Orthometric Height (NAVD 88)

GPS-DERIVED HEIGHTS

PROFESSIONAL LAND SURVEYORS OF OREGON SALEM JANUARY 23, 2014

Dave Doyle Base 9 Geodetic Consulting Services National Geodetic Survey (Retired) [email protected]

ELLIPSOID - GEOID RELATIONSHIP

H = Orthometric Height (NAVD 88)

h = Ellipsoid Height (NAD 83 (2011)) N = Geoid Height (GEOID12A) H = h – N

H h N Geoid Geoid Model “Mean Sea Level” Ellipsoid GRS80 MONUMENTS IN THE GROUND ANTENNAS IN THE AIR HOW ARE ACCURATE HEIGHTS MEASURED?

LEVELING (mm accuracy) (very expensive, time consuming, highly trained personnel)

And/Or

GNSS (several cm accuracy) (cheaper, quicker, fewer trained personnel)

GEODETIC DATUMS

HORIZONTAL 2 D (Latitude and Longitude) (e.g. U.S. Standard Datum, NAD 27, NAD 83 (1986)) Fixed and Stable - Coordinates seldom change

GEOMETRIC 3-D (Latitude, Longitude and Ellipsoid Height) Fixed and Stable - Coordinates seldom change (e.g. NAD 83 (“HARN”), NAD 83 (CORS96), NAD 83 (2007), NAD 83 (2011))

4-D (Latitude, Longitude, Ellipsoid Height, Velocities) Coordinates change with time (e.g. ITRF00, IGS08)

VERTICAL 1 D (Orthometric Height) (Leveling constrained to 1 or more long-term tide stations) (e.g. NGVD 29, NAVD 88, PRVD 02, VIVD 09 etc.)

GEOPOTENTIAL 1 D (Orthometric Height) (Realized by GNSS + High Accuracy Gravimetric Geoid Model) (e.g. GRAV-D)

NATIONAL SPATIAL REFERENCE SYSTEM(NSRS)

Consistent National Coordinate System

• Latitude • Longitude • Height • Scale • Gravity • Orientation and how these values change with time NSRS COMPONENTS

• National Shoreline - Consistent, accurate, and up-to-date

• Networks of geodetic control points - Permanently marked passive survey monuments

• National and Cooperative CORS - A network of GPS Continuously Operating Reference Stations

• Tools -Models of geophysical effects on spatial measurements -e.g., NADCON, INVERSE, SPCS83, UTMS, FORWARD SUBSIDENCE: 10 MM/YEAR TO OVER 27 MM/YR WHEN WAS THE PASSIVE MARK ACCESSED? METADATA DATA ABOUT DATA

DATUMS

NAD 27, NAD 83(1986), NAD83 (1992), NAD 83 (2007), NAD 83 (2011), NGVD29, NAVD88

UNITS Meters, U.S. Survey Feet, International Feet

ACCURACY A-Order, B-Order, 1st, 2nd, 3rd, 3cm, .02 ft, Scaled GEOSPATIAL DATA REQUIRES METADATA! ON JUNE 20, THE M/V ZHEN HUA 13 DELIVERED NEW CRANES FROM CHINA TO THE PORT OF BALTIMORE BY NAVIGATING THE WATERS OF CHESAPEAKE BAY

Metadata Needed: - Local tidal datum reference - Tide info. - Channel bathymetry - Bridge dimensions - Bridge elevation- datum & accuracy - Ship squat - Crane height from keel - Water currents/ wave chop N E H PT 1,323922.832,2211566.199,398.638,HOLE 2,323910.487,2211572.158,398.101,MHSS 3,323993.852,2211224.037,428.904,MHSS 4,324077.107,2211089.654,444.897,MHSS 5,324077.559,2211098.749,444.796,PKNL 6,327586.448,2208838.501,383.945,DOT 7,327585.974,2208850.829,384.221,PIPE 8,327539.388,2209077.976,394.788,MONU 9,327530.076,2209127.079,396.808,MONU 10,327530.078,2209127.080,396.787,MONU

