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NATIONAL SPATIAL REFERENCE SYSTEM

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Title: NATIONAL SPATIAL REFERENCE SYSTEM


1
DEVELOPMENT, IMPLEMENTATION AND FUTURE OF THE
NATIONAL SPATIAL REFERENCE SYSTEM BRANSON,
MISSOURI SEPTEMBER 15, 2001 Don Mulcare National
Geodetic Survey Maryland Geodetic
Advisor Donald.Mulcare_at_noaa.gov, (410) 545-8963

2
Outline of Presentation
  • The figure of the Earth
  • Datums and Coordinate Systems
  • Horizontal and vertical
  • The Geoid
  • What is it? How is it calculated? How does it
    relate to other height surfaces?
  • Standards of Accuracy
  • Datum Transformations

3
Outline of Presentation
  • National Spatial Reference System
  • High Accuracy Reference Network
  • CORS
  • Accuracy in GIS
  • Development of local geodetic networks

4
ACRONYMS US
R
NAD 27
ITRF 97
GRS 80
WGS 84
NAVD 88
EGM 96
GEOID 99
NGVD 29
NAD 83
GEOID 96
5
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) - http//www.fgdc.gov/nsdi/
    nsdi.html 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

6
METADATA
  • METADATA IS DATA ABOUT DATA
  • DATUMS
  • NAD 27, NAD 83(1986), NAD83 (199X), NGVD29,
    NAVD88
  • UNITS
  • Meters, U.S. Survey Feet, International Feet,
    Chains, Rods, Pole
  • ACCURACY
  • A, B, 1st, 2nd, 3rd, 3cm, Scaled

7
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
    Service, International
  • GPS Service etc.)

8
THE MARK IS ON THE TOPO MAPBUT NOT IN THE NGS
DATA BASE??
Many of the monuments on the U.S. Geological
Survey (USGS) were set by USGS and other
agencies that were never submitted to NGS for
inclusion in NSRS Check bottom left corner of
topo for control by
9
THE ELLIPSOIDMATHEMATICAL MODEL OF THE EARTH
N
b
a
S
a Semi major axis b Semi minor axis f
a-b Flattening a
10
ELLIPSOID - GEOID RELATIONSHIP
H Orthometric Height (NAVD 88)
h Ellipsoidal Height (NAD 83)
H h - N
N Geoid Height (GEOID 99)

H
TOPOGRAPHIC SURFACE
h
N
GEOID99
Ellipsoid GRS80
Geoid
PERPENDICULAR TO ELLIPSOID
PERPENDICULAR TO GEOID (PLUMBLINE)
DEFLECTION OF THE VERTICAL
DEFLEC99
11
UNITED STATESELLIPSOID DEFINITIONS
BESSEL 1841 a 6,377,397.155 m 1/f
299.1528128
CLARKE 1866 a 6,378,206.4 m 1/f
294.97869821
GEODETIC REFERENCE SYSTEM 1980 - (GRS 80) a
6,378,137 m 1/f 298.257222101
WORLD GEODETIC SYSTEM 1984 - (WGS 84) a
6,378,137 m 1/f 298.257223563
12
GLOBALELLIPSOID DEFINITIONS
13
HORIZONTAL DATUMS
  • BESSEL 1841 -------------- LOCAL ASTRO DATUMS
    (1816-1879)

  • NEW ENGLAND DATUM (1879-1901)

  • U.S. STANDARD DATUM (1901-1913)

  • NORTH AMERICAN DATUM (1913-1927)

  • NORTH AMERICAN DATUM OF 1927
  • OLD
    HAWAIIAN DATUM
  • CLARKE 1866 PUERTO RICO DATUM

  • ST. GEORGE ISLAND - ALASKA

  • ST. LAWRENCE ISLAND - ALASKA

  • ST. PAUL ISLAND - ALASKA

  • AMERICAN SAMOA 1962

  • GUAM 1963
  • GRS80 ----------- NORTH AMERICAN DATUM OF
    1983

  • (As of June 14, 1989)

