NJSPLS Workshop Shields HeightModNJSPLSHandout · Differential Leveling – NAVD88: Accurate? ......

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National Geodetic Survey’s National Height Modernization

Program

New Jersey Society of Professional Land SurveyorsAnnual Conference

Atlantic City, New JerseyFebruary 3-5, 2011

Renee ShieldsHeight Modernization Manager

• NGS Mission and Height Modernization Background and Overview

• Needs and Benefits of Accurate

Overview

• Needs and Benefits of Accurate Heights –Activities: mapping, charting,

construction, models, precision ag–State accomplishments

• Accurate Heights with GPS– Ellipsoid vs. Orthometric heights– Geoid model/GRAV-D– The future of the vertical datum

Overview

– The future of the vertical datum• NGS’ Role

– Delivering the NSRS– Management/coordination– Infrastructure/Models/Outreach

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1807President Thomas Jefferson signs legislation

establishing the Survey of the Coast

Changes in Mission of the USC&GS

• 1867-1871 - with the acquisition of Alaska, mission expanded to carry geodetic surveys into the interior of the country

• 1997 – “apply state-of-of-the-art methods of precise positioning and advanced geodetic techniques to positioning and advanced geodetic techniques to establish and maintain a consistent national coordinate system and to support mapping, charting, navigation, boundary determination, property delineation, infrastructure development, and resource evaluation surveys, and scientific applications”

The National Geodetic Survey 10 year Plan -- Mission, Vision and Strategy

2008-2018

• To define, maintain and provide access to the National Spatial Reference System to meet our nation’s economic, social, and environmental needse o e ta eeds

• 2018 Targets:– NAD 83 and NAVD 88

replaced– Modernize the Geopotential

(Vertical) Datum

http://www.ngs.noaa.gov/INFO/NGS10yearplan.pdf

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• The official national coordinate system of the U.S. federal government which includes:– Geodetic latitude, longitude and height– Scale, gravity, and orientation– How these values change with time

Mission – The NSRS is…

• Components include:– National CORS– Network of passive monuments– Official national shoreline – Precise orbits of GNSS satellites used to define NSRS– Models and tools to describe how all of these

quantities change over time.

• Define the NSRS– “The NSRS must be more accurate than all activities which

build upon it, while still being practicably achievable.”

• Maintain the NSRS– “NGS must track all of the temporal changes to the defining

points of the NSRS in such a way as to always maintain the

From the NGS 10-Year Plan

p y yaccuracy in the NSRS definition.”

• Provide Access to the NSRS– “NGS must develop and maintain guidelines for users to

access the NSRS at a variety of accuracies.”– “NGS will publish all coordinates of defining points of the

NSRS with an epoch tag and will furthermore publish velocities relative to that epoch-tagged set of coordinates”

http://geodesy.noaa.gov/INFO/ngs_tenyearplan.pdf

Height Modernization Objective

NSRS

NSRS

Reliable

Cost-effective

Accurate

Standardized

GEODETIC CONTROLNAVD88

Legally Established

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Height Modernization is …

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

The Roots of Height Modernization

• In 1994 - First meeting held in

Sacramento, CA

– Some heights in CA in error by more than a meter

– GPS could be immediately used to meet some of California’s requirementssome of California’s requirements

– Necessary for the implementation of NAVD 88

• In 1998, $1.0 M was added to NGS budget to perform Height Modernization Study

• 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

The Roots of Height Modernization

– 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

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Height Modernization Program Timeline

• 2002-2006 – Expanded to 11 states through Congressionally directed earmarks

• 2007 – Funded at FY2006 level but without Congressional Direction

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

• 2009-2010 – Appropriations includes HM line plus earmarks (large sums directed at limited number of organizations)

Height Modernization AppropriationsFiscal Year Appropriations States

FY 2001 2.25 M CA, NC

FY 2002 3.75 M CA, NC, LA, WI

FY 2003 3.75 M CA, NC, LA, WI, MS

FY 2004 9.0 M CA, NC, LA, WI, MS, AL, WA, SC

FY 2005 9 6 M CA NC LA WI MS AL WA TX KYFY 2005 9.6 M CA, NC, LA, WI, MS, AL, WA, TX, KY

FY 2006 9.9 M CA, NC, WI, MS, AL, SC, TX, KY, AZ

FY 2007 9.9 M “without direction”

FY 2008 4.995 M + 1.152 M Line* + AL, KY, IL

FY 2009 2.54 M + 9.06 M Line* + AL, MS, LA, IL, WI

FY 2010 2.54 M + 5.27 M Line* + IL, LA, MS, TX, WI

* Competitive grants funded from Line

Height Modernization - Recipients• Academic Institutions

– Scripps Oceanographic Institute – North Carolina A&T University– Louisiana State University– University of Southern Mississippi– Texas A&M Corpus Christi– Morehead State University– University of Illinois

N M i St t U i it– New Mexico State University

• State and Local Governments– North Carolina Geodetic Survey– South Carolina Geodetic Survey– State Departments of Transportation: Wisconsin, Michigan,

Minnesota, Colorado, Montana, New Jersey – Alabama Department of Revenue– Washington State Department of Natural Resources– Arizona State Land Development

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Participating and Interested States

Current Funded Partners

States engaged in HM without federal funding assistance

Spatial Reference CentersRegional LeadersOther funded partners

Height Matters

Image credit:: AP Photo/Rick Bowmer

• Transportation

• Mapping and Charting

• Construction, Engineering

• Recover decimated control networks

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Flooding: river overflow, coastal, storm surge, flash flood

