ACRONYMS US HPGN EGM 96 HARN R ITRF 00 GRS 80 CORS NSRS NAVD 88

DEVELOPMENT, IMPLEMENTATION AND FUTURE OF THE NATIONAL SPATIAL REFERENCE SYSTEM
HOUSTON DECEMBER 13, 2003 David Doyle Chief Geodetic Surveyor National Geodetic Survey (301)

ACRONYMS US HPGN EGM 96 HARN R ITRF 00 GRS 80 CORS NSRS NAVD 88
NAD 27 ITRF 00 GRS 80 WGS 84 NSRS CORS EGM 96 NAVD 88 HPGN NGVD 29 HARN NAD 83

NATIONAL GEODETIC SURVEY
INFORMATION CENTER (301) WEB SITE

GEODETIC CONTROL NETWORK OF MONUMENTED POINTS
PRECISELY MEASURED IN ACCORDANCE WITH STANDARD PROCEDURES MEET ACCURACY SPECIFICATIONS ADJUSTED TO TIE TOGETHER DOCUMENTED FOR MULTIPLE USE

Stainless steel rod driven to refusal Poured in place concrete post

CORS SITES

NATIONAL SPATIAL REFERENCE SYSTEM (http://www.ngs.noaa.gov)
The National Spatial Reference System (NSRS) is that component of the National Spatial Data Infrastructure (NSDI) - [ which contains all geodetic control contained in the National Geodetic Survey (NGS) Data Base. This includes: A, B, First, Second and Third-Order horizontal and vertical control, Geoid models such as GEOID 99, precise GPS orbits and Continuously Operating Reference Stations (CORS), and the National Shoreline as observed by NGS as well as data submitted by other Federal, State, and local agencies, Academic Institutions and the private sector

NATIONAL SPATIAL REFERENCE SYSTEM
ACCURATE -- cm accuracy on a global scale MULTIPURPOSE -- Supports Geodesy, Geophysics, Land Surveying, Navigation, Mapping, Charting and GIS activities ACTIVE -- Accessible through Continuously Operating Reference Stations (CORS) and derived products INTEGRATED -- Related to International services and standards (e.g. International Earth Rotation and Reference Systems Service, International GPS Service etc.)

METADATA METADATA IS DATA ABOUT DATA DATUMS UNITS ACCURACY
NAD 27, NAD 83(1986), NAD83 (199X), NGVD29, NAVD88 UNITS Meters, U.S. Survey Feet, International Feet, Vara, Toise, Chains, Rods, Poles, Links, Perchs, Smoots ACCURACY A, B, 1st, 2nd, 3rd, 3cm, Scaled

METADATA?? Horizontal Datum?? Plane Coordinate Zone ??
Units of Measure ?? How Accurate ??

Horizontal and Vertical Datums ??
METADATA?? Horizontal and Vertical Datums ?? How Accurate B-Order, 1st-Order, 2cm, 0.01 ft?? Plane Coordinate Zone ?? Units of Measure ??

THE ELLIPSOID MATHEMATICAL MODEL OF THE EARTH
N b a S a = Semi major axis b = Semi minor axis f = a-b = Flattening a

ELLIPSOID - GEOID RELATIONSHIP
H = Orthometric Height (NAVD 88) H = h - N h = Ellipsoidal Height (NAD 83) N = Geoid Height (GEOID 99) TOPOGRAPHIC SURFACE h H N GEOID99 Geoid Ellipsoid GRS80

UNITED STATES ELLIPSOID DEFINITIONS
BESSEL 1841 a = 6,377, m 1/f = CLARKE 1866 a = 6,378,206.4 m 1/f = There have been several different ellipsoids used for the horizontal datums of the United States. The Bessell 1841 ellipse was used from approximately 1845 until Clarke 1866, developed by the English Geodesist A. R. Clarke was adopted in 1879 following the completion of the great Transcontinential Arc of Triangulation as it most closely approximates the size and shape of North America. As part of the activity to complete the North American Datum of 1983 (NAD 83), In 1979, the National Geodetic Survey decieded to adopt the Geodetic Reference System 1980 (GRS 80) as recommended by the International Association of Geodesy, as it most closely reflects the size and shape of the entire globe. It should be noted that GRS80 is for all practical purposes, the same size and shape as the World Geodetic System of 1984 (WGS 84) ellipsoid used with the Global Positioning System (GPS). The small numerical differences in the flattening (1/f) amount to less than 0.1 millimeter from the most northern part of Alaska to the southern tip of Florida!! GEODETIC REFERENCE SYSTEM (GRS 80) a = 6,378,137 m /f = WORLD GEODETIC SYSTEM (WGS 84) a = 6,378,137 m /f =

