National Height Modernization ProgramRenee Shields

Christine Gallagher

Great Lakes Region Height Modernization Consortium Fall Meeting 2012Lansing, Michigan

Wednesday, October 31, 2012

Overview

• NGS 10-year Plan • Height Modernization Program• Geoid Modeling at NGS

NGS Mission Statement

To define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation’s economic,

social, and environmental needs.

The NSRS is a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation

throughout the United States.

Updating the NGS Ten Year Plan

• Why update?– Half way thru 2008 -2018 plan– Many goals accomplished, others

outdated

• Major changes?– Reflects day to day work and

modernization efforts– Grounded in traditional strategic

planning

• Publication?– Public review completed in fall 2012– Final publication in early 2013

NGS Ten Year Plan (2013 – 2023)

Goal 1: Support Users of the NSRS

• Maintain ability to take in, validate, publish data− Bluebooking and datasheets

• Maintain production of National Shoreline− Shoreline mapping, emergency response

• Maintain airport surveying operational capacity− Aeronautical surveys - QA/QC for FAA

• Maintain geodetic surveying operational capacity− Perform operational geodetic surveys for research and testing,

pilot projects, and training• Maintain online tools

− Provide tools to support users’ collection, processing, analysis of geodetic data

Goal 2: Modernize and Improve the NSRS

• Replace NAD 83– Redefine datum; reduce definitional and access-related errors

• Replace NAVD 88– Redefine datum; reduce definitional and access-related errors

• Re-invent “bluebooking”– Improve efficiency of data submission/delivery software

• Fix toolkit - Improve interoperability of NGS products with commercial software– Improve tools; increase accuracy of transformations and

motion models; increase use of GIS • Better surveying - Improve efficiency and accuracy of

geospatial data collection methodologies– Update guidelines, such as NGS58/59, RTNs

Goal 3: Expand NSRS Stakeholder Base: Partnerships, Outreach, Education

• Process for RTN operators to align to NSRS– Ensure consistency between RTNs and NSRS, and each other; provide guidelines

for use and management• Engage new stakeholders

– Participate in national and regional partner/stakeholder meetings and conferences; build user capacity to perform geodetic surveys, use tools

• Engage universities– Develop college-level seminars; collaborate in research activities

• Dynamic Web presence– Improve responsiveness to users through increased web access, communications

• Grow educational portfolio– Expand training capabilities at Corbin training center and online; develop

comprehensive outreach plan• Integrated Ocean & Coastal Mapping Program (IOCM)

– Identify requirements, develop methodologies for topo and bathy lidar and imagery activities in support of Nautical Charting and Shoreline products

Goal 4: Enable Workforce

• Educate NGS Workforce– Formal and informal training opportunities, rotational

assignments, increase involvement in professional orgs.

• Recruiting – Align Workforce with Mission– Increase number of field and office staff, recruit

university graduates, interns, create open vacancy

• Institutional Knowledge – Define core capabilities, develop succession plan,

mentoring program

Goal 5: Improve Organizational and Administrative Functionality

• Project Management• I.T. Support• Socio-economic Awareness• Records Management• Regional Advisor Program

1994 – Meeting held in Sacramento, CA

1998 – Height Modernization Study funded

2000 – Height Modernization planning

funded

2001 – Height Modernization funds

directed to CA and NC; efforts began to

study need in LA and WI

2002 to 2010 – Program expands to 18

funded states

Height Modernization History

Height Modernization Activity

Height Modernization: future plans

Height Modernization ProgramNational Plan

Height Modernization ProgramNational Plan

Height Modernization ProgramNational Plan

Height Modernization ProgramRecent Activities

Evolution of Height Modernization – Geoid Models and the Vertical Datum

• At the start of Height Mod NGS felt the Gravimetric geoid was adequate as the base for the Hybrid geoid, and that GPS on bench marks would enable continued use of NAVD 88 . . .

What’s changed?• Better accuracy from GNSS-derived heights – can use GNSS

(CORS) to monitor changes in heights• Better understanding of poor condition of vertical network –

which continues to degrade• Gravity holdings at NGS evaluated – impact on accuracy of

USGG

Definitions: GEOIDS versus GEOID HEIGHTS• “The equipotential surface of the Earth’s gravity field which best

fits, in the least squares sense, (global) mean sea level.”*• Can’t see the surface or measure it directly.• Can be modeled from gravity data as they are mathematically

related.• Note that the geoid is a vertical datum surface• A geoid height is the height from an ellipsoidal datum to a geoid.• Hence, geoid height models are directly tied to the geoid and

ellipsoid that define them (i.e., geoid height models are not interchangeable).

*Definition from the Geodetic Glossary, September 1986

In Search of the Geoid…

Courtesy of Natural Resources Canada www.geod.nrcan.gc.ca/index_e/geodesy_e/geoid03_e.html

Dr. Dan Roman

Dr. Xiaopeng Li

Drs. Yan Wang and Simon Holmes not pictured

• Orthometric heights– Measure by leveling surveys– Most accurate but most expensive– Difficult to maintain over time, esp. on national scale

• Ellipsoid heights – Inherent to GNSS measurements– Need accurate ellipsoid height control– Better field procedures = better heights

• Geoid heights– Derived from model developed from gravity observations– Can provide relationship between e.h. and o.h.