• FEMA Map Modernization Program

– Flood Insurance Rate Maps

– Elevation Certificates

– FEMA Cooperative Technical

• Determining High Water Marks

• Evacuation Route Surveys

• Damage Mitigation

FEMA Cooperative Technical States, e.g. NC

Measure, Monitor, Model - Crustal Motion/ Subsidence/Isostatic Rebound /Seasonal changes

1713

129

MONTGOMERY

17 8 2 911

18

3 5619

15

10 1416

4

0021

26

2322

20

272428

NE

LKHU

ADKSTMC

HOUSTON

FORT BEND

GALVESTON

HARRIS

• Dam Safety

• Water resources

• Relating tidal and geodetic datums

– Ship transport:

Water Resource Management

Folsom dam

Ship transport: underwater/overhead clearance

Novi Special WT, MI

Alma, AR

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DEMs, Geoid modeling

New and Non-traditional Applications:

• Geographic Information Systems (GIS)

• Precision Farming• Fleet Management

• Reduce design and construction costs for engineering projects

• Accurate geospatial foundation for GIS

• Emergency response

• Coastal resilience, habitat restoration

• Water management, delivery – dams, levees

• Water levels – relative sea level change

Benefits

g

• Storm surge, inundation modeling

• Accurate determination of floodplains – maximize insurance cost/benefit

• Improve agricultural yields

• Ensure safe low-visibility aircraft landings

• Ensure safe overhead and under-keel clearance on waterways

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• Access to accurate, reliable heights nationally

• Standards that are consistentacross the nation

Goal of NHMP

• 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”

NGVD 29 NAVD 88

DATUM DEFINITION LMSL 26 Tide Gauges FATHER’S POINT/Rimouski in the U.S. & Canada; Quebec, Canada;Various tidal epochs common epoch (1960-1978)

Vertical Reference Frame Today

GEOID FITTING Distorted to Fit MSL Gauges Best Continental Model

CORRECTIONS Normal Gravity, Level, Observed Gravity, Level, Rod, Temp. Rod, Temp. Magnetic, Refraction

BENCH MARKS 100,000 450,000

LEVELING (Km) 106,724 (U.S. + Canada) 1,001,500

NAVD 88 Tidal Control Stations

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CONUS Range = 0.4 to 5.0 ft (AK ~ 6.5 ft)

0

Height Difference - NGVD29 to NAVD88

0NOAA/NGS

North American Vertical Datum of 1988

June 24, 1993: Federal Register / Vol. 58, No. 120SUMMARY: This Notice announces a decision by the Federal Geodetic Control Subcommittee (FGCS) to affirm the North American Vertical Datum of 1988 (NAVD 88) as the official civilian vertical datum for surveying and mapping activities indatum for surveying and mapping activities in the United States performed or financed by the Federal Government, and to the extent practicable, legally allowable, and feasible,require that all Federal agencies using or producing vertical height information undertake an orderly transition to NAVD 88.

Differential Leveling – NAVD88: Accurate? Maintainable?

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B h M k B

Conventional Leveling:

• Precise

• Labor Intensive

Bench Mark A

Bench Mark B

1 National Geodetic Survey, Retrieval Date = DECEMBER 10, 2010AH9175 ***********************************************************************AH9175 FBN - This is a Federal Base Network Control Station.AH9175 DESIGNATION - 01410600 AAH9175 PID - AH9175AH9175 STATE/COUNTY- NJ/ATLANTICAH9175 USGS QUAD - OCEANVILLE (1989)AH9175AH9175 *CURRENT SURVEY CONTROLAH9175 ___________________________________________________________________AH9175* NAD 83(2007)- 39 22 46.68223(N) 074 25 28.32298(W) ADJUSTED

NGS Datasheet – Leveling

AH9175* NAVD 88 - 1.568 (meters) 5.14 (feet) ADJUSTED AH9175 ___________________________________________________________________AH9175 EPOCH DATE - 2002.00AH9175 . . . AH9175 ELLIP HEIGHT- -32.802 (meters) (02/10/07) ADJUSTEDAH9175 GEOID HEIGHT- -34.34 (meters) GEOID09AH9175 DYNAMIC HT - 1.567 (meters) 5.14 (feet) COMPAH9175AH9175 ------- Accuracy Estimates (at 95% Confidence Level in cm) --------AH9175 Type PID Designation North East EllipAH9175 -------------------------------------------------------------------AH9175 NETWORK AH9175 01410600 A 0.92 0.73 2.12

AH9175 -------------------------------------------------------------------AH9175 NETWORK AH9175 01410600 A 0.92 0.73 2.12AH9175 -------------------------------------------------------------------AH9175 MODELED GRAV- 980,109.0 (mgal) NAVD 88AH9175AH9175 VERT ORDER - SECOND CLASS IAH9175AH9175. . .AH9175AH9175.The orthometric height was determined by differential leveling andAH9175.adjusted in March 2001.


AH9175.No vertical observational check was made to the station.AH9175AH9175.The X, Y, and Z were computed from the position and the ellipsoidal ht.AH9175AH9175.The Laplace correction was computed from DEFLEC09 derived deflections.AH9175AH9175.The ellipsoidal height was determined by GPS observationsAH9175.and is referenced to NAD 83.AH9175AH9175.The geoid height was determined by GEOID09.AH9175

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AH9175AH9175 . . .AH9175AH9175 SUPERSEDED SURVEY CONTROLAH9175AH9175 NAD 83(1996)- 39 22 46.68190(N) 074 25 28.32294(W) AD( ) AAH9175 ELLIP H (09/24/01) -32.787 (m) GP( ) 4 1AH9175 NAVD 88 (09/24/01) 1.57 (m) 5.2 (f) LEVELING 3 AH9175AH9175.Superseded values are not recommended for survey control.AH9175.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.