HORIZONTAL DATUMS BESSEL LOCAL ASTRO DATUMS ( ) NEW ENGLAND DATUM ( ) U.S. STANDARD DATUM ( ) NORTH AMERICAN DATUM ( ) NORTH AMERICAN DATUM OF 1927 OLD HAWAIIAN DATUM CLARKE PUERTO RICO DATUM ST. GEORGE ISLAND - ALASKA ST. LAWRENCE ISLAND - ALASKA ST. PAUL ISLAND - ALASKA AMERICAN SAMOA 1962 GUAM 1963 GRS NORTH AMERICAN DATUM OF 1983 (As of June 14, 1989)

COMPARISON OF DATUM ELEMENTS
NAD NAD 83 ELLIPSOID CLARKE GRS80 a = 6,378,206.4 m a = 6,378,137. M 1/f = /f = DATUM POINT Triangulation Station NONE MEADES RANCH, KANSAS EARTH MASS CENTER ADJUSTMENT k STATIONS k STATIONS Several Hundred Base Lines Appox. 30k EDMI Base Lines Several Hundred Astro Azimuths k Astro Azimuths Doppler Point Positions VLBI Vectors BEST FITTING North America World-Wide

NAD 27 and NAD 83

POOR STATION ACCESSIBILITY
NAD 83 NETWORK PROBLEMS NOT “GPSABLE” POOR STATION ACCESSIBILITY IRREGULARLY SPACED POSITIONAL ACCURACY

HIGH ACCURACY REFERENCE NETWORKS
“GPSABLE” Clear Horizons for Satellite Signal Acquisition EASY ACCESSIBILITY Few Special Vehicle or Property Entrance Requirements REGULARLY SPACED Always within Km HIGH HORIZONTAL ACCURACY A-Order (5 mm + 1:10,000,000) B-Order (8mm + 1:1,000,000)

IMPROVING POSITIONAL ACCURACY
TIME NETWORK LOCAL NETWORK SPAN ACCURACY ACCURACY NAD Meters First-Order (1 part in 0.1 million) NAD Meter First-Order(1 part in 0.1 million) HPGN/HARN Meter B-Order(1 part in 1 million) A-Order (1 part in 10 million) CORS Meter - Horizontal 0.04 Meter - Ellipsoid Height

HIGH ACCURACY REFERENCE NETWORK

HIGH ACCURACY REFERENCE NETWORKS

TEXAS HARN

INTERNATIONAL TERRESTRIAL REFERENCE SYSTEM
DEVELOPED AND MAINTAINED BY THE INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEM SERVICE PARIS, FRANCE ( VERY LONG BASELINE INTERFEROMETRY - (VLBI) SATELLITE LASER RANGING - (SLR) GLOBAL POSITIONING SYSTEM - (GPS) DOPPLER ORBITOGRAPHY AND RADIO POSITIONING INTEGRATED BY SATELLITE - (DORIS)

INTERNATIONAL TERRESTRIAL REFERENCE SYSTEM
GEOCENTRIC +/- 3 to 4 CM MODELS FOR PLATE TECTONICS STATION VELOCITIES POSITIONAL STANDARD ERRORS REALIZED AS THE INTERNATIONAL TERRESTERIAL REFERENCE FRAME (ITRF)

