P1246990938TpdkC

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THE NORTH AMERICAN DATUM OF 1983 (NAD 83)
Alaska Surveying and Mapping Conference February
23, 2005 David Doyle Chief Geodetic
Surveyor National Geodetic Survey
dave.doyle_at_noaa.gov, [phone]
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NATIONAL SPATIAL REFERENCE SYSTEM

• 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
  Horizontal and Vertical Datums (e.g. NAD 27, NAD
  83, NGVD 29, NAVD 89 etc.), Geoid models such as
  GEOID 03, 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

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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.)

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WHAT IS A GEODETIC DATUM?

• A set of constants specifying the coordinate
  systems used for geodetic control, i.e., for
  calculating coordinates and elevations of points
  on the Earth. Specific geodetic datums are
  usually given distinctive names. (e.g., North
  American Datum of 1983, Guam 1963, National
  Geodetic Vertical Datum of 1929 etc.)
• Characterized by
• A set of physical monuments with
• published horizontal or vertical coordinates

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Geodetic Datums

• Classical
• Horizontal 2 D (Lat and Long, e.g. NAD 27, NAD
  83 (1986))
• Vertical 1 D (Orthometric Height, e.g. NAVD 88)
• Contemporary
• Practical 3 D (Latitude, Longitude and
  Ellipsoid Height) Fixed and Stable Coordinates
  seldom change, e.g. NAD 83 (1991)
• Scientific 4 D (Latitude, Longitude,
  Ellipsoid Height, Velocities) Coordinates
  change with time, e.g. ITRF00

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HORIZONTAL DATUMS

• 8 Constants
• 3 specify the location of the origin of the
  coordinate system.
• 3 specify the orientation of the coordinate
  system.
• 2 specify the dimensions of the reference
  ellipsoid

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GEODETIC REFERENCE SYSTEM

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

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Stainless steel rod driven to refusal
Poured in place concrete post
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Continuously Operating Reference Stations
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THE ELLIPSOIDA MATHEMATICAL MODEL OF THE EARTH
N
b
a
S
a Semi major axis b Semi minor axis f
a-b Flattening a
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ELLIPSOID - GEOID RELATIONSHIP
H Orthometric Height (NAVD 88)
H h - N
h Ellipsoidal Height (NAD 83)

N Geoid Height (GEOID 03)
H
h
N
GEOID 03
Geoid
Ellipsoid GRS80
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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
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Whats Wrong With NAD 27

• Best fitting to just North America
• Non Geocentric
• Significant scale and azimuth distortion
• Poorly determined relationship to the geoid

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NAD 83 PROJECT

• July 1, 1974 to July 31, 1986
• 4,997 Individual survey projects dating from 1817
  containing 266,436 stations
• 1,785,772 Observations
• Partnerships with Canada, Mexico and
  Interamerican Geodetic Survey

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US Navy Transit Satellite1964
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Navstar Global Positioning System (GPS) Satellite
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Very Long Baseline Interferometer
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NAD 83

• Official Horizontal Datum of the United States
  Federal Register Notice, Vol. 54 No. 113/
  Wednesday June 14, 1989.
• The interagency Federal Geodetic Control
  Committee (FGCC) affirmed NAD 83 is the official
  horizontal datum for U.S. surveying and mapping
  activities performed or financed the Federal
  Government. Furthermore, to the extent
  practicable, legally allowable and feasible, all
  Federal agencies using or producing coordinate
  information should provide for an orderly
  transition from NAD 27 to NAD 83.

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NAD 27 and NAD 83
ALASKA 110 m to 240 m
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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)
• HPGN/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
• 
  

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WORLD GEODETIC SYSTEM 1984TR8350.2 World
Geodetic System 1984 - Its Definition
andRelationships with Local Geodetic
Systems(http//earth-info.nima.mil/GandG/pubs.htm
l)
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(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)
http//164.214.2.59/GandG/sathtml/IONReport8-20-0
2.pdf
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 841-850)
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I NEED TO TRANSFORMBETWEEN WGS 84 AND NAD 83
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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?
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National Geodetic Survey, Retrieval Date
NOVEMBER 30, 2004 TT0815

