NOAA’s National Geodetic Survey

United States Height Reference System Modernization Plan

Ottawa, CanadaApril 21, 2009

Ronnie L. TaylorChief, State Advisor Branch

Differential Leveling – NAVD88

Why isn’t NAVD 88 good enough anymore?• NAVD88 defined through leveling network

• Leveling the country can not be done again– At $3000 / km, re-leveling NAVD 88 would cost $2.25 Billion– Does not include densifying poorly covered areas in Western

CONUS, Alaska– Does not include leveling needed for separate vertical

datums on island states and territories

• Leveling yields cross-country error build-up; problems in the mountains

• Leveling requires leaving behind marks – Bulldozers and crustal motion do their worst

“Maintain-able?”

Height Modernization is …

…the establishment of accurate, reliable heights using GNSS technology in conjunction with traditional leveling, gravity, and modern remote sensing information….

• In 2000, $500K added to NGS’ budget for Height Modernization planning

• In 2001, $2.25M added to NGS budget – to implement Height Modernization in NC– to support the California Spatial Reference

Center (CSRC)– to support NGS related Height Modernization

activities• Also in 2001, NOAA is directed to work

with LA and WI to assess their requirements for Height Modernization

The Roots of Height Modernization

Height Modernization Program Timeline• 2002-2006 – Program expanded to 11

states through Congressionally directed earmarks

• 2007 – Program funded at previous year’s levels but without Congressional Direction

• 2008 – Appropriations includes Height Modernization line plus earmarks, but total funding is decreased

FY07 Height Modernization - RecipientsCA Scripps Institution of Oceanography (CSRC)

NC North Carolina Department of Environmental and Natural Resources (and North Carolina A&T State University)

LA Louisiana State University (LSRC)WI Wisconsin Department of Transportation SC South Carolina Geodetic SurveyAL Alabama Department of RevenueMS University of Southern Mississippi

WA Washington State Department of Natural Resources (SRCW)

TX Texas A&M University, Corpus Christi (TSRC)KY Morehead State UniversityAZ Arizona State Land Development (ASRC)IL Illinois State Geological Survey

Height Mod objectives achieved

• Consistent, accurate vertical AND horizontal control network– Rebuild decimated network– New network is GPS-able– Reduces survey costs by providing denser control

• Build capacity in the surveying community to perform the surveys and properly use the data

• Provide data to build better models (DEMs, geoid, storm surge) and products (FIRMs)

• Provide access to NSRS to enable expansion of applications, like RTK, GIS

• Program Management• Congressional briefings• Budget, grants management

• Transition from earmark to line• Transition to competitive awards, agreements

• Coordination – within, between Regions• Partner with Regional Leaders, SRCs

NGS’ Role and Responsibilities

•Project Leadership• Support program growth, long range plan • Specifications, guidelines• Partner with Regional Leaders, SRCs• Support advance of science• Support NOAA’s Mission – shoreline, weather, climate change

NGS’ Role and Responsibilities

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• Outreach/Technology Transfer • Advisors• Forums, workshops• Conferences• Publications, web site• Training, capacity building

NGS’ Role and Responsibilities

• Quality Control • Build outside capacity in geodetic field and processing practices• Provide quality control data• Validate and load projects into NGS database – NGS Certified

• Future • Online submission of data - OPUS

NGS’ Role and Responsibilities

www.ngs.noaa.gov/corbin/index.shtml

Training center in Corbin, VA

• Field training – leveling, RTK and static GPS

• Processing – ADJUST, PAGES, Leveling processing, OPUS

•“OPUS Variety Pack” • OPUS-DB in beta/de-bug mode • OPUS-Projects in development, field testing with Katrina project• OPUS-RS is now available• What next? …. OPUS Levels?

• Research and Development • Development of software, tools

• Online Tool Kit, OPUS, VDatum• Field tools – PGM, Digital Level Tool

• Guidelines for use of new technologies and processes like remote sensing, real time • Modeling – atmospheric, 1-cm geoid• Antenna calibrations

NGS’ Roles and Responsibilities

• Continue to Build on Partnerships- State Agencies - NCGS, SCGS, WiDOT, ALDOR, WADNR, AZSLD- Spatial Reference Centers – CA, LA, WA, TX, AZ- Universities – Scripps, LSU, USM, TAMUCC, NCA&T, Morehead State- NOAA and other Federal Agencies – USACE, USGS, FEMA

NGS’ Roles and Responsibilities

Height Modernization Objective

NSRS

ReliableCost-effective

AccurateStandardized Legally Established

NSRS

GEODETIC CONTROLNAVD88

• GGPSBM2003: 14,185 total 579 Canada STDEV 4.8 cm (2σ)

• GGPSBM1999: 6,169 total 0 Canada STDEV 9.2 cm (2σ)