HOW MANY WGS 84s HAVE THERE BEEN????
WORLD GEODETIC SYSTEM 1984 TR World Geodetic System It’s Definition and Relationships with Local Geodetic Systems ( DATUM = WGS 84(G730) 5 USAF GPS Tracking Stations 5 DMA Evaluation Stations Datum redefined with respect to the International Terrestrial Reference Frame of 1992 (ITRF92) +/- 20 cm in each component (Proceedings of the ION GPS-94 pgs ) HOW MANY WGS 84s HAVE THERE BEEN???? DATUM = WGS 84(G873) 5 USAF GPS Tracking Stations 7 NIMA Evaluation Stations Datum redefined with respect to the International Terrestrial Reference Frame of 1994 (ITRF94) +/- 10 cm in each component (Proceedings of the ION GPS-97 pgs ) DATUM = WGS 84(G1150) Datum redefined with respect to the International Terrestrial Reference Frame of 2000 (ITRF00) +/- 2 cm in each component (Proceedings of the ION GPS-02) DATUM = WGS 84 RELEASED - SEPTEMBER 1987 BASED ON OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS

MY SOFTWARE SAYS I’M WORKING IN WGS-84
Unless you doing autonomous positioning (point positioning +/ meters) you’re probably NOT in WGS-84 Project tied to WGS-84 control point obtained from the Defense Department -- Good Luck! -- You’re really working in the same reference frame as your control points -- NAD 83?

TRANSFORM BETWEEN WGS 84 & NAD 83
dX = m dY = m dZ = m

THE GEOID AND TWO ELLIPSOIDS
CLARKE 1866 GRS80-WGS84 Earth Mass Center Approximately 236 meters GEOID

TECTONIC MOTIONS

HORIZONTAL TECTONIC MOTIONS

VERTICAL TECTONIC MOTIONS

NAD 83 and ITRF / WGS 84 NAD 83 ITRF / WGS 84 GEOID Earth Mass Center
2.2 m (3-D) dX,dY,dZ GEOID

VERTICAL DATUMS MEAN SEA LEVEL DATUM OF 1929
NATIONAL GEODETIC VERTICAL DATUM OF 1929 (As of July 2, 1973) NORTH AMERICAN VERTICAL DATUM OF 1988 (As of June 24, 1993)

COMPARISON OF VERTICAL DATUM ELEMENTS
NGVD NAVD 88 DATUM DEFINITION TIDE GAUGES FATHER’S POINT/RIMOUSKI IN THE U.S. & CANADA QUEBEC, CANADA BENCH MARKS , ,000 LEVELING (Km) , ,001,500 GEOID FITTING Distorted to Fit MSL Gauges Best Continental Model

NGVD 29 and NAVD 88

MHHW Highest and Lowest Observed are not a tidal datum or a computation. The acronyms can be found in our reference Glossary Standard Method (MTL, MSL, Mn, DHQ & DLG are known): MLW= MTL-(0.5*Mn) MHW= MLW+Mn MLLW= MLW-DLQ MHHW= MHW-DHQ DTL= 0.5*(MHHW+MLLW) GT= MHHW-MLLW MRR Method (MTL, DTL, MSL, Mn & GT are known): MLLW= MLW-0.5*GT MHHW= MHW+GT DHQ= MHHW-MHW DLQ= MLW-MLLW GT is known as the spring or diurnal range depending on what coast it is on.

Datum’s Boundary Applications
Boundaries to talk about in order of graphic enhancements: #MLW #MHW A coastal home owner would have more land if living in CT compared to MA owners #MLLW (chart datum) #territorial sea related to MLLW (12 n. mi.) #exclusive economic zone related to MLLW (200 n. mi.)

NOS BENCHMARK LEVELING
NOS uses a double run method we basically hit each benchmark twice this way the mark is double checked for stability (a.k.a. closure). Once per year during annual inspection for primary and secondary or before installation and after removal for tertiary. We’re more interested in the vertical stability than the horizontal. **Go to PC’s to show how to find this on the net** Distances vary but usually several hundred meters.

CANADIAN NATIONAL MODEL -- GSD95
GEOID MODELS U.S. NATIONAL MODEL -- GEOID99 ( CANADIAN NATIONAL MODEL -- GSD95 GLOBAL MODEL -- EGM 96 (

NEW U.S. GEOID MODEL Release by January 2004
USGG2003 and GEOID03 USGG = U.S. Gravimetric Geoid GEOID03 = U.S. Hybrid Geoid In excess of 11,000 GPS on BMs (A, B, and 1st- Order GPS on 1st, 2nd and 3rd – Order NAVD 88 BMs) Possibly overall misfit will be about 2.9 cm.