14
WORLD GEODETIC SYSTEM 1984TR8350.2 World
Geodetic System 1984 - Its Deinition
andRelationships with Local Geodetic
Systems(http//www.nima.mil/GandG/pubs.html)
DATUM WGS 84 RELEASED - SEPTEMBER 1987 BASED ON
OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS
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 285-292)
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 841-850)
15
MY SOFTWARE SAYS IM WORKING IN WGS-84
Unless you doing autonomous positioning (point
positioning /- 6-10 meters) youre probably NOT
in WGS-84
Project tied to WGS-84 control points obtained
from the Defense Department -- Good Luck!
Youre really working in the same reference frame
as your control points -- NAD 83?
16
I NEED TO TRANSFORMBETWEEN WGS 84 AND NAD 83
Federal Register Notice Vol. 60, No. 157, August
15, 1995, pg. 42146 Use of NAD 83/WGS 84 Datum
Tag on Mapping Products
17
THE GEOID AND TWO ELLIPSOIDS

CLARKE 1866
GRS80-WGS84
Earth Mass Center
Approximately 236 meters
GEOID
18
COMPARISON OF DATUM ELEMENTS

  • NAD 27 NAD 83
  • ELLIPSOID CLARKE 1866 GRS80
  • a 6,378,206.4 m
    a 6,378,137. M
  • 1/f 294.9786982
    1/f 298.257222101
  • DATUM POINT Triangulation
    Station
    NONE
  • MEADES RANCH, KANSAS EARTH MASS
    CENTER
  • ADJUSTMENT 25k
    STATIONS 250k STATIONS
  • Several Hundred Base Lines
    Appox. 30k EDMI Base Lines
  • Several Hundred Astro Azimuths
    5k Astro Azimuths

  • Doppler Point Positions

  • VLBI Vectors
  • BEST FITTING North
    America
    World-Wide

19
NAD 27 and NAD 83
20
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)

21
COMPARISON OF VERTICAL DATUM ELEMENTS

  • NGVD 29
    NAVD 88
  • DATUM DEFINITION 26 TIDE GAUGES
    FATHERS POINT/RIMOUSKI

  • IN THE U.S. CANADA
    QUEBEC, CANADA
  • BENCH MARKS 100,000
    450,000
  • LEVELING (Km)
    102,724
    1,001,500
  • GEOID FITTING Distorted to Fit
    MSL Gauges Best Continental
    Model

22
NGVD 29 and NAVD 88
23
GEOID MODELS
  • U.S. NATIONAL MODEL -- GEOID99 (http//www.ngs.noa
    a.gov/cgi-bin/GEOID_STUFF/geoid99_prompt1.prl)
  • CANADIAN NATIONAL MODEL -- GSD95
  • http//www.geod.nrcan.gc.ca/products/html-public/G
    SDinfo/English/factsheets/gpsht_fact.html
  • GLOBAL MODEL -- EGM 96
  • (http//WWW.NIma.mil/GandG/wgs-84/egm96.html)

24
(No Transcript)
25
Standalone Positioning Since May 1, 2000
6-11 m
  • C/A Code on L1
  • No Selective Availability

26
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

27
GLOBAL POSITIONING SYSTEM
  • GPS BLOCK III
  • Potential Future Developments
  • http//206.65.196.30/gps/issues/dotgpspressrelease
    s.htm
  • 30 - 32 satellites
  • Second and Third Civil Frequency
  • (1227.60 MHZ 1176.45 MHZ)
  • More Robust Signal Transmissions
  • Real-Time Unaugmented 1 Meter Accuracy
  • Initial Launches 2005
  • Complete Replacements 2011

28
GLOBAL NAVIGATION SATELLITE SYSTEMS(GNSS)
  • POTENTIAL FUTURE DEVELOPMENTS
  • (2005 - 2011)
  • US GPS MODERNIZATION - BLOCK III
  • RUSSIAN GLONASS ENHANCEMENTS
  • EUROPEAN UNION - GALILEO
  • 60 Satellites
  • Second and Third Civil Frequency - GPS
  • No Signal Encryption - GLONASS GALILEO
  • More Robust Signal Transmissions
  • Real-Time Unaugmented 1 Meter (or better!)
    Accuracy