Why isn’t NAVD 88 good enough anymore?• The GPS era brought fast, accurate ellipsoid heights –

naturally this drove a desire for fast, accurate orthometric heights

• Leveling the country could be done again but;– Too costly in time and money

• Leveling yields cross-country error build-up; problems in the mountains

• Leveling requires leaving behind marks – Bulldozers and crustal motion do their worst

• NAVD 88 H=0 level is known not to be the geoid– Biases , Tilts

• Access to accurate, reliable heights nationally

• Standards that are consistent across the nation

• Data, technology, and tools that yield consistent results regardless of terrain and circumstances

• A system/process that will stand the test of time – “Maintain-able”

Goals of HMP

Consistency?

Funding

GPS on BMs

Gravity

The National Geodetic Survey 10 year plan -- Mission, Vision and Strategy 2008-2018

• Official NGS policy as of Jan 9, 2008– Mission Focused– Modernized Agency– Attention to accuracy– Attention to time-changes– Improved products and services– Integration with other fed missions– www.ngs.noaa.gov/10yearplan

• 2018 Targets:– NAD 83 and NAVD 88 replaced– Cm-accuracy access to all coordinates– Customer-focused agency– Global scientific leadership

From the 10 year plan:“The NSRS must be more accurate than all activities which build upon it, while still being practically achievable”

• You can’t get orthometric height accuracy of a centimeter, when the vertical datum has a half meter bias and one meter tilt across the country.

• You can’t have mm/year accuracy in absolute sea level rise when the NSRS is built on an ITRF accuracy of cm/year

• “The era of using geodetic leveling for continent-scale vertical datum definition comes to an end.”

• Official NGS policy as of Nov 14, 2007– $38.5M over 10 years

• Airborne Gravity Snapshot

• Absolute Gravity Tracking

• Re-define the Vertical Datum of the USA by 2017

Transition to the Future – GRAV-DGravity for the Redefinition of the American Vertical

DatumA Plan (released Dec 2007)

Gravity Survey Plan

• National High Resolution Snapshot

– Predominantly through airborne gravity

– With Absolute Gravity for ties and checks

– Relative Gravity for expanding local regions where airborne shows significant mismatch with existing terrestrial

GRAV-D is the most ambitious project within the National Height Mod Program

• National Height Modernization needs to support the NAVD 88 while transitioning (via GRAV-D) to a new vertical datum in 10 years

• All National Height Mod funds (internal or grants) should support access to accurate heights, in general, but:– With emphasis on NAVD 88 today– With emphasis on the new vertical datum in 5

years

From the 10 year plan:

“The culmination of all these efforts [GRAV-D] allows fast, accurate determination of heights through GPS, and thus truly represents “Height Modernization” as originally envisioned..”

• A geoid model computed for all USA lands at 1 cm accuracy wherever possible, and tracked in time to that accuracy to yield 2 cm orthometric heights

• Time tracking will require local help for smallest signals, including gravity surveys and GPS/leveling co-located minimally constrained surveys

NGS 10 year plan (2007-2017)Vision (to achieve the Mission) of NGS

• The NSRS must be more accurate than all activities which build upon it, while still being practically achievable

• The acceleration of gravity at points used in defining the NSRS should have an absolute accuracy of 10 microGals at any time.

• The gravimetric geoid used in defining the NSRS should have an absolute accuracy less than 1 centimeter anyplace at any time.

•Some of the first Alaska work was completed this past Summer. This was piggybacked onto a planned mapping project in and around the Anchorage/Kenai area.

GRAV-D: Campaign IIMonitor Gravity (“Low Resolution Movie”)

•Measure absolute gravity at each point, annually.•Model gravity changes over time.•Convert to geoid changes over time.•Use with tracked GPS stations (CORS) to get orthometric height changes over time.

Program ManagementGrants ProcessOutreach/Technology Transfer Program LeadershipQuality Assurance/ControlResearch and Development Models and Tools

- Gravity/geoid model- V-Datum

NOAA’s Roles and Responsibilities

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• Modeling – atmospheric, 1-cm geoid• Development of software, tools

•Software, Online Tool Kit• OPUS “Variety Pack”• Field tools – PGM, Digital Level Tool• VERTCON, VDatum

• Guidelines for use of new technologies and processes like remote sensing, real time

Models and Tools

• State Geodetic Advisor Program• Forums, workshops• Conferences• Publications, web site• Training, capacity building

Outside Capacity Building

Conclusion• National Height Modernization is a good idea

– Equitable accuracy and access for all states

• Represents a transition from NAVD 88 to a new vertical datum– Maintain the old, prepare the new, pay for

both during the transition

• The goal of GRAV-D, a new GNSS-accessible vertical datum, is the essence of “Height Modernization”