DATUM INFO Leica Smart Net North America Pennsylvania State Plane (South Zone) Horizontal-NAD 83 (2011) Vertical- NAVD 88 Observation Date-1/20/2014 TYPES OF HEIGHTS

ORTHOMETRIC The distance between the geoid and a point on the Earths surface measured along the plumb line. (From Leveling 0.1 – 2 cm / .003 – 0.06 ft)

GEOID The distance along a perpendicular from the ellipsoid of reference to the geoid (From Model 1-5 cm / .03 – .16 ft)

ELLIPSOID The distance along a perpendicular from the ellipsoid to a point on the Earth’s surface. (From GNSS Observations 1-5 cm / .03 – .16 ft)

VERTICAL DATUMS

A set of fundamental elevations to which other elevations are referred.

Datum Types

Tidal – Defined by observation of tidal variations over some period of time (MSL, MLLW, MLW, MHW, MHHW etc.)

Geodetic – Either directly or loosely based on Mean Sea Level at one or more points at some epoch (NGVD 29, NAVD 88, IGLD85 etc.)

IMPORTANCE OF SHORELINE

AL, AK, CA, CT, FL, GA, LA, MD, Territorial Seas MS, NJ, NY, NC, OR, RI, SC, WA Privately Owned State Owned Contiguous Zone Uplands Tidelands

Exclusive Economic Zone State Submerged Lands Federal Submerged Lands 3 n. mi. High Seas 12 n. mi. MHHW 200 n. mi. MHW

MLLW National Chart Datum

Privately State Owned Owned Privately State Owned Owned TX DE, MA, ME, NH, PA, VA

HEIGHT MODERNIZATION- USING GPS FOR HEIGHTS

Height Modernization -faster -cheaper -Nearly as good

differential leveling CHA – CHING $$$$$$$ ♪♪♪ GNSS Level Surfaces and Orthometric Heights

W Level Surfaces P

Plumb Line Local Mean Sea Level “Geoid” W

Ocean Level Surface = Equipotential Surface (W)

H (Orthometric Height) = Distance along plumb line (PO to P) LEVELED HEIGHT VS. ORTHOMETRIC HEIGHT

B Topography

∆ hAB = ∆ hBC A C

H A HC ∆HAC ≠ ∆hAB + ∆hBC

∆ h = local leveled differences ∆H = relative orthometric heights Observed difference in orthometric ∆ height, H, depends on the leveling route. 20 WHAT YOU CAN’T DO WITH GPS HEIGHTS

You cannot currently achieve orthometric heights to national standards, 1st, 2nd, or 3rd-Order with GPS observations GEODETIC LEVELING ACCURACY STANDARDS

CLASSIFICATION MAXIMUM ELEV. DIFFERENCE ACCURACY

FIRST - CLASS I 0.5 mm √Km

FIRST - CLASS II 0.7 mm √Km SECOND – CLASS I 1.0 mm √Km

SECOND – CLASS II 1.3 mm √Km

THIRD 2.0 mm √Km

(NOTE: REMEMBER THAT THERE ARE PROCEDURES AND EQUIPMENT SPECIFICATIONS TO FOLLOW FOR THESE CLASSES AS WELL) FEDERAL GEODETIC CONTROL SUBCOMMITTEE STANDARDS AND SPECIFICATIONS FOR GEODETIC CONTROL NETWORKS 1984 EXAMPLE

2nd- Order Class 2 = 1.3 mm x √ k For a 10 km / 6.2 mi line = 1.3 mm x √ 10 = 1.3 mm x 3.162 = 4 mm / 0.01 ft (95% confidence)

Macrometer V-1000 GPS Receiver 1982 ~ appox. $250,000 each Where are we now?? Global Positioning System

GPS Block I GPS Block II GPS Block III

. February 22, 1978 - 1st NAVSTAR Satellite launched . July 17, 1995 - System Fully Operational . May 1, 2000 - Selective Availability turned off . September 26, 2005 - L2C band added . May 28, 2010 - First L5 Satellite added . Mid 2014 – First Block III scheduled for launch . 2020? - 10-50 cm real-time accuracy! Global Navigation Satellite System

US - GPS Russia - GLONASS EU - Galileo China – BeiDou

Four positioning and navigation systems . NAVSTAR/GPS – US (Currently 31) . GLONASS – Russia (Currently 24) . GALILEO – EU (Currently 4, 30 by 2019) . BEIDOU – China (30+ by 2020?)