AH9175.See file dsdata.txt to determine how the superseded data were derived.AH9175 . . .AH9175 HISTORY - Date Condition Report ByAH9175 HISTORY - 1997 MONUMENTED NJGSAH9175 HISTORY - 20000714 GOOD NGSAH9175 HISTORY - 20090106 GOOD BANCAH9175AH9175 STATION DESCRIPTIONAH9175AH9175'DESCRIBED BY NEW JERSEY GEODETIC SURVEY 1997 (ECB)AH9175'THE STATION IS LOCATED IN THE CITY OF ATLANTIC CITY ON THE GROUNDS OFAH9175'THE U.S. COAST GUARD STATION. TO REACH THE STATION FROM THEAH9175'INTERSECTION OF U.S. HIGHWAY 30, ABSECON BOULEVARD AND STATE ROUTE

Pros and Cons of Leveling

• Pros – Produces the most accurate relative heights

possible

• Cons– Expensivep– Time consuming– Requires setting and tying to passive control

which falls victim to subsidence, tectonic motion, isostatic adjustment, and … bulldozers

enter GNSS…

Can we get accurate heights with GNSS?

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• Good ellipsoid heights – Better field procedures– Accurate ellipsoid heights at control

stations

To improve GPS-derived orthometric heights we need:

• An improved geoid model– Accurate ellipsoid heights– More bench marks observed by GPS

• Accurate orthometric heights at bench marks

H = Orthometric Height (leveling) H = h - N

TOPOGRAPHIC SURFACE

h = Ellipsoidal Height (GPS)

N = Geoid Height (model)

h (NAD83)

Accurate:Ellipsoid, Geoid, and Orthometric Heights

(NAVD88) Hh (NAD83)

Ellipsoid

N

GeoidGeoid Height

(GEOID09)

With 2 known heights we can calculate the 3rd

Guidelines to obtain accurate heights through GNSS

NOAA Technical Memorandum NOS NGS-58

GUIDELINES FOR ESTABLISHING GPS-DERIVED ELLIPSOID HEIGHTS(STANDARDS: 2 CM AND 5 CM)VERSION 4.3

David B. ZilkoskiJoseph D. D'OnofrioStephen J. Frakes

Silver Spring, MD

November 1997

• Equipment requirements

• Field Procedures/Data

Collection Parameters

U.S. DEPARTMENT OF National Oceanic and National Ocean National GeodeticCOMMERCE Atmospheric Administration Service Survey

Collection Parameters

• Basic Control Requirements

• Processing/Analysis

Procedures

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Equipment Requirements

• Dual-frequency, full-wavelength GPS receiver– Required - observations > 10 km– Preferred - ALL observations regardless of length

• Geodetic quality antennas with ground planes– Choke ring antennas; highly recommended– Successfully modeled L1/L2 offsets and phase – Successfully modeled L1/L2 offsets and phase

patterns– Use identical antenna types if possible– Corrections must be utilized by processing software

when mixing antenna types

“Fixed” HeightTripod

Equipment Requirements

Data Collection Parameters

• VDOP < 6 for 90% or longer of 30 minute session

• Session lengths and sampling rate• Track satellites down to 10° elevation angle• Repeat Baselines• Repeat Baselines

– Different days– Different times of day

• Detect, remove, reduce effects due to multipath and similar satellite geometry between sessions

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Comparison of 30 Minute Solutions - Precise Orbit; Hopfield (0); IONOFREE(30 Minute solutions computed on the hour and the half hour)

MOLA to RV22 10.8 Km

Day 264dh (m)

Hours Diff. Day 265

dh (m)

Day 264 minus

Day 265 (cm)

* diff >2 cm

Mean dh (m)

Mean dh minus "Truth" (cm)

* diff >2 cm

14:00-14:30 -10.281 27hrs 17:00-17:30 -10.279 -0.2 -10.280 -0.514:30-15:00 -10.278 27hrs 17:30-18:00 -10.270 -0.8 -10.274 0.215:00-15:30 -10.281 27hrs 18:00-18:30 -10.278 -0.3 -10.280 -0.4

Two Days/Same Time

Difference = 0.3 cm

“Truth” = -10.276Difference = 2.3 cm

Two Days/Different Times

-10.254-10.251 > -10.253

15:30-16:00 -10.291 27hrs 18:30-19:00 -10.274 -1.7 -10.283 -0.716:00-16:30 -10.274 27hrs 19:00-19:30 -10.274 0.0 -10.274 0.216:30-17:00 -10.287 27hrs 19:30-20:00 -10.276 -1.1 -10.282 -0.617:00-17:30 -10.279 27hrs 20:00-20:30 -10.261 -1.8 -10.270 0.617:30-18:00 -10.270 27hrs 20:30-21:00 -10.251 -1.9 -10.261 1.518:00-18:30 -10.277 21hrs 15:00-15:30 -10.270 -0.7 -10.274 0.218:30-19:00 -10.271 21hrs 15:30-16:00 -10.276 0.5 -10.274 0.219:00-19:30 -10.277 21hrs 16:00-16:30 -10.278 0.1 -10.278 -0.219:30-20:00 -10.271 21hrs 16:30-17:00 -10.286 1.5 -10.279 -0.320:00-20:30 -10.259 18hrs 14:00-14:30 -10.278 1.9 -10.269 0.720:30-21:00 -10.254 18hrs 14:30-15:00 -10.295 4.1 * -10.275 0.1

"Truth"14:00-21:00 -10.275 14:00-21:00 -10.276 0.1 -10.276

-10.254- 10.295 > -10.275

Difference = 4.1 cm

“Truth” = -10.276

Difference = 0.1 cm

REPEAT BASELINE DIFFERENCES BY DISTANCE

2

3

4

5

6

T D

IFFE

REN

CES

(CM

)

0113-H83A3.1

1933-01213.1 0092-1933

3.1

6669-00924.7

6669-6666 4.9

172 BASELINES - 3% Above 3 cm

0

1

2

0 5000 10000 15000 20000 25000 30000 35000 40000

BASELINE LENGTH (M)

REP

EAT

Station pairs with large repeat base line differences also result in large residuals. NGS guidelines for estimating GPS-derived ellipsoid heights require user to re-observe these base lines.