Standalone Positioning: Since May 1, 2000
C/A Code on L1 No Selective Availability

Standalone Positioning: By 2011
Better resistance to interference 1-3 m C/A Code on L1 C/A Code on L2 New Code on L5

GLOBAL POSITIONING SYSTEM
GPS BLOCK III Potential Future Developments satellites Second and Third Civil Frequency ( MHZ & MHZ) More Robust Signal Transmissions Real-Time Unaugmented 1 Meter Accuracy Initial Launches ~ 2005 Complete Replacements ~ 2015??

GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS)
POTENTIAL FUTURE DEVELOPMENTS (2005 – 2015??) GPS MODERNIZATION - BLOCK III GLONASS ENHANCEMENTS EUROPEAN UNION - GALILEO Satellites Second and Third Civil Frequency - GPS No Signal Encryption - GLONASS & GALILEO More Robust Signal Transmissions Real-Time Unaugmented 1 Meter (or better!) Accuracy

GEODETIC DATA SHEET Geodetic Data Sheets

GEODETIC DATA SHEET

GEODETIC DATA SHEET National Geodetic Survey, Retrieval Date = NOVEMBER 15, 2003 BN0540 *********************************************************************** BN0540 FBN This is a Federal Base Network Control Station. BN0540 DESIGNATION - CHERRY BN0540 PID BN0540 BN0540 STATE/COUNTY- TX/GILLESPIE BN0540 USGS QUAD - CHERRY SPRING (1967) BN0540 BN *CURRENT SURVEY CONTROL BN0540 ___________________________________________________________________ BN0540* NAD 83(1993) (N) (W) ADJUSTED BN0540* NAVD (meters) (feet) ADJUSTED BN0540 X , (meters) COMP BN0540 Y ,433, (meters) COMP BN0540 Z ,218, (meters) COMP BN0540 LAPLACE CORR (seconds) DEFLEC99 BN0540 ELLIP HEIGHT (meters) (05/01/00) GPS OBS BN0540 GEOID HEIGHT (meters) GEOID99 BN0540 DYNAMIC HT (meters) (feet) COMP BN0540 MODELED GRAV , (mgal) NAVD 88 BN0540 HORZ ORDER - B BN0540 VERT ORDER - FIRST CLASS II BN0540 ELLP ORDER - THIRD CLASS I H = h - N = ( )  (EGM96 = m)

GEODETIC DATA SHEET BN0540.The horizontal coordinates were established by GPS observations BN0540.and adjusted by the National Geodetic Survey in May 1994. BN0540 BN0540.The orthometric height was determined by differential leveling BN0540.and adjusted by the National Geodetic Survey in June 1991. BN0540.The X, Y, and Z were computed from the position and the ellipsoidal ht. BN0540.The Laplace correction was computed from DEFLEC99 derived deflections. BN0540.The ellipsoidal height was determined by GPS observations BN0540.and is referenced to NAD 83. BN0540.The geoid height was determined by GEOID99. BN0540.The dynamic height is computed by dividing the NAVD 88 BN0540.geopotential number by the normal gravity value computed on the BN0540.Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 BN0540.degrees latitude (g = gals.). BN0540.The modeled gravity was interpolated from observed gravity values. BN0540; North East Units Scale Converg. BN0540;SPC TX C ,092, , MT BN0540;UTM ,373, , MT

GEODETIC DATA SHEET BN0540: Primary Azimuth Mark Grid Az
BN0540:SPC TX C CHERRY AZ MK BN0540:UTM CHERRY AZ MK BN0540 BN0540| | BN0540| PID Reference Object Distance Geod. Az | BN0540| dddmmss.s | BN0540| BN0541 CHERRY RM METERS | BN0540| CV4542 CHERRY RM METERS | BN0540| BN0539 CHERRY RM METERS | BN0540| BN0538 CHERRY AZ MK | BN0540| BN0722 LOYAL MTN MICROWE RADIO MAST APPROX. 9.3 KM | BN SUPERSEDED SURVEY CONTROL BN0540 ELLIP H (05/09/94) (m) GP( ) 4 2 BN0540 NAD 83(1986) (N) (W) AD( ) 3 BN0540 NAD (N) (W) AD( ) 3 BN0540 NAVD 88 (05/09/94) (m) (f) LEVELING 3 BN0540 NGVD 29 (10/23/89) (m) (f) LEVELING 3 BN0540.Superseded values are not recommended for survey control. BN0540.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. BN0540.See file dsdata.txt to determine how the superseded data were derived.