PRECISE ORTHOMETRIC HEIGHTS FROM GPS ARE MUCH HARDER TO ACHIEVE THAN HORIZONTAL POSITIONS

SOME REASONS:

 SATELLITE GEOMETRY LIMITED TO ZENITH ONLY

 ATMOSPHERIC EFFECTS ON THE GNSS SIGNAL CAUSE GREATER UNCERTAINTY IN THE VERTICAL

 ANTENNA PHASE CENTER VARIATION AFFECTS THE VERTICAL MORE

 BROADCAST/ ULTRA-RAPID/RAPID ORBITS IMPACT HEIGHTS MORE THAN HORIZONTAL

 ERRORS IN EACH COMPONENT OF THE: H = h – N ACCUMULATE GPS-DERIVED HEIGHTS RELY ON THREE ELEMENTS

1. GPS ELLIPSOID HEIGHT

2. A SOURCE OF ORTHOMETRIC HEIGHT TRUTH (PASSIVE MARKS FOR NAVD 88, ARPs FOR NAVD 22)

3. A MODEL TO PROVIDE A SEPARATION DISTANCE FROM THE REFERENCE ELLIPSOID TO THE “ELEVATION” DATUM SURFACE- CALLED A “GEOID HEIGHT”.

Z Zero GEODETIC DATUM= Meridian •SURFACE -X •ORIENTATION -Y - •SCALE •ORIGIN + GRAVITY

X Mean Equatorial Plane Y

-Z Earth-Centered Earth- Fixed Z (ECEF) XA, YA,ZA Coordinate System

Conventional Terrestrial Pole 1984.0 -Y Bureau International de l'Heure (BIH) -X now the IERS Earth Mass Center X, Y, Z = 0

X Y

-Z 3-D Coordinates derived from GPS

X1 Y1 X2 Z1 Y2 X3 Z2 Y3

X4 Y4 Z4

SPC/UTM Z

A XA φ A NA YA λA EA ZA hA hA Earth Mass Center +Z - Y A + Geoid Model +

- X Y φ A XA A NA Y X λ E Equator - Z A A HA HA FLAVORS OF OPUS

OPUS-S OPUS-PROJECTS $$ Receivers $$ Receivers 2 Hours of data 2-4 Hours of data Results not shared Multiple Receivers Network Solution Coming Soon ~ Fall ‘13 OPUS-RS $$ Receivers 15 Minutes of data Results not shared OPUS

OPUS-DB LOCUS (Leveling Online Computing User Service) $$ Receivers Digital Bar-Code Leveling 4 Hours of data Integration with GPS? Results shared Results shared or not? WHAT DOES OPUS OUTPUT LOOK LIKE? NGS OPUS SOLUTION REPORT ======

All computed coordinate accuracies are listed as peak-to-peak values. For additional information: http://www.ngs.noaa.gov/OPUS/about.jsp#accuracy

USER: [email protected] DATE: August 07, 2013 RINEX FILE: york212m.13o TIME: 21:25:23 UTC

SOFTWARE: page5 1209.04 master42.pl 072313 START: 2013/07/31 12:00:00 EPHEMERIS: igr17513.eph [rapid] STOP: 2013/07/31 14:00:00 NAV FILE: brdc2120.13n OBS USED: 5247 / 5463 : 96% ANT NAME: TRM33429.00+GP NONE # FIXED AMB: 42 / 42 : 100% ARP HEIGHT: 0.000 PUBLISHED OVERALL RMS: 0.015(m)