Four Basic Control Requirements

• Occupy stations with known NAVD 88 orthometric heights, evenly distributed throughout project

• Project areas < 20 km on a side, surround project with at least 4 NAVD 88 bench marks

• Project areas > 20 km on a side, keep distances between GPS-occupied NAVD 88 bench marks to less than 20 km

• Projects located in mountainous regions, occupy bench marks at base and summit of mountains, even if distance is less than 20 km

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• Perform 3-D minimally constrained (free) adjustment

• Analyze adjustment results

• Compute differences between GPS-derived orthometric heights from free adjustment

d bli h d NAVD88 BM

Processing: Five Basic Procedures

and published NAVD88 BMs

• Evaluate differences to determine which BMs have valid NAVD88 height values

• Perform constrained adjustment with results from previous step

HARN/Control Stations(75 km) 5.5 hr 3 days different times

Primary Base(40 km) 5.5 hr

3 days different times

GPS Ellipsoid Height Hierarchy


Secondary Base(15 km) 0.5 hr


Local Network Stations(7 to 10 km) 0.5 hr


Sample Project

• Area: East San Francisco Bay Project– Latitude 37° 50” N to 38° 10” N– Longitude 121° 45” W to 122° 25” W

• Receivers Available: 5

• Standards: 2 cm GPS-Derived Heights

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East SF Bay Project Primary Base Stations

CORSHARNNAVD’88 BMNew Station

38°20’N

Primary Base Station

10CCD191

121°40’W122°35’W LONGITUDE

MOLA

MARTLAKE

38°16’NCORSHARNNAVD’88 BMNew StationSpacing StationPrimary Base Station

10LC

TIDD D191

MONT X469 Z190DROU

BM20 Q555

East Bay Project Points


04KU

TIDE

ZINCPT14

MART

5144

P371R100

LAKE04HK

CATT

Q

TOLA

CORSHARNNAVD’88 BMNew StationSpacing Station

38°16’N


Session DSession ESession F

Session G

Observation Sessions


Session A

Session B Session C

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CORSHARNNAVD’88 BMNew StationSpacing Station

38°16’N


Independent Base Lines

D

DD

E

E

E

E

FF

F

F

G

G


A

A

A

AB

B

B

B

C

C C

C

D

G

GG

Height Modernization ProjectHARN - Average 50km,

max 75kmPrimary – 20-25km,

max 40km

Secondary - Average 12-15km, max 15km

Local – Average 6-8 km, max 10km

= Existing NGS Level line= New HMP Level line

= HARN

= Primary Base Network

= Secondary Base Network

= Local Base Network

NJOC – Sussex County, NJ

Primary Control, New Jersey – CORS

NJWC – Warren County, NJ

NJGT – R Stockton Coll, NJ

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Primary Control:New Jersey

High Acc ac High Accuracy Reference Network

(1999/2002)




1 National Geodetic Survey, Retrieval Date = DECEMBER 15, 2010JU4311 ***********************************************************************JU4311 DESIGNATION - NJGPS 20JU4311 PID - JU4311JU4311 STATE/COUNTY- NJ/ATLANTICJU4311 USGS QUAD - OCEANVILLE (1989)JU4311JU4311 *CURRENT SURVEY CONTROLJU4311 ___________________________________________________________________JU4311* NAD 83(2007)- 39 23 01.97707(N) 074 25 31.29384(W) ADJUSTED JU4311* NAVD 88 - 22.0 (meters) 72. (feet) GPS OBS

NGS Datasheet – Standard GNSS

JU4311 ___________________________________________________________________JU4311 . . . .JU4311 LAPLACE CORR- -2.46 (seconds) DEFLEC09JU4311 ELLIP HEIGHT- -12.333 (meters) (02/10/07) ADJUSTEDJU4311 GEOID HEIGHT- -34.32 (meters) GEOID09JU4311JU4311 ------- Accuracy Estimates (at 95% Confidence Level in cm) --------JU4311 Type PID Designation North East EllipJU4311 -------------------------------------------------------------------JU4311 NETWORK JU4311 NJGPS 20 0.67 0.57 1.37JU4311.The orthometric height was determined by GPS observations and a

JU4311.high-resolution geoid model....

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1 National Geodetic Survey, Retrieval Date = DECEMBER 15, 2010JV6109 ***********************************************************************JV6109 HT_MOD - This is a Height Modernization Survey Station.JV6109 DESIGNATION - FOSTERJV6109 PID - JV6109JV6109 STATE/COUNTY- MD/BALTIMOREJV6109 USGS QUAD - HEREFORD (1974)JV6109JV6109 *CURRENT SURVEY CONTROLJV6109 ___________________________________________________________________JV6109* NAD 83(2007)- 39 34 44.11413(N) 076 42 48.20871(W) ADJUSTED

NGS Datasheet – GNSS NGS58/59

JV6109* NAVD 88 - 214.66 (meters) 704.3 (feet) GPS OBS JV6109 ___________________________________________________________________JV6109 EPOCH DATE - 2002.00JV6109 X - 1,131,361.846 (meters) COMPJV6109 Y - -4,790,998.768 (meters) COMPJV6109 Z - 4,042,177.076 (meters) COMPJV6109 LAPLACE CORR- -2.70 (seconds) DEFLEC09JV6109 ELLIP HEIGHT- 182.459 (meters) (02/10/07) ADJUSTEDJV6109 GEOID HEIGHT- -32.21 (meters) GEOID09JV6109

JV6109.The orthometric height was determined by GPS observations and aJV6109.high-resolution geoid model using precise GPS observation andJV6109.processing techniques.