TT0815 DESIGNATION - TT AN 7 TT0815 PID
- TT0815 TT0815 STATE/COUNTY- AK/ANCHORAGE
BOROUGH TT0815 USGS QUAD - ANCHORAGE A-8
TT0815 TT0815 CURRENT
SURVEY CONTROL TT0815 __________________________
_________________________________________
TT0815 NAD 83(1992)- 61 14 18.74244(N) 149
48 39.96942(W) ADJUSTED TT0815 NAVD 88
- 51.675 (meters) 169.54 (feet)
ADJUSTED TT0815 ______________________________
_____________________________________ TT0815 X
- -2,659,572.827 (meters)
COMP TT0815 Y - -1,547,218.487
(meters) COMP TT0815 Z
- 5,568,232.216 (meters)
COMP TT0815 LAPLACE CORR- 39.56
(seconds) DEFLEC99 TT0815
ELLIP HEIGHT- 58.69 (meters)
(09/01/92) GPS OBS TT0815 GEOID HEIGHT-
9.12 (meters) GEOID99
TT0815 DYNAMIC HT - 51.744 (meters)
169.76 (feet) COMP TT0815 MODELED GRAV-
981,927.3 (mgal) NAVD 88
TT0815 TT0815 HORZ ORDER - SECOND TT0815
VERT ORDER - FIRST CLASS I TT0815 ELLP
ORDER - FOURTH CLASS II TT0815 TT0815.The
horizontal coordinates were established by GPS
observations TT0815.and adjusted by the National
Geodetic Survey in September 1992. TT0815.This
is a SPECIAL STATUS position. See SPECIAL STATUS
under the TT0815.DATUM ITEM on the data sheet
items page. TT0815 TT0815.The orthometric
height was determined by differential leveling
TT0815.and adjusted by the National Geodetic
Survey in June 1991. TT0815 TT0815.The X, Y,
and Z were computed from the position and the
ellipsoidal ht.
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TT0815.The Laplace correction was computed from
DEFLEC99 derived deflections. TT0815 TT0815.The
ellipsoidal height was determined by GPS
observations TT0815.and is referenced to NAD 83.
TT0815 TT0815.The geoid height was determined
by GEOID99. TT0815 TT0815.The dynamic height is
computed by dividing the NAVD 88
TT0815.geopotential number by the normal gravity
value computed on the TT0815.Geodetic Reference
System of 1980 (GRS 80) ellipsoid at 45
TT0815.degrees latitude (g 980.6199 gals.).
TT0815 TT0815.The modeled gravity was
interpolated from observed gravity values.
TT0815 TT0815 North
East Units Scale Factor Converg. TT0815SPC
AK 4 - 806,092.285 510,143.003 MT
0.99990126 0 09 56.1 TT0815UTM 06 -
6,792,602.797 349,133.144 MT 0.99987887 -2
27 53.1 TT0815 TT0815! - Elev
Factor x Scale Factor Combined Factor
TT0815!SPC AK 4 - 0.99999081 x
0.99990126 0.99989208 TT0815!UTM 06 -
0.99999081 x 0.99987887 0.99986969
TT0815 TT0815
SUPERSEDED SURVEY CONTROL TT0815 TT0815 NAD
83(1986)- 61 14 18.76388(N) 149 48
40.01763(W) AD( ) 2 TT0815 NAD 27 -
61 14 20.74538(N) 149 48 32.08505(W) AD(
) 2 TT0815 NGVD 29 (??/??/92) 49.918 (m)
163.77 (f) ADJ UNCH 1 1 TT0815
TT0815.Superseded values are not recommended for
survey control. TT0815.NGS no longer adjusts
projects to the NAD 27 or NGVD 29 datums.
TT0815.See file dsdata.txt to determine how the
superseded data were derived. TT0815
TT0815_U.S. NATIONAL GRID SPATIAL ADDRESS
6VUN4913392603(NAD 83) TT0815_MARKER DD
SURVEY DISK TT0815_SETTING 7 SET IN TOP OF
CONCRETE MONUMENT TT0815_STAMPING TT AN 7 1941
TT0815_MARK LOGO USE
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NAD 83 NETWORK PROBLEMS