39 59 13.27663 - (0.006 m) REF FRAME: NAD_83(2011)(EPOCH:2010.0000) IGS08 (EPOCH:2013.5796) HOW GOOD ARE OPUS ORTHOMETRIC HEIGHTS? 76 X: 44 1122459.228(m)24.53717 0.010(m)- (0.002 m) 1122458.414(m) 0.010(m) Y: -4763243.010(m) 0.007(m) -4763241.571(m) 0.007(m) Z: 4076945.542(m) 99.616 m 0.007(m) - .000 4076945.479(m) 0.007(m)

LAT: 39 59 13.27644 IT 0.004(m) DEPENDS! 39 59 13.30795 0.004(m) E LON: 283 15 35.46292 0.012(m) 283 15 35.44343 0.012(m) W LON: 76 44 24.53708 0.012(m) 76 44 24.55657 0.012(m) EL HGT: 99.616(m) 0.007(m) 98.359(m) 0.007(m) ORTHO HGT:ORTHOMETRIC 133.337(m) 0.018(m) HEIGHT [NAVD88 (Computed ~ 0.02 using – GEOID12A)]0.04 m

UTM COORDINATES STATE PLANE COORDINATES GEOID12A ~ 0.04 UTM – (Zone 0.06 18) m (2 SPCsigma (3702 PA –S) 95% confidence) Northing (Y) [meters] 4427766.779 73075.174 Easting (X) [meters]Combined 351429.243 Errors 686248.814~ 0.03 + 0.05 Convergence [degrees] -1.11844862 0.65518429 Point Scale 0.99987174~ 0.08 m / 0.999992040.3 ft Combined Factor 0.99985611 0.99997641

US NATIONAL GRID DESIGNATOR: 18SUK5142927766(NAD 83)

BASE STATIONS USED PID DESIGNATION LATITUDE LONGITUDE DISTANCE(m) DL3184 LOYR LOYOLA R CORS ARP N393408.726 W0755914.994 79440.3 DM4139 PAFC CHAMBERSBURG CORS ARP N395649.413 W0774011.167 79546.7 DF6305 UMBC U OF MD BALT COOP CORS ARP N391524.360 W0764241.468 81116.0

NEAREST NGS PUBLISHED CONTROL POINT DE8103 YORK CORS ARP N395913.276 W0764424.537 0.0

This position and the above vector components were computed without any knowledge by the National Geodetic Survey regarding the equipment or field operating procedures used. RMS values (cm) along the n, e, and u components for each point and T OPUS Accuracy north east up

9.00 9.00 13.00

8.50 8.50 12.00 8.00 8.00

11.00 7.50 7.50 7.00 7.00 k=1; horizontal10.00 6.50 6.50 k 9.00 6.00 RMS() cm =6.00  5.50 5.50 8.00 GODE = GODE GODE 5.00 5.00 T k3.7; vertical MBW  7.00 MBW MBW W W W 4.50 MIA3 4.50 MIA3 MIA3 SLAI

centimeters SLAI 6.00 SLAI 4.00 centimeters 4.00 centimeters TCUN TCUN TCUN PRED 3.50 3.50 PRED 5.00 PRED

3.00 3.00 4.00 2.50 2.50

2.00 2.00 3.00

1.50 1.50 2.00

1.00 1.00 1.00 0.50 0.50

0.00 0.00 0.00 1 2 3 4 1 2 3 4 1 2 3 4

What is “THE” Geoid?

The equipotential surface of the Earth’s gravity field which best fits, in the least squares sense, global mean sea level Types and Uses of Geoid Height Models Gravimetric (or Gravity) Geoid Height Models (e.g. USGG2012, USGG2009) Defined by gravity data crossing the geoid Refined by terrain models (DEM’s) Scientific and engineering applications