NAVD88 – Ellipsoid Ht + Geoid Ht = …1.568 + 32.802 - 35.269 = -0.899 USGG20091.568 + 32.802 - 34.340 = +0.030 GEOID091.568 + 32.802 - 34.304 = +0.066 GEOID031.568 + 32.802 - 34.325 = +0.045 GEOID99

How accurate is a GPS-derived Orthometric Height?

• Relative (local) accuracy in ellipsoid heights between adjacent points will be better than 2 cm, at 95% confidence level

• Network accuracy (relative to NSRS) in ellipsoid and orthometric heights will be better ellipsoid and orthometric heights will be better than 5 cm, at 95% confidence level

• Accuracy of orthometric height is dependent on

– accuracy of the NAVD 88 control

– accuracy of the geoid model

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In Search of the Geoid…

Dr. Dan Roman

Dr. Yan Wang

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

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• 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

LEVEL SURFACES AND ORTHOMETRIC HEIGHTS

Level Surfaces

PlumbLine

“Geoid”

P

MeanSea

WP

PO

Level Surface = Equipotential Surface (W)H (Orthometric Height) = Distance along plumb line (PO to P)

Ocean

Level WO

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High Resolution Geoid Models

• Start with gravity measurements

• Add Digital Elevation Data (Continental)

• Add a Global Earth Gravity Model (EGM96,

EGM08)

• Result – A purely Gravitational geoid model –

good for scientific applications

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NGS’ Two Geoid Models

• Gravitational model:

• is good for scientific applications

• does not provide relationship between GPS heights and NAVD 88between GPS heights and NAVD 88

• “Hybrid” model:

• starts with gravitational model

• uses GPS on bench marks to enable a fit to NAVD 88

GRACE Satellite Gravity

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

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

Earth’s Surface

hh

h hh

HH

HEllipsoid

Gravimetric vs. Hybrid Geoid surface

Note use of GPS on BMs

0.994 M in Atlantic City–1999 model

0.987 M in Atlantic City –2003 model

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

HH

H H

NNNNN

Ellipsoid

Hybrid Geoid

Gravimetric GeoidGeoid

N N NN N

0.929 M in Atlantic City –2009 model

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That was then….

• At the start of Height Mod NGS felt the Gravimetric geoid was adequate as the base for the Hybrid geoid . . .

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

use GNSS (CORS) to monitor changes in heightsuse GNSS (CORS) to monitor changes in heights• Better understanding of poor condition of vertical

network – which continues to degrade• Gravity holdings at NGS evaluated

Is NAVD 88 “Maintainable”?

• NAVD88 defined through leveling network

• Not practical to re-leveling the country – Estimate re-leveling NAVD 88 would cost up to $2.25 Billion– Does not include densifying poorly covered areas in Western

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

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

Bias in NAVD 88

Approximate level of geoid mismatch known to exist in the NAVD 88 zero surface

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NGS Gravity Holdings

• 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

Terrestrial gravity 20-100 km gravity gaps along coast

New Orleans

Ship gravity

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

• Airborne Gravity Snapshot• Absolute Gravity Tracking

Transition to the Future – Gravity for the Redefinition of the American Vertical Datum

• Absolute Gravity Tracking• Re-define the U.S. Vertical

Datum by 2018 (if fully funded)

• Target: 2 cm orthometric heights using GNSS and gravimetric geoid model

http:/www.ngs.noaa.gov/GRAV-D/

Building a Gravity Field

Long Wavelengths:(" 400 km)

GRACE Satellite+

Intermediate Wavelengths(500 km to 20 km)

Airborne Measurement

Surface Measurement

Short Wavelengths(< 200 km)

http://www.dpi.nsw.gov.au/minerals/geological/info/oaklands-basin

+

Airborne Program Development

• Build GRAV-D project team – Field crew for airborne and

terrestrial gravity data collection

– Geodesists for processing gGPS and gravity data

• Instrumentation– New and upgraded

gravimeters

28


• When fully operational, will survey 10 months of the year for 8 years; 100 flight hours/month

• Currently use aircraft available: NOAA and other partners


• Data Processing: Software Development– GPS data processing

– Gravity data processingy p g

• Processing for QC on site

• Re-process with precise ephemerides in office

• Data management and archival

83

Newton 2.0

Airborne Data Flow

29

Current Status

20092010

20112011

Current Status

2009

2008

201020102011

2010

2011

2011

Priorities:

1. Finish Alaska2. Finish Gulf Coast3. Great Lakes4. East Coast5. West Coast6. Hawaii7. Pacific Island

H ldiHoldings8. Interior U.S.

30

Regional Partnerships & Collaborations

• Other Federal Agencies– USACE already funded Gulf of Mexico survey– NGA funded Alaska 2009 survey– USGS

• States– North Carolina, South Carolina

• Industry Partners: Micro-g LaCoste, Fugro• University Researchers

GRAV-D Web Page

• Program events are recorded here

• Survey progress ll b d l dwill be displayed

• Plan to make data and software available here

http://www.ngs.noaa.gov/grav-d

Table Mountain Geophysical Observatory (TMGO)

Before

• Develop long-term plan to measure/monitor gravity – goal to keep geoid accurate over time

• Renovate facility – add Office

After

• Renovate facility – add Office and meeting rooms for visiting scientists

• 11 gravity piers • Arrange international gravimeter

comparisons for calibration: first planned for Fall 2010

• Form international geoid steering committee

31

Geoid/GRAV-D TeamGEOID Team• Daniel R. Roman, Ph.D.• Yan Ming Wang, Ph.D.• Jarir Saleh• Simon Holmes, Ph.D.• Xiaopeng Li Ph D• Xiaopeng Li, Ph.D.