29
INTERNATIONAL TERRESTRIALREFERENCE SYSTEM
DEVELOPED AND MAINTAINED BY THE INTERNATIONAL
EARTH ROTATION SERVICE PARIS, FRANCE
FROM (http//hpiers.obspm.fr/) VERY LONG
BASELINE INTERFEROMETRY - (VLBI) SATELLITE LASER
RANGING - (SLR) GLOBAL POSITIONING SYSTEM -
(GPS) DOPPLER ORBITOGRAPHY AND RADIO POSITIONING
INTEGRATED BY SATELLITE - (DORIS)
30
INTERNATIONAL TERRESTRIALREFERENCE SYSTEM
  • GEOCENTRIC /- 3 to 4 CM
  • MODELS FOR PLATE TECTONICS
  • STATION VELOCITIES
  • POSITIONAL STANDARD ERRORS
  • REALIZED AS THE INTERNATIONAL TERRESTERIAL
    REFERENCE FRAME (ITRF)

31
TECTONIC MOTIONS
32
HORIZONTAL TECTONIC MOTIONS
33
VERTICAL TECTONIC MOTIONS
34
NAD 83 and ITRF / WGS 84

NAD 83
ITRF / WGS 84
Earth Mass Center
2.2 m (3-D) dX,dY,dZ
GEOID
35
GEODETIC CONTROL
  • NETWORK OF MONUMENTED POINTS
  • PRECISELY MEASURED IN ACCORDANCE
  • WITH STANDARD PROCEDURES
  • MEET ACCURACY SPECIFICATIONS
  • ADJUSTED TO TIE TOGETHER
  • DOCUMENTED FOR MULTIPLE USE

36
Stainless steel rod driven to refusal
Poured in place concrete post
37
IMPROVING POSITIONAL ACCURACY
  • TIME NETWORK
    LOCAL
  • NETWORK SPAN ACCURACY ACCURACY
  • NAD 27 1927-1986
    10 Meters First-Order (1 part
    in 0.1 million)

  • NAD 83 1986-1990
    1 Meter First-Order(1
    part in 0.1 million)
  • HARN 1987-1997
    0.1 Meter B-Order(1
    part in 1 million)


  • A-Order (1 part in 10 million)
  • CORS 1994 -
    0.02 Meter -
    Horizontal

  • 0.04
    Meter - Ellipsoid Height


38
GEODETIC DATA SHEET
National Geodetic Survey, Retrieval Date
AUGUST 16, 2001 HC0880

HC0880 DESIGNATION - EDGAR HC0880 PID
- HC0880 HC0880 STATE/COUNTY- MO/PHELPS
HC0880 USGS QUAD - EDGAR SPRINGS (1954)
HC0880 HC0880 CURRENT
SURVEY CONTROL HC0880 __________________________
_________________________________________
HC0880 NAD 83(1997)- 37 42 25.66456(N) 091
52 01.53003(W) ADJUSTED HC0880 NAVD 88
- 370.943 (meters) 1217.00 (feet)
ADJUSTED HC0880 ______________________________
_____________________________________ HC0880 X
- -164,620.928 (meters)
COMP HC0880 Y - -5,049,963.870
(meters) COMP HC0880 Z
- 3,879,985.449 (meters)
COMP HC0880 LAPLACE CORR- 1.45
(seconds) DEFLEC99 HC0880
ELLIP HEIGHT- 340.49 (meters)
GPS OBS HC0880 GEOID HEIGHT-
-30.46 (meters) GEOID99
HC0880 DYNAMIC HT - 370.656 (meters)
1216.06 (feet) COMP HC0880 MODELED GRAV-
979,846.5 (mgal) NAVD 88
HC0880 HC0880 HORZ ORDER - B HC0880 VERT
ORDER - SECOND CLASS II HC0880 ELLP ORDER
- FOURTH CLASS I
H h - N 1217.00 1117.09
- (- 99.93) 1217.00 1217.02
39
GEODETIC DATA SHEET
  • HC0880.The horizontal coordinates were
    established by GPS observations
  • HC0880.and adjusted by the National Geodetic
    Survey in July 2001.
  • HC0880
  • HC0880.The orthometric height was determined by
    differential leveling
  • HC0880.and adjusted by the National Geodetic
    Survey in August 2001.
  • HC0880
  • HC0880.Photographs are available for this
    station.
  • HC0880
  • HC0880.The X, Y, and Z were computed from the
    position and the ellipsoidal ht.
  • HC0880
  • HC0880.The Laplace correction was computed from
    DEFLEC99 derived deflections.
  • HC0880
  • HC0880.The ellipsoidal height was determined by
    GPS observations
  • HC0880.and is referenced to NAD 83.
  • HC0880
  • HC0880.The geoid height was determined by
    GEOID99.
  • HC0880
  • HC0880.The dynamic height is computed by
    dividing the NAVD 88
  • HC0880.geopotential number by the normal gravity
    value computed on the