Composite (or Hybrid) Geoid Height Models (e.g. GEOID12A, GEOID09) Starts with gravimetric geoid Warped to fit available GPSBM control data Defined by legislated ellipsoid (NAD 83) and local vertical datum (NAVD 88, PRVD02, etc.) May be statutory for some surveying & mapping applications Hybrid Geoid Models (e.g. GEOID12A), Gravimetric Geoid Model (e.g. USGG2012) and conversion surface using GPS on NAVD 88 Bench Marks in NSRS Earth’s Surface

h h h h h Ellipsoid H H H N H N H N N N

Hybrid Geoid 12A • 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 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) DISTRIBUTION OF GPSBM IN GEOID12A GEOID 12A Accuracy in Oregon Map Currently only available in DSWorld Comparison of 30 Minute Solutions - Precise Orbit; Hopfield (0); IONOFREE Two Days/Same Time (30 Minute solutions computed on the hour and the half hour) -10.254 > -10.253 MOLA to RV22 10.8 Km -10.251 Difference = 0.3 cm Day 264 * Mean dh * dh Hours dh minus diff Mean dh minus diff “Truth” = -10.276 Day 264 Day 265 (m) Diff. (m) Day 265 >2 (m) "Truth" >2 Difference = 2.3 cm (cm) cm (cm) cm

14:00-14:30 -10.281 27hrs 17:00-17:30 -10.279 -0.2 -10.280 -0.5 Two Days/ 14:30-15:00 -10.278 27hrs 17:30-18:00 -10.270 -0.8 -10.274 0.2 15:00-15:30 -10.281 27hrs 18:00-18:30 -10.278 -0.3 -10.280 -0.4 Different Times 15:30-16:00 -10.291 27hrs 18:30-19:00 -10.274 -1.7 -10.283 -0.7 -10.254 16:00-16:30 -10.274 27hrs 19:00-19:30 -10.274 0.0 -10.274 0.2 > -10.275 16:30-17:00 -10.287 27hrs 19:30-20:00 -10.276 -1.1 -10.282 -0.6 -10.295 17:00-17:30 -10.279 27hrs 20:00-20:30 -10.261 -1.8 -10.270 0.6 Difference = 4.1 cm 17:30-18:00 -10.270 27hrs 20:30-21:00 -10.251 -1.9 -10.261 1.5 18:00-18:30 -10.277 21hrs 15:00-15:30 -10.270 -0.7 -10.274 0.2 “Truth” = -10.276 18:30-19:00 -10.271 21hrs 15:30-16:00 -10.276 0.5 -10.274 0.2 19:00-19:30 -10.277 21hrs 16:00-16:30 -10.278 0.1 -10.278 -0.2 Difference = 0.1 cm 19:30-20:00 -10.271 21hrs 16:30-17:00 -10.286 1.5 -10.279 -0.3 20:00-20:30 -10.259 18hrs 14:00-14:30 -10.278 1.9 -10.269 0.7 20:30-21:00 -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 • UPDATED BY 8 YEARS (2002 T0 2010) • VELOCITIES BETTER KNOWN AT A MORE RECENT EPOCH • ABSOLUTE ANTENNA CALIBRATIONS (OLD = RELATIVE) • BASED ON IGS (2008) EPOCH 2005.0 [OLD WAS ITRF (2000) EPOCH 1997]