GEODETIC DATA SHEET BN0540_U.S. NATIONAL GRID SPATIAL ADDRESS: 14RMU (NAD 83) BN0540_MARKER: DS = TRIANGULATION STATION DISK BN0540_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT BN0540_STAMPING: CHERRY 1956 BN0540_MARK LOGO: CGS BN0540_PROJECTION: PROJECTING 12 CENTIMETERS BN0540_MAGNETIC: O = OTHER; SEE DESCRIPTION BN0540_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO BN0540+STABILITY: SURFACE MOTION BN0540_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR BN0540+SATELLITE: SATELLITE OBSERVATIONS - September 05, 2001 BN0540 BN0540 HISTORY Date Condition Report By BN0540 HISTORY MONUMENTED CGS BN0540 HISTORY GOOD CGS BN0540 HISTORY GOOD NGS BN0540 HISTORY GOOD NGS BN0540 HISTORY GOOD NGS BN0540 HISTORY GOOD USPSQD BN0540 HISTORY GOOD NGS BN0540 HISTORY GOOD INDIV BN STATION DESCRIPTION BN0540'DESCRIBED BY COAST AND GEODETIC SURVEY 1956 (WFD) BN0540'THE STATION IS 0.65 MILE NORTH OF CHERRY SPRINGS, 0.1 MILE BN0540'SOUTH OF THE GILLESPIE-MASON COUNTY LINE AND ON THE RIGHT-OF-WAY

GEODETIC CONTROL DATA SHEET
National Geodetic Survey, Retrieval Date = SEPTEMBER 11, 2003 TA0047 *********************************************************************** TA0047 DESIGNATION - G 216 TA0047 PID TA0047 TA0047 STATE/COUNTY- MN/COOK TA0047 USGS QUAD - LONG ISLAND LAKE (1986) TA0047 TA *CURRENT SURVEY CONTROL TA0047 ___________________________________________________________________ TA0047* NAD 83(1986) (N) (W) HD_HELD1 TA0047* NAVD (meters) (feet) ADJUSTED TA0047 GEOID HEIGHT (meters) GEOID99 TA0047 DYNAMIC HT (meters) (feet) COMP TA0047 MODELED GRAV , (mgal) NAVD 88 TA0047 VERT ORDER - SECOND CLASS 0 TA0047.The horizontal coordinates were established by differentially corrected TA0047.hand held GPS obs and have an estimated accuracy of +/- 3 meters. TA0047.The orthometric height was determined by differential leveling TA0047.and adjusted by the National Geodetic Survey in June 1991. TA0047.Photographs are available for this station. TA0047; North East Units Estimated Accuracy TA0047;SPC MN N , , MT (+/- 3 meters HH1 GPS) Up dated position by hand held GPS

NAD 83 READJUSTMENT NAD 83 READJUSTMENT ONLY GPS DATA
CONTINUOUSLY OPERATING REFERENCE STATIONS FEDERAL BASE NETWORK COOPERATIVE BASE NETWORK USER DENSIFICATION NETWORK LAYERED ADJUSTMENT OF 3,000 INDIVIDUAL PROJECTS INLCUDING MORE THAN 59,000 STATIONS BOTH NAD 83(NSRS) AND ITRF COORDINATES WILL BE PUBLISHED

NETWORK READJUSTMENTS
NAD 83 data that is NOT part of NSRS must be readjusted by contractor/user with original observations

NEW STANDARDS FOR GEODETIC CONTROL
Two accuracy standards ( local accuracy adjacent points network accuracy relative to CORS Numeric quantities, units in cm (or mm) Both are relative accuracy measures Do not use distance dependent expression Horizontal accuracies are radius of 2-D 95% error circle Ellipsoidal/Orthometric heights are 1-D (linear) 95% error

CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)
Installed and Operated by various Federal-State-local Agencies NOAA/National Geodetic Survey NOAA/OAR Forecast Systems Lab U.S. Coast Guard - DGPS/NDGPS Corps of Engineers - DGPS FAA - WAAS/LAAS (Future) State DOTs County and City Academia Private Companies CHL1 - CAPE HENLOPEN, DE