Aerogravity Collection/Processing• Vicki A. Childers, Ph.D.• Theresa Diehl, Ph.D.• Sandra A. Preaux

Programming/IT Support• William Waickman

• Access to accurate, reliable heights nationally

• Standards that are consistentacross the nation

Goal of NHMP

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

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

Consistency?

32

• Support NGS Mission for NSRS

• Needs don’t stop at state boundaries

• More efficient use of funds, people

• Encourages partnerships

A National ProgramThrough Regional Expansion

• Encourages partnerships

• Commitment by users and larger voice might result in increased Congressional support

• Difficult for state and local agencies to work outside of their mandates

National Height Modernization Program

Height Mod National Height Mod

Funding Source State earmarks Line item

Funding Recipients Grant Recipients NGS + Grant Recipients

Primary Driver 1998 Report to Congress

NGS 10 year plan +GRAV-D project plang GRAV D project plan

Geography 18 states All states and territories

Cost > $70 M $5(?)M / year, 10 years (split internal/external)

Dominant Activities Leveling, GPS, SRC’s, Outreach

Similar, plus airborne and terrestrial gravity, LIDAR, IFSAR

33

• Infrastructure

• Models and Tools

O t id C it B ildi

NGS Business Plan: 3 Areas of Focus

• Outside Capacity Building

• Two datums provided previously through the active (CORS) and passive (marks in the ground) networks will be redefined as “geometric” and “geopotential datums,”

Infrastructure – “Define, maintain, provide access to NSRS”

geometric and geopotential datums, accessed primarily through CORS

• Guidelines and standards will be updated for geodetic field and processing practices, keeping up with advanced surveying technologies

• Quality check data that is incorporated in the NGS database

• OPUS DB and Projects change how NGS

Infrastructure

accepts geodetic control into the NSRS

• Encourage use of active control over passive control, especially in dynamic areas

• Enable access to new datum through precise leveling when sub-cm relative heights needed

34

• Enable positioning consistent with NSRS – e.g. Real Time Networks

• Improve “timeliness” of coordinates on datasheets

R b /R dj t i l j t

Infrastructure

• Re-observe/Readjust – special case projects, gravity

• Model motion, develop tools – monitor with CORS, satellite gravity

• Metadata: Epochs, reliability scale, i.e. “Expiration date” on coordinates

Example: Louisiana

• Louisiana vertical control was out of date –subsidence

• Study of historic leveling data provided a crude model for updating heights

• Leveling/GPS/Gravity survey in 2004 provided up to date data – refine geoid model

• Publish new heights only; other heights ‘suppressed’

• Partnerships: FEMA, LSU/LSRC, NOAA, Parish Surveyors

• Collect new data – multi-faceted approach–Repeat GPS Surveys (2006, 2010)

Measure/Monitor Heights

–Densify CORS network–Observe relative & absolute gravity– Install new tide stations–Test Real Time Network (RTN)

35

Pre-2004

Estimate “subsidence” border

• 1 National Geodetic Survey, Retrieval Date = MARCH 18, 2009• BJ0196 ***********************************************************************• BJ0196 HT_MOD - This is a Height Modernization Survey Station.• BJ0196 FBN - This is a Federal Base Network Control Station.• BJ0196 DESIGNATION - E 284 X• BJ0196 PID - BJ0196• BJ0196 STATE/COUNTY- LA/ST LANDRY• BJ0196 USGS QUAD - BAYOU CURRENT (1994)• BJ0196• BJ0196 *CURRENT SURVEY CONTROL• BJ0196 ___________________________________________________________________• BJ0196* NAD 83(2007)- 30 46 55.32566(N) 091 46 23.63541(W) ADJUSTED

BJ0196* NAVD 88 11 54 ( t ) 37 9 (f t) GPS OBS

NGS Datasheet – GPS Height Mod

• BJ0196* NAVD 88 - 11.54 (meters) 37.9 (feet) GPS OBS • BJ0196 ___________________________________________________________________• BJ0196 EPOCH DATE - 2002.00• BJ0196 X - -169,707.673 (meters) COMP• BJ0196 Y - -5,481,757.847 (meters) COMP• BJ0196 Z - 3,245,148.124 (meters) COMP• BJ0196 LAPLACE CORR- 0.08 (seconds) DEFLEC99• BJ0196 ELLIP HEIGHT- -15.814 (meters) (02/10/07) ADJUSTED• BJ0196 GEOID HEIGHT- -27.25 (meters) GEOID03• BJ0196• BJ0196 ------- Accuracy Estimates (at 95% Confidence Level in cm) --------• BJ0196 Type PID Designation North East Ellip• BJ0196 -------------------------------------------------------------------• BJ0196 NETWORK BJ0196 E 284 X 0.25 0.25 0.76• BJ0196 -------------------------------------------------------------------

H = h - N11.54 = -15.814 - (- 27.25) 11.54 ! 11.436 (0.104 m/0.25 ft)