40
GEODETIC DATA SHEET


41
GEODETIC DATA SHEET
HC0880 North East
Units Scale Converg. HC0880SPC MO C
- 208,116.088 555,806.812 MT 0.99997168 0
23 13.6 HC0880SPC MO E - 208,807.252
129,454.145 MT 1.00011226 -0 50 10.5
HC0880UTM 15 - 4,173,925.084 599,862.246
MT 0.99972283 0 41 34.7 HC0880 HC0880
Primary Azimuth Mark
Grid Az HC0880SPC MO C - EDGAR AZ MK
349 43 42.7 HC0880SPC
MO E - EDGAR AZ MK
350 57 06.8 HC0880UTM 15 - EDGAR AZ
MK 349 25 21.6
HC0880 HC0880-----------------------------------
---------------------------------- HC0880 PID
Reference Object Distance
Geod. Az HC0880
dddmmss.s
HC0880 AJ3109 EDGAR RM 1
45.836 METERS 24509 HC0880 AJ3108 EDGAR
RM 2 41.437 METERS
31547 HC0880 AJ3110 CENSUS 2000
115.091 METERS 33237 HC0880
HC1101 EDGAR AZ MK
3500656.3 HC0880----------------------
-----------------------------------------------
HC0880 HC0880
SUPERSEDED SURVEY CONTROL HC0880 HC0880 NAD
83(1997)- 37 42 25.66376(N) 091 52
01.52851(W) AD( ) 2 HC0880 NAD 83(1986)-
37 42 25.67760(N) 091 52 01.52563(W) AD(
) 2 HC0880 NAD 27 - 37 42 25.53000(N)
091 52 00.96200(W) AD( ) 2 HC0880
HC0880.Superseded values are not recommended for
survey control. HC0880.NGS no longer adjusts
projects to the NAD 27 or NGVD 29 datums.

42
GEODETIC DATA SHEET
HC0880_MARKER DS TRIANGULATION STATION DISK
HC0880_SETTING 7 SET IN TOP OF CONCRETE
MONUMENT HC0880_STAMPING EDGAR 1947
HC0880_MARK LOGO CGS HC0880_MAGNETIC N NO
MAGNETIC MATERIAL HC0880_STABILITY C MAY
HOLD, BUT OF TYPE COMMONLY SUBJECT TO
HC0880STABILITY SURFACE MOTION HC0880 HC0880
HISTORY - Date Condition Report
By HC0880 HISTORY - 1947 MONUMENTED
CGS HC0880 HISTORY - 20010501 GOOD
NGS HC0880 HC0880
STATION DESCRIPTION HC0880 HC0880'DESCRIBED BY
COAST AND GEODETIC SURVEY 1947 (FRG)
HC0880'STATION IS LOCATED ABOUT 0.3 MILE NORTH OF
THE POST OFFICE IN HC0880'EDGAR SPRINGS, NEAR A
STANDARD SERVICE FILLING STATION AND ABOUT
HC0880'100 FT. EAST OF U.S. HIGHWAY NO 63. IT IS
108 FT. EAST OF THE HC0880'APPROXIMATE CENTER
LINE OF U.S. HIGHWAY NO 63, 73.8 FT. NORTH
HC0880'OF THE NORTHWEST CORNER OF THE FILLING
STATION BUILDING, 15.3 HC0880'FT. SOUTH OF A
FENCE AND 14.8 FT. SOUTH OF A WHITE WITNESS
POST. HC0880'THE MARK IS FLUSH WITH THE GROUND
AND THE DISK IS STAMPED HC0880'EDGAR 1947.
HC0880' HC0880'REFERENCE MARK NO 1 IS 150.38 FT.
WEST OF THE STATION, 42 FT. HC0880'WEST OF THE
APPROXIMATE CENTER LINE OF U.S. HIGHWAY NO 63,
17.6 HC0880'FT. NORTH OF A CORNER POST, 0.9 FT.
EAST OF A FENCE AND 3.3