Measuring and relating different kinds of heights

(NAVD 88) H

H = Orthometric Height (leveling)

H = h - N

TOPOGRAPHIC SURFACE

h = Ellipsoidal Height (GPS)

N = Geoid Height (model)

h (NAD 83)

Ellipsoid

N

GeoidGeoid Height

(GEOIDxx)

Ellipsoid, Geoid, and Orthometric Heights

With 2 known heights we can calculate the 3rd

NGS’ Two Geoid Models• Gravitational model:

• includes terrestrial and satellite gravity data, EGM08, and the Residual Terrain Model

• is a purely gravitational model and hence good for scientific applications

• does not provide relationship between GPS heights and NAVD 88

• “Hybrid” model:

• starts with gravitational model

• adds well-distributed accurate GPS on bench marks to enable a fit to NAVD 88

Hybrid Geoid Height Models (e.g., GEOID12A), Gravimetric Geoid Height Models (e.g., USGG2012) and Conversion Surfaces using GPS on BM data

• Gravimetric Geoid systematic misfit to BM’s but best fits “true” heights• Hybrid Geoid “converted” to fit local BM’s, so best fits NAVD 88 heights• Conversion Surface model of systematic misfit derived from BM’s in IDB

Earth’s Surface

hh

h hh

HH

HH

H

NNNNN

Ellipsoid

Hybrid Geoid

Gravimetric Geoid Geoid

Control Data for GEOID12 Modeling

Region Reference Frame

Vertical Datum

# GPSBM used (# Rejected)

#OPUSDB used(# Rejected)

CONUS NAD 83 (2011) NAVD 88 * 24,003 (868) 478 (258)

- VTDP Region NAD 83 (2011) NAVD 88/VTDP 357 (153) 1 (17)

Alaska NAD 83 (2011) NAVD 88 ** 105 (4) 2 (1)

Puerto Rico NAD 83 (2011) PRVD 02 38 0

U.S. Virgin Islands NAD 83 (2011) VIVD 09 21 (3) 0

Hawaii NAD 83 (PA11) Geoid (W0) n/a n/a

American Samoa NAD 83 (PA11) ASVD 02 19 (3) 0

Guam NAD 83 (MA11) GUVD 04 33 0

CNMI NAD 83 (MA11) NMVD 03 55 0* Supplemented by 574 (5 rejected) in Canada and 674 (70 rejected) in Mexico** Supplemented by 88 (2 rejected) in Canadahttp://www.ngs.noaa.gov/GEOID/GEOID12/GPSonBM12.shtml

Ellipsoid Height Changes (NA2011-NA2007)

Orthometric Height Changes (mm)

Distribution of OPUSDBBM12

Distribution of OPUSDBBM12

The Impact of OPUS

GEOID12 Error Map for Southwest

Triangles show locations of GPSBM2012 & OPUSDBBM12 control points.

Error increases based on the size of the gap.

Dense coverage yields < 1 cm.

Errors will be provided with GEOID12A hts.

GPSBM1999: 6,169 total 0 Canada STDEV 9.2 cm (2σ) GPSBM2003: 14,185 total 579 Canada STDEV 4.8 cm (2σ) GPSBM2009: 18,291 total 576 Canada STDEV 2.8 cm (2σ)

For 2009 and 12A Rejections based on:S: State adviserh: ell ht err (NRA)H: ortho ht errN: geoid err (misfit)D: duplicate

An additional 6,000 points?

GEOID12 – GEOID09

Release of GEOID12A

GEOID12A - GEOID12

GEOID12A• Complete for all regions

• Converts between NAD 83 (**11) and local vertical datum (NAVD 88 in CONUS)

• Modeling is much the same; new data had an impact:– Additional data in

Mexico– OPUSDBBM12 (i.e. GPS

on Bench Marks from OPUS DB)

VISIT: http://www.ngs.noaa.gov/GEOID/GEOID12A/

GEOID12A is built on USGG2012 – so how good is USGG?

• Most of the historical NGS data is terrestrial• Multiple observers, multiple processors over the past 60

years • Numerous corrections and datums over time• Metadata maintained in paper records• Very limited aerogravity• Deficit in near-shore gravity data

• 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• 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)

June 21, 2012 39Height Mod Partners Meeting

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)

+

+

Continental US

White = FY13Orange = FY12Green = FY11 and earlier

CompleteIn FY13

Alaska

White = FY13Orange = FY12Green = FY11 and earlier

Geoid Slope Validation Survey

• Proof of concept: Does the addition of the airborne data make for a geoid accurate at 1 cm???

June 21, 2012 Height Mod Partners Meeting 43

2011GSVS

June 21, 2012 Height Mod Partners Meeting

325 km218 points1.5 km apart

Austin

Rockport

GPS: 20 identical. units, 10/day leapfrog, 40 hrs ea. Leveling: 1st order, class II, digital barcode levelingGravity: FG-5 and A-10 anchors, 4 L/R in 2 teamsDoV: ETH Zurich DIADEM GPS & camera systemLIDAR: Riegl Q680i-D, 2 pt/m2 spacing, 0.5 km widthImagery: Applanix 439 RGB DualCam, 5000’ AGLOther:

RTN, short-session GPS, extra gravity marks around Austin, gravity gradients

44

2011 GSVS

June 21, 2012 Height Mod Partners Meeting

325 km218 points1.5 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 gravity45

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

June 21, 2012 Height Mod Partners Meeting 46

• Geoid Models Page:– http://www.ngs.noaa.gov/GEOID/

• GRAV-D Page:– http://www.ngs.noaa.gov/GRAV-D/

• Geoid Team: 301-713-3202 – Dan Roman (x161), Yan Wang (x127), Xiaopeng

Li (x210)

• GRAV-D Project Manager: – Vicki Childers 301-713-3211 x161

QUESTIONS?

Renee.Shields@noaa.gov, 301-713-3231, x116Christine.Gallagher@noaa.gov, 301-713-3231 x105