36

• 1 National Geodetic Survey, Retrieval Date = MARCH 17, 2009• AV0426 ***********************************************************************• AV0426 HT_MOD - This is a Louisiana Height Modernization Survey Station.• AV0426 DESIGNATION - D 215• AV0426 PID - AV0426• AV0426 STATE/COUNTY- LA/CAMERON• AV0426 USGS QUAD - CREOLE (1982)• AV0426• AV0426 *CURRENT SURVEY CONTROL• AV0426 ___________________________________________________________________• AV0426* NAD 83(2007)- 29 51 37.54827(N) 093 05 15.70510(W) ADJUSTED • AV0426* NAVD 88 - 0.65 (meters) 2.1 (feet) GPS OBS(2006.81)

AV0426 **Thi t ti i l t d i t d b id ( b l )

NGS Datasheet – Special 1

• AV0426 **This station is located in a suspected subsidence area (see below).• AV0426 **This station is included in the VTDP model (see below).• AV0426 ___________________________________________________________________• AV0426 EPOCH DATE - 2002.00• AV0426 X - -298,190.692 (meters) COMP• AV0426 Y - -5,527,916.711 (meters) COMP• AV0426 Z - 3,156,952.642 (meters) COMP• AV0426 LAPLACE CORR- 0.40 (seconds) DEFLEC99• AV0426 ELLIP HEIGHT- -26.050 (meters) (03/12/08) ADJUSTED• AV0426 GEOID HEIGHT- -26.76 (meters) GEOID03• AV0426• AV0426 ------- Accuracy Estimates (at 95% Confidence Level in cm) --------• AV0426 Type PID Designation North East Ellip• AV0426 -------------------------------------------------------------------• AV0426 NETWORK AV0426 D 215 0.96 0.82 2.00• AV0426 -------------------------------------------------------------------

• AV0426 ------- Accuracy Estimates (at 95% Confidence Level in cm) --------• AV0426 Type PID Designation North East Ellip• AV0426 -------------------------------------------------------------------• AV0426 NETWORK AV0426 D 215 0.96 0.82 2.00• AV0426 -------------------------------------------------------------------• AV0426 ELLP ORDER - THIRD CLASS I• AV0426• AV0426.The horizontal coordinates were established by GPS observations• AV0426.and adjusted by the National Geodetic Survey in February 2007.• AV0426• AV0426.The datum tag of NAD 83(2007) is equivalent to NAD 83(NSRS2007).• AV0426.See National Readjustment for more information.

AV0426 Th h i t l di t lid t th h d t di l d b


• AV0426.The horizontal coordinates are valid at the epoch date displayed above.• AV0426.The epoch date for horizontal control is a decimal equivalence• AV0426.of Year/Month/Day.• AV0426• AV0426.The orthometric height was determined by GPS observations and a• AV0426.high-resolution geoid model.• AV0426 ** Due to the variability of land subsidence, the orthometric, ellipsoid,• AV0426 ** and geoid heights are valid at the date of observation. These heights• AV0426 ** must always be validated when used as control.• AV0426 ** The orthometric height was determined with a Vertical Time-dependent• AV0426 ** Positioning (VTDP) model and has been validated through GPS observations• AV0426 ** for the epoch indicated (see www.ngs.noaa.gov/heightmod/VTDP.shtml).• AV0426 ** The geoid height was determined by a new realization of GEOID03 for the• AV0426 ** epoch indicated which incorporates improved geoid heights for the• AV0426 ** Southern Louisiana Subsidence area• AV0426 ** (see www.ngs.noaa.gov/PC_PROD/GEOID03).

• AV0421 ***********************************************************************• AV0421 HT_MOD - This is a Louisiana Height Modernization Survey Station.• AV0421 DESIGNATION - DRAWBRIDGE RESET• AV0421 PID - AV0421• AV0421 STATE/COUNTY- LA/CAMERON• AV0421 USGS QUAD - BOUDREAUX LAKE (1982)• AV0421• AV0421 *CURRENT SURVEY CONTROL• AV0421 ___________________________________________________________________• AV0421* NAD 83(2007)- 29 55 39.79753(N) 093 04 44.12719(W) ADJUSTED • AV0421* NAVD 88 - 2.31 (meters) 7.6 (feet) GPS OBS(2006.81)• AV0421 **This station is located in a suspected subsidence area (see below).

AV0421


• AV0421 ___________________________________________________________________• AV0421 EPOCH DATE - 2002.00• AV0421 X - -297,144.785 (meters) COMP• AV0421 Y - -5,524,251.283 (meters) COMP• AV0421 Z - 3,163,420.198 (meters) COMP• AV0421 LAPLACE CORR- 0.31 (seconds) DEFLEC99• AV0421 ELLIP HEIGHT- -24.540 (meters) (03/12/08) ADJUSTED• AV0421 GEOID HEIGHT- -26.90 (meters) GEOID03• AV0421 HORZ ORDER - A• AV0421 ELLP ORDER - THIRD CLASS I• AV0421• AV0421.The horizontal coordinates were established by GPS observations• AV0421.and adjusted by the National Geodetic Survey in March 2008.• AV0421

37

• BK2416 ***********************************************************************• BK2416 DESIGNATION - 28 A 032• BK2416 PID - BK2416• BK2416 STATE/COUNTY- LA/ST LANDRY• BK2416 USGS QUAD - SUNSET (1983)• BK2416• BK2416 *CURRENT SURVEY CONTROL• BK2416 ___________________________________________________________________• BK2416* NAD 83(1992)- 30 23 01.12137(N) 092 03 15.21777(W) ADJUSTED • BK2416* NAVD 88 - **(meters) **(feet) NOT PUB • BK2416 **This station is located in a suspected subsidence area (see below).• BK2416 ___________________________________________________________________