43
HIGH ACCURACY REFERENCE NETWORKS
  • GPSABLE
  • Clear Horizons for Satellite Signal Acquisition
  • EASY ACCESSIBILITY
  • Few Special Vehicle or Property Entrance
    Requirements
  • REGULARLY SPACED
  • Always within 20-100 Km
  • HIGH HORIZONTAL ACCURACY
  • A-Order (5 mm 110,000,000)
  • B-Order (8mm 11,000,000)

44
HIGH ACCURACY REFERENCE NETWORKS
45
HIGH ACCURACY REFERENCE NETWORK
46
NAD 83 READJUSTMENT
  • HARN COMPLETION - SEPTEMBER 1997
  • (Indiana)
  • GPS HEIGHT MODERNIZATION OBSERVATIONS
  • (1997 - 2003?)
  • (States must develop observation plan)
  • (http//www.ngs.noaa.gov/initiatives/height_modern
    ization.shtml)
  • COMPLETE GPS NAD 83 3-D ADJUSTMENT
  • (http//www.ngs.noaa.gov/initiatives/new_reference
    .shtml)
  • (2005?)
  • REMOVAL OF SMALL REGIONAL DISTORTIONS
  • (3 - 6 CM)
  • UNIFORM COORDINATE TAG
  • NAD 83 (NSRS)

47
HARN REOBSERVATIONNGS Responsibilities
  • Training Workshops
  • Planning Assistance
  • On-Site Coordinator
  • Loan of Special Equipment
  • Fixed Height Poles
  • Meterological Sensor
  • GPS Vector Processing
  • Network Adjustment
  • Publication of Results in NSRS
  • Archival of Results in NSRS
  • Preparation of Project Report

48
HARN REOBSERVATIONState Responsibilities
  • NGS encourages partnerships between Federal,
    State,
  • County, Municipal and private surveying agencies
    and companies
  • Anyone with appropriate GPS equipment can
    participate
  • Dual-Frequency full-wavelenght L1/L2 Receivers
  • Antennas calibrated by NGS -- (http//www.ngs.noaa
    .gov/ANTCAL/index.shtml)
  • Project Coordinator
  • Performs GPS observations

49
NAD 83 READJUSTMENT
50
NAD 83 READJUSTMENT
  • ONLY GPS DATA
  • CONTINUOUSLY OPERATING REFERENCE STATIONS
  • FEDERAL BASE NETWORK
  • COOPERATIVE BASE NETWORK
  • AIRPORT SURVEYS
  • USER DENSIFICATION NETWORK
  • SPECIAL SURVEYS

51
NETWORK READJUSTMENTS
  • NAD 83 data that is NOT part of NSRS must be
    readjusted by contractor/user with original
    observations

52
NEW STANDARDS FOR GEODETIC CONTROL
  • Two accuracy standards
  • (http//fgdc.er.usgs.gov/standards/status/swgstat.
    html)
  • 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

53
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?

54
DATUM TRANSFORMATIONS
  • 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

55
DATUM TRANSFORMATIONS
  • 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).

56
I NEED TO TRANSFORMBETWEEN NAD 27 AND WGS 84
57
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

58
NADCON
  • 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

59
NADCON
N 0.12344 8 -1.87842
N 0.12249 8 -1.88963
N 0.12423 8 -1.81246
N 0.12568 8 -1.83364
N 0.12449 8 -1.88905
N 0.12640 8 -1.85407
N 0.12499 8 -1.86543
60
COORDINATE COMPARISONNAD 27 to NAD 83(1986)
  • (http//www.nima.mil/GandG/pubs.html)
  • TR8350.2 World Geodetic System 1984 - Its
    Definition and
  • Relationship with Local Geodetic Systems
  • ADJUSTED vs. TRANSFORMED
  • Station EDGAR
  • LATITUDE
    LONGITUDE
  • 37-42-25.67760
    091-52-01.52563 - PUBLISHED
  • 37-42-25.84799
    091-52-01.54332 - MOLODENSKY

