments• GNSS ellipsoid absolute height measurements• GNSS differential ellipsoid height measurements

• Prepare a forward and backward vertical datum conversion strategy - points and maps/charts (ref: NC Pilot Project)

NEW VERTICAL DATUM(Components)

• Work with FGCS for adoption of new/updated (FGCS Vertical Working Group):• Standards of Accuracy• Specifications• Procedures, and• Guidelines

• Outreach

NEW VERTICAL DATUM(Outcome)

NEW VERTICAL DATUM(Goal)

Increase the accuracy and utility of the vertical datum by referencing a global geopotential surface, related to global sea-level, which is accessible through space-based measurement systems and which maintains the differential precision associated with any NGS adopted vertical datum.