• 80,000 PASSIVE MARKS (FROM GPS CAMPAIGNS) • UPDATES POSITIONS BASED ON MULTI-YEAR CORS NAD 83 (2011) ADJUSTMENT • NAD 83 (2011) ELLIPSOID HEIGHTS ARE NOT COMPATIBLE WITH GEOID 09 • GEOID 12A DEVELOPED FOR USE WITH NAD 83 (2011) ELLIPSOID HEIGHTS AJ8186 *********************************************************************** AJ8186 DESIGNATION - LINDQUIST Identified as AJ8186 PID - AJ8186 AJ8186 STATE/COUNTY- OR/CLACKAMAS Height Mod AJ8186 COUNTRY - US AJ8186 USGS QUAD - BEDFORD POINT (1997) survey station AJ8186 AJ8186 *CURRENT SURVEY CONTROL AJ8186 ______AJ8186* NAD 83(2011) POSITION- 45 11 42.82165(N) 122 14 12.73862(W) ADJUSTED AJ8186* NAD 83(2011) ELLIP HT- 589.951 (meters) (06/27/12) ADJUSTED AJ8186* NAD 83(2011) EPOCH - 2010.00 AJ8186* NAVD 88 ORTHO HEIGHT - 612.2 (meters) 2009. (feet) GPS OBS AJ8186 ______AJ8186 NAVD 88 orthometric height was determined with geoid model GEOID99 AJ8186 GEOID HEIGHT - -22.20 (meters) GEOID99 AJ8186 GEOID HEIGHT - -22.21 (meters) GEOID12A AJ8186 NAD 83(2011) X - -2,401,800.839 (meters) COMP AJ8186 NAD 83(2011) Y - -3,808,557.337 (meters) COMP AJ8186 NAD 83(2011) Z - 4,503,082.514 (meters) COMP AJ8186 LAPLACE CORR - 2.72 (seconds) DEFLEC12A AJ8186 AJ8186 FGDC Geospatial Positioning Accuracy Standards (95% confidence, cm) AJ8186 Type Horiz Ellip Dist(km) AJ8186 ------AJ8186 NETWORK 0.87 2.43 AJ8186 ------AJ8186 MEDIAN LOCAL ACCURACY AND DIST (024 points) 1.08 2.99 39.53 AJ8186 ------AJ8186 NOTE: Click here for information on individual local accuracy AJ8186 values and other accuracy information. AJ8186 AJ8186 AJ8186.The horizontal coordinates were established by GPS observations AJ8186.and adjusted by the National Geodetic Survey in June 2012. AJ8186 AJ8186.NAD 83(2011) refers to NAD 83 coordinates where the reference AJ8186.frame has been affixed to the stable North American tectonic plate. See AJ8186.NA2011 for more information. AJ8186 AJ8186.The horizontal coordinates are valid at the epoch date displayed above AJ8186.which is a decimal equivalence of Year/Month/Day. AJ8186 AJ8186.The orthometric height was determined by GPS observations and a AJ8186.high-resolution geoid model. AJ8186 AJ8186.The ellipsoidal height was determined by GPS observations AJ8186.and is referenced to NAD 83. OPUS-DB POINT POSITIONING, BUT A REPLACEMENT FOR BLUEBOOKING

OPUS-DB ALLOWS USERS TO PUBLISH THEIR OPUS RESULT IN AN ON-LINE DATA BASE IF MINIMUM REQUIREMENTS FOR QUALITY ARE MET AND THE ASSOCIATED META-DATA, SUCH AS PHOTOS AND DESCRIPTIONS, ARE PROVIDED Available “On-Line” at NOAA Technical Memorandum NOS NGS-58 the NGS Web Site:

GUIDELINES FOR ESTABLISHING GPS-DERIVED ELLIPSOID HEIGHTS (STANDARDS: 2 CM AND 5 CM) www.ngs.noaa.gov VERSION 4.3

David B. Zilkoski Joseph D. D'Onofrio Stephen J. Frakes SEARCH: “NGS 58”

Silver Spring, MD

November 1997

U.S. DEPARTMENT OF National Oceanic and National Ocean National Geodetic COMMERCE Atmospheric Administration Service Survey Guidelines for Establishing GPS-Derived Orthometric Heights (Standards: 2 cm and 5 cm)

http://www.ngs.noaa.gov/ SEARCH: “NGS 59”

SOME FINAL THOUGHTS:

GEODETIC DIGITAL LEVELING IS STILL THE MOST PRECISE WAY TO PERFORM ORTHOMETRIC HEIGHT TRANSFERS.

NAVD 88 IS BASED UPON PHYSICAL BENCH MARKS THAT ESSENTIALLY HAVE UNKNOWN ACCURACY SINCE THE LAST TIME THEY WERE VERIFIED.

NAVD 88 CAN BE PROMULGATED USING GNSS TECHNOLOGY WITH VARYING ACCURACY THAT CAN APPROACH 3RD-ORDER GEODETIC LEVELING PRECISION. GOOD COORDINATION BEGINS WITH GOOD COORDINATES

GEOGRAPHY WITHOUT GEODESY IS A FELONY