Variety of “Geodetic Quality” Dual-Frequency Antennas and Receivers Allen-Osborne Ashtech/Thales Leica Trimble CHL1 - CAPE HENLOPEN, DE

Some stations provide real-time code phase observations ” post-process carrier phase observations Free access via Internet (RINEX-2 Format) More than 425 Station National Network

NGS PROVIDES Reference Site Survey Monumentation Horizontal and Vertical NSRS Connections NAD 83, ITRF94, ITRF96, ITRF97, ITRF00 Coordinates Network Data Collection - Hourly & Daily Daily 3D Network Integrity Adjustment Public Data Distribution - Internet ( 9 Year On-Line Data Holding

CORS DATA QUALITY

IGS Tracking Network

On-line Positioning User Service
OPUS – WHAT IS IT? On-line Positioning User Service Provide GPS users faster & easier access to the National Spatial Reference System (NSRS)

OPUS – HOW DOES IT WORK? Submit RINEX file through NGS web page
Processed automatically with NGS computers & software With respect to 3 suitable or user-selected National CORS Solution via in minutes

OPUS – HOW DO I USE IT? Go to OPUS web page www.ngs.noaa.gov/OPUS
Enter your address Use browse feature to select RINEX file on your computer Select antenna type from menu Enter antenna height in meters Option to select State Plane Zone Click UPLOAD Check your in a few minutes

DATUM TRANSFORMATIONS
1. WHAT DATUM ARE THE EXISTING COORDINATES ON? 2. WHAT DATUM DO I WANT THE NEW COORDINATES ON? 3. HOW LARGE A GEOGRAPHICAL AREA DO I WANT TO CONVERT AT ONE TIME? 4. HOW MANY POINTS ARE COMMON TO BOTH DATUMS? 5. WHAT IS THE DISTRIBUTION OF THE COMMON POINTS? 6. HOW ACCURATE ARE THE EXISTING COORDINATES? 0.1 Foot 1.0 Foot 10. Feet 7. HOW ACCURATE DO I WANT THE NEW COORDINATES?

MOLODENSKY Converts latitude, longitude and ellipsoidal height to X,Y,Z Earth-Centered Coordinates. Applies a 3-dimensional change in the origin (dX, dY,dZ) Applies a change in the size and shape of the reference ellipsoid Converts new X,Y,Z Earth-Centered Coordinates back to latitude, longitude and ellipsoidal height

MOLODENSKY For continental regions accuracy can be +/- 8 to 10 meters Does not model network distortions very well. Assumes heights in both systems are ellipsoidal (NAD 27 did not have ellipsoidal heights).

Z Y X Greenwich Meridian Equator Earth-Centered Earth-Fixed (ECEF) A
Coordinate System (X,Y,Z,) A Latitude Longitude Ellipsoid Height Greenwich Meridian ZA Earth Mass Center - Y - X YA Y X XA Equator - Z

Z Y X Z X Y Earth-Centered Earth-Fixed (ECEF) A Coordinate System ZB
XB YB ZB Y X Z A XA YA ZA X Y

Z Z Y Z Y X X Y X 3 Parameter Molodensky Transformation
“In The Real World” X Z Y A XB YB ZB X Z Y A XB YB ZB X Z Y A XA YA ZA dZ dY dX

I NEED TO TRANSFORM BETWEEN NAD 27 AND WGS 84

MOLODENSKY TRANSFORMATION
COMPUTED vs. MODELED Station: CHERRY NAD NAD 83(1992) dX, dY,dZ X = , m X = , m m Y = - 5,433, m Y = - 5,433, m m Z = +3,218, m Z = + 3,218, m m COMPUTED NIMA EAST NIMA CONUS dX = - 9 m dX = -9 (0 m) dX = -8 (1m) dY = dY = (16 m) dY = (15 m) dZ = dZ = (2 m) dZ = (5 m)

DATUM TRANSFORMATION IDEAL METHOD
SATISFIES ALL USERS’ REQUIREMENTS CAPABLE OF TRANSFORMING LARGE HOLDINGS OF COORDINATE DATA NEAR-REAL TIME APPLICATIONS SIMPLE - METHOD SHOULD NOT REQUIRE AN EXPERT OR DECISIONS TO BE MADE ACCURATE