• NOT GPSABLE

POOR STATION ACCESSIBILITY
IRREGULARLY SPACED
POSITIONAL ACCURACY
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HIGH PRECISION GPS NETWORKSHIGH ACCURACY
REFERENCE NETWORKS(HPGN HARN)

• 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)

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HPGN - HARN1987 - 2003
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ALASKA HARN
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CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)

• Installed and Operated by various
  Federal-State-local Agencies
• More than 640 Stations
• NOAA/National Geodetic Survey
• NOAA/OAR Forecast Systems Lab
• U.S. Coast Guard - DGPS/NDGPS
• Corps of Engineers - DGPS
• FAA - WAAS/LAAS
• State DOTs
• County and City
• Academia
• Private Companies

CHL1 - CAPE HENLOPEN, DE
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CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)

• Variety of Geodetic Quality Dual-Frequency
• Antennas and Receivers
• Allen-Osborne
• Ashtech/Thales
• Leica
• Topcon
• Trimble

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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, ITRF00
  Coordinates
• Network Data Collection - Hourly Daily
• Daily 3-D Network Integrity Adjustment
• Public Data Distribution - Internet
• 10 Year On-Line Data Holding

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PLATE BOUNDARY OBSERVATORY - PBO
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NAD 83 READJUSTMENTLOWER 48

• HARN COMPLETION - SEPTEMBER 1997
• (Indiana)
• GPS HEIGHT MODERNIZATION OBSERVATIONS
• (1997 - 2003)
• (http//
• COMPLETE GPS NAD 83 3-D ADJUSTMENT
• REMOVAL OF SMALL REGIONAL DISTORTIONS
• (3 - 6 CM)
• UNIFORM COORDINATE TAG
• NAD 83 (NSRS)

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NAD 83 READJUSTMENTALASKA
Observation of Federal/Cooperative Base
Networks (e.g. Reobservation of
HPGN/HARN) Or Wait for Plate Boundary
Observatory??
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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?

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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

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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). A
  three dimensional solution to a two dimensional
  problem.

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Z
Earth-Centered Earth-Fixed (ECEF)
Coordinate System
(X,Y,Z,)
A
Latitude Longitude Ellipsoid Height
Greenwich Meridian
ZA
Earth Mass Center
- Y
- X
YA
Y
X
XA
Equator
- Z
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Z
Earth-Centered Earth-Fixed (ECEF)
Coordinate System
Y
X
Z
X
Y
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3 Parameter Molodensky Transformation
In The Real World
dZ
dY
dX
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I NEED TO TRANSFORMBETWEEN NAD 27 AND WGS 84
-4 133 174
Approx 145 in Anchorage Borough
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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

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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

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NADCON
Lat 0.12344 Lon -1.87842
N 0.12249 8 -1.88963
Lat 0.12423 Lon -1.81246
Lat 0.12568 Lon -1.83364
Lat 0.12449 Lon -1.88905
Lat 0.12640 Lon -1.85407
Lat 0.12499 Lon -1.86543
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COORDINATE TRANSFORMATION COMPARISONNAD 27 to
NAD 83(1992)

• MOLODENSKY
• ADJUSTED vs. TRANSFORMED
• Station TT AN 7
• LATITUDE
  LONGITUDE
• 61-14-18.74224
  149-48-39.96942 - PUBLISHED
• 61-14-18.72350
  149-48-40.07603 - MOLODENSKY
• 
  .01874 .10661
• 0.580 m
  1.590 m
• THIS CORRESPONDS TO A POSITIONAL
• DIFFERENCE OF 1.692 m (5.55 ft)

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COORDINATE TRANSFORMATION COMPARISON NAD
27 to NAD 83(1992)

• NADCON
• ADJUSTED vs. TRANSFORMED
• Station TT AN 7
• 
  LATITUDE LONGITUDE
• 61-14-18.74224 149-48-39.96942
  - PUBLISHED
• 61-14-18.76441
  149-48-40.01730 - NADCON
• .02217
  .04788
• 0.686
  m 0.714 m
• THIS CORRESPONDS TO A POSITIONAL
• DIFFERENCE OF 0.990 m (3.24 ft)

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