BK2416 LAPLACE CORR 0 40 ( d ) DEFLEC99


• BK2416 LAPLACE CORR- 0.40 (seconds) DEFLEC99• BK2416 GEOID HEIGHT- -27.45 (meters) GEOID03• BK2416 DYNAMIC HT - 14.510 (meters) 47.60 (feet) COMP• BK2416 MODELED GRAV- 979,322.9 (mgal) NAVD 88• BK2416• BK2416 HORZ ORDER - SECOND• BK2416 VERT ORDER - FIRST CLASS II• BK2416• BK2416.The horizontal coordinates were established by classical geodetic methods• BK2416.and adjusted by the National Geodetic Survey in January 1993.• BK2416• BK2416.The orthometric height was determined by differential leveling• BK2416.and adjusted in February 1994.• BK2416 ** Due to the variability of land subsidence, the orthometric, ellipsoid, …

• Assist USACE efforts to update datums on dams and levees

• Coordinate with FEMA during implementation of Map Modernization and Risk Map programs

Infrastructure – Current and planned activities

• Work with federal, state, university partners to target areas where infrastructure is deficient –develop strategy to enhance infrastructure so accurate transformation tools can be created

NOAA uses USGS Stream GagesUS Geological Survey (USGS) stream gages quickly provide

information used for emergency warnings as well as the long-term data needed to understand flood risks.

USGS Stream Gage at Pacific Creek near Moran,

WY

Issues!with!USGS!Stream!Gage!Data!:

Data!are!sometimes!not!referenced!to!the!official!national!vertical!datum

Gages can reference a localH(MLLW)

H (88)

H (29)

MHHW

Height Systems – Local Sea Level Heights and Geodetic

Vertical Datums

Gages!can!reference!a!local!datum!(even!if!decades!old)!ifthe!proper!conversion!is!used,!but a!conversion!may!not!be!readily!available

NAVD 88

NGVD 29

MHW

MTL

MLW

MLLW

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• Models

• Geoid: 1-cm; GRAV-D; strategy for monitoring

• HTDP: Partner with Scripps, UAF

• VTDP: Repeat surveys in Southern Louisiana, subsidence monitoring in Harris Galveston

Models/Tools – Current and planned

subsidence monitoring in Harris-Galveston Coastal Subsidence District

• Tools

• Online Geodetic tool kit

• LOCUS

• Tools

• Transformations: Vdatum – Use GPS and leveling to connect tidal and geodetic Datums for monitoring relative sea level change

• Field tools

Models/Tools – Current and planned

• PGM – Pocket GPS Manager (Scripps)

• Digital Elevation Tool (TX A&M)

• Develop standards and guidelines: use FGCS’ Vertical Reference System Work Group to reach out to stakeholders to evaluate needs

Leveling Spokane 2006

Outreach and Outside Capacity Building

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

Leveling – Spokane, 2006

• State Geodetic Advisor Program

• Forums, workshops

• Conferences

• Training, capacity building

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Height Modernization Partners

• Funded Partners– Academic Institutions– State and Local Governments– Spatial Reference Centers

• Offices within NOAA– National Weather Service– National Hurricane Center– Ocean and Atmosphere Research– National Ocean Service

• Other federal agencies– Department of Homeland Security/FEMA– US Army Corps of Engineers – e.g. levees, dams– US Geological Survey – e.g. stream gages

HM in Practice – What are states doing?• Infrastructure – establish, densify, maintain

– CORS – Passive control - leveling– Co-locate CORS and tide stations; level to tide stations– Remote sensing

• Models, tools– Pilot projects, test guidelinesPilot projects, test guidelines– Data collection, distribution - Gravity? – contribute to

models– Build state GIS– Develop software – PGM, “THM level tool”

• Outreach, education– Create Spatial Reference Centers– Workshops, forums, technology transfer– Websites, data access– NGS/State Geodetic Advisor Program

• Program Management

• Congressional briefings

• Budget, grants management

• Coordination – Partners, SRCs

• Project Leadership

• Develop National plan

• Support advance of science

• Support NOAA’s Mission – shoreline, weather, climate change

Prepare for Transition to new datums

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The NGS 10 year plan (2008-2018)

http://www.ngs.noaa.gov/INFO/NGS10yearplan.pdf

The GRAV-D Project

http://www ngs noaa gov/GRAV D

Additional Information

http://www.ngs.noaa.gov/GRAV-D

Socio-Economic Benefits of CORS and GRAV-D

http://www.ngs.noaa.gov/PUBS_LIB/Socio-EconomicBenefitsofCORSandGRAV-D.pdf

Full Report:http://www nap edu/catalog php?http://www.nap.edu/catalog.php?record_id=12954

From NGS’ 10-Year Plan

NGS Mission: “Modernize the Geopotential (“Vertical”) Datum”

“The gravimetric geoid, long used as the foundation for hybrid geoid models, becomes the most critical model produced by NGS.”

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Millstone River, Zaraphath, NJ-9/17/99, Post-Hurricane Floyd; photo Flood Mitigation Plan

ftp://ftp-fc.sc.egov.usda.gov/NJ/programs/watersheds/FranklinTwpFloodMitigationPlan.pdf

Winnie, Texas - September 14, 2008, Hurricane Ike (AP Photo/Pool, Smile N. Pool)

Hackensack River, Rivervale, NJ 4/16/07

http://nj.usgs.gov/hazards/flood/flood0407

Questions

Fast is fine, but accuracy is everything. – Wyatt Earp

A witty saying proves nothing. - Voltaire

Renee ShieldsHeight Modernization Manager301-713-3231, [email protected]

http://www.ngs.noaa.gov/heightmod/EventsArchive.shtml

NJSPLS Workshop Shields HeightModNJSPLSHandout · Differential Leveling – NAVD88: Accurate? ......

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