  • .17039 .01769

  • 5.253 m 0.433 m
  • THIS CORRESPONDS TO A POSITIONAL
  • DIFFERENCE OF 5.271 m (17.29 ft)

61
COORDINATE COMPARISON NAD 27 to NAD
83(1986)
  • NADCON
  • (ftp//ftp.ngs.noaa.gov/pub/pcsoft/nadcon/)
  • ADJUSTED vs. TRANSFORMED
  • Station EDGAR

  • LATITUDE LONGITUDE
  • 37-42-25.67760
    091-52-01.52563 - PUBLISHED
  • 37-42-25.68080
    091-52-01.52499 - NADCON

  • .00320 .00064

  • 0.099 m 0.016 m
  • THIS CORRESPONDS TO A POSITIONAL
  • DIFFERENCE OF 0.100 m (0.33 ft)

62
COORDINATE COMPARISON NAD 83 (1986) to
NAD 83(1997)
  • NADCON
  • ADJUSTED vs. TRANSFORMED
  • Station EDGAR

  • LATITUDE LONGITUDE
  • 37-42-25.66456
    091-52-01.53003 - PUBLISHED
  • 37-42-25.66415
    091-52-01.52823 - NADCON

  • .00041 .00180

  • 0.013 m 0.044 m
  • THIS CORRESPONDS TO A POSITIONAL
  • DIFFERENCE OF 0.046 m (0.15 ft)

63
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
64
CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)
  • Variety of Geodetic Quality Dual-Frequency
  • Antennas and Receivers
  • Allen-Osborne
  • (SNR 8000 SNR 12 ACT)
  • Ashtech
  • (Z XII3)
  • Leica
  • (SR9500 CRS1000)
  • Trimble
  • (4000SSE 4000SSI)

CHL1 - CAPE HENLOPEN, DE
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CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)
  • Some stations provide real-time code phase
    observations
  • 5 - 15 - 30 post-process carrier phase
    observations
  • Free access via Internet (RINEX-2 Format)
  • More than 225 Station National Network

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CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)
  • NGS PROVIDES
  • Reference Site Survey Monumentation
  • Horizontal and Vertical NSRS Connections
  • NAD 83, ITRF94, ITRF96, ITRF97 Coordinates
  • Network Data Collection - Hourly Daily
  • Daily 3D Network Integrity Adjustment
  • Public Data Distribution - Internet
  • (http//www.ngs.noaa.gov/CORS/cors-data.html)
  • 7 Year On-Line Data Holding

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CORS DATA SHEET
ITRF 97 CONWAY (CNWM), MISSOURI
Retrieved from NGS DataBase on 09/11/00 at
090944. _______________________________________
_____________________________________

Antenna Reference
Point(ARP) CONWAY CORS ARP
--------------------------------------
-------
PID AH9092



ITRF97 POSITION (EPOCH
1997.0)
Computed in July 2000 using every third day
of data through 1999. X
-238909.294 m latitude 37 31 22.20223 N
Y -5059509.157 m
longitude 092 42 12.56512 W
Z 3863793.290 m ellipsoid height
359.430 m

ITRF97 VELOCITY

Computed in July 2000 using every third day of
data through 1999. VX -0.0147
m/yr northward -0.0080 m/yr
VY -0.0096 m/yr eastward
-0.0142 m/yr VZ
-0.0022 m/yr upward 0.0068 m/yr

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CORS DATA SHEET
NAD 83 CONWAY (CNWM), MISSOURI
Retrieved from NGS DataBase on 09/11/00 at
091917. ______________________________________
______________________________________ NAD_83
POSITION (EPOCH 1997.0)
Transformed from ITRF97
(epoch 1997.0) position in July 2000.
X -238908.766 m latitude
37 31 22.17807 N Y
-5059510.561 m longitude 092 42 12.54095
W Z 3863793.408 m
ellipsoid height 360.594 m