NADCON 5 cm (1 sigma) per State/Region NAD 83 (1986) - HARN
DESIGNED TO SATISFY THE MAJORITY OF THE “IDEAL METHOD” DESIGN AND HAS DEFINED AS THE NATIONAL STANDARD. DESIGN CRITERIA: Relies only on NGS archived data existing in both NAD 27 and NAD 83 Provides consistent results, both forward and inverse Fast Not tied to NGS Data Base Small - Fit on PC Accurate 15 cm (1 sigma) in Conterminous U.S. NAD 27 - NAD 83(1986) 5 cm (1 sigma) per State/Region NAD 83 (1986) - HARN

NADCON N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 = N = 8 =

COORDINATE TRANSFORMATION COMPARISON NAD 27 to NAD 83(1992)
MOLODENSKY ADJUSTED vs. TRANSFORMED Station: CHERRY LATITUDE LONGITUDE PUBLISHED MOLODENSKY .19910” ” 6.131 m m THIS CORRESPONDS TO A POSITIONAL DIFFERENCE OF m (21.52 ft)

COORDINATE TRANSFORMATION COMPARISON NAD 27 to NAD 83(1992)
NADCON (ftp://ftp.ngs.noaa.gov/pub/pcsoft/nadcon/) ADJUSTED vs. TRANSFORMED Station: CHERRY LATITUDE LONGITUDE PUBLISHED NADCON .00930” ” 0.286 m m THIS CORRESPONDS TO A POSITIONAL DIFFERENCE OF m (1.01 ft)

GPS NETWORKS TO SUPPORT GIS
“CLASSICAL” Lots of control points spaced at regular intervals (1-3 miles) “CONTEMPORARY” CORS and Monumentation as needed

OBSERVE TO NATIONAL STANDARDS TIES TO CORS, HARN and LOCAL BMs QUALITY MONUMENTATION

GPS NETWORKS TO SUPPORT GIS CLASSICAL

GPS NETWORKS TO SUPPORT GIS CONTEMPORARY

CLASSICAL GPS NETWORKS
PROS Monumentation usually established in only 1 or 2 GPS survey campaigns Complete coverage No time lag for users access to control CONS Large initial cost Continual network maintenance Monumentation destroyed or disturbed before they’re used

CONTEMPORARY GPS NETWORKS
PROS Minimal “permanent” monumentation Project control established when and where needed Costs spread over time CONS Qualified staff to coordinate user requirements Time lag to establish project control

GPS SURVEY DATA “BLUE - BOOK” SUBMISSION OF DATA FOR INCLUSION IN NSRS OR DATA MAINTAINED AT THE LOCAL LEVEL

GPS NETWORKS TO SUPPORT GIS “BLUE-BOOK”
PROS DATA MAINTAINED IN NSRS IN PERPETUTITY PROVIDES IMPROVED DATA FOR FUTURE NATIONAL GEOID MODELS UNIVERSAL DATA ACCESS VIA NGS WEB SITE “GOOD HOUSEKEEPING SEAL OF APPROVAL” CONS INCREASED INITIAL COST ( %) SLIGHT INCREASE IN INITIAL DATA PROCESSING TIME

GPS NETWORKS TO SUPPORT GIS LOCAL MAINTENANCE
PROS DECREASED INITIAL SURVEY COSTS LOCAL CONTROL OF ALL DATA CONS READJUSTMENTS TO FUTURE REFERENCE FRAME CHANGES MUST BE DONE AT THE LOCAL LEVEL DATA MAY BE DIFFICULT TO LOCATE FOR “NON-LOCALS” DATA DOES NOT CONTRIBUTE TO FUTURE NATIONAL GEOID MODELS

GOOD COORDINATION BEGINS WITH
GOOD COORDINATES GEOGRAPHY WITHOUT GEODESY IS A FELONY

ACRONYMS US HPGN EGM 96 HARN R ITRF 00 GRS 80 CORS NSRS NAVD 88

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ACRONYMS US HPGN EGM 96 HARN R ITRF 00 GRS 80 CORS NSRS NAVD 88

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