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 PO 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 Z3 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 X φ A A 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.