NAD_83 VELOCITY

Transformed from ITRF97 velocity in
July 2000. VX
0.0010 m/yr northward -0.0034 m/yr
VY -0.0075 m/yr
eastward 0.0014 m/yr
VZ 0.0014 m/yr upward
0.0068 m/yr
_______________________________________________
_____________________________
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CORS DATA QUALITY
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CORS DATA QUALITY
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OPUSOnLine Processing User Service
http//www.ngs.noaa.gov/OPUS/
OPUS allows users to submit their GPS data files
in RINEX format to NGS, where the data will be
processed to determine a position using NGS
computers and software. Each RINEX file that is
submitted will be processed with respect to the
3 nearest National CORS sites. The position for
your data will be reported back to you via email
in both ITRF and NAD83coordinates as well as UTM
and SPC northing and easting.
OPUS is completely automatic and requires only a
minimal amount of information from the user.
1.The email address where you want the
results sent 2.The RINEX file that you
want to process (which you may select using the
browse feature) 3.The antenna type used
to collect this RINEX file (selected from a list
of calibrated GPS antennas) 4.The height
of the Antenna Reference Point (ARP) above the
monument or mark that you are positioning
5.As an option, you may also enter the state
plane coordinate code if you want SPC northing
and easting.
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WHY HIGH ACCURACY IS IMPORTANT TO A GIS
  • Realistic, useable representation of data for
    local government, facilities management, utility
    and other applications.
  • Large scale applications can be performed.
  • Maps and decision making data are reliable.
  • Data can be aligned and integrated easily.
  • Survey data and GPS data can be input directly.
  • High accuracy data saves money for many
    operations.

? 2000
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SPATIAL DATA ACCURACY ISSUES IN GIS
  • Spatial data accuracy is crucial to building
    useful GISs.
  • GIS builders and users must understand
  • the impact of data accuracy on GIS.
  • details of spatial data accuracy.
  • their spatial data accuracy needs.
  • Surveying and mapping professionals should
  • understand the accuracy needs of GIS users.
  • be involved in GIS data design and collection.

? 2000
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MISPERCEPTIONS ABOUT GIS DATA ACCURACY
  • Assumptions
  • It will take care of itself
  • Well work on it later.
  • The maps look good.
  • The maps look accurate.
  • We dont really need that much accuracy.
  • What we have is good enough.
  • Lets just load whatever data we can get.
  • Its too expensive.
  • Too little attention and understanding.

? 2000
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MISPERCEPTIONS ABOUT GIS DATA ACCURACY
  • We can establish or adjust accuracy by
  • Digital orthophotos and satellite imagery
  • Heads-up digitizing based on evidence
  • Rubber sheeting

? 2000
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MISPERCEPTIONS ABOUT GIS DATA ACCURACY
  • All thats needed is a resource grade GPS unit.
  • It will supply one foot accuracy.
  • The GPS data can be used to adjust the other
    data.
  • It can be used for survey control.
  • GPS accuracy.

? 2000
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CONSEQUENCES OF INADEQUATE SPATIAL DATA ACCURACY
IN GIS PROJECTS
  • Data mismatches, inconsistencies, lack of
    registration
  • Confusion
  • Battling basemaps
  • Wasted resources
  • Decisions based on bad data
  • Decisions based on in appropriate data
  • Lawsuits
  • Failed projects

? 2000
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GPS NETWORKS TO SUPPORT GIS
  • CLASSICAL
  • Lots of control points spaced at regular
    intervals
  • (1-3 miles)
  • 21st CENTURY
  • CORS and Monumentation as needed

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GPS NETWORKS TO SUPPORT GIS
  • OBSERVE TO NATIONAL STANDARDS
  • TIES TO CORS, HARN and LOCAL BMs
  • QUALITY MONUMENTATION

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GPS NETWORKS TO SUPPORT GIS CLASSICAL
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GPS NETWORKS TO SUPPORT GIS 21st CENTURY
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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
    theyre used

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21st Century 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

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GPS NETWORKS TO SUPPORT GIS
  • GPS SURVEY DATA
  • BLUE - BOOK SUBMISSION OF DATA FOR
  • INCLUSION IN NSRS
  • OR
  • DATA MAINTAINED AT THE LOCAL LEVEL

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GPS NETWORKS TO SUPPORT GISBLUE-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 (15 - 20)
  • SLIGHT INCREASE IN INITIAL DATA PROCESSING TIME

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GPS NETWORKS TO SUPPORT GISLOCAL 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

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