National Readjustment of NAD 83

1
National Readjustment of NAD 83

• Indiana Society of Professional Land Surveyors
• Indianapolis, IN
• January 18, 2008

2
NATIONAL SPATIAL REFERENCE SYSTEM(NSRS)

• Consistent National Coordinate System
• Latitude
• Longitude
• Height
• Scale
• Gravity
• Orientation
• and how these values change with time

3
ACRONYMS US
R
NSRS2007
NAD 27
NAVD 88
WGS 84
ITRF
NGVD 29
NAD83(1986)
NAD 83
Clark 1866
GRS 80
HARN
NAD83(1997)
4
NATIONAL SPATIAL REFERENCE SYSTEM

• North American Datum of 1983 (NAD 83)
• North American Vertical Datum of 1988 (NAVD 88)
• First civilian datums designed to be consistent
  with space-based observations (GPS)
• First civilian datums to be best-fitting globally
  not locally
• First geodetic reference systems to be Accessible
  through Continuously Operating Reference Stations
  (CORS) and derived products
• First geodetic reference systems to be available
  free from WWW
• Only reference system to freely integrate data
  from
• outside sources
• MULTIPURPOSE Supports Geodesy, Geophysics, Land
  Surveying, Navigation, Mapping, Charting and GIS
• ACTIVE Accessible through Continuously
  Operating Reference Stations (CORS) and derived
  products

5
Horizontal Datums
Cartesian system X -2691542.5437 m Y
-4301026.4260 m Z 3851926.3688 m

• A horizontal datum is the coordinate system that
  we use to locate ourselves on the earth
• Involves the origin and orientation of coordinate
  axes
• geocentric cartesian (X,Y,Z)
• Usually the origin is near the center of mass of
  the earth
• one axis intersects the earths surface at the
  intersection of the prime meridian and the
  equator
• and a reference ellipsoid
• Latitude Longitude and height
• Specific geodetic datums are usually given
  distinctive names.
• North American Datum of 1983,
• International Terrestrial Reference Frame (YYYY)
• WGS84

Lat Lon f 37o 23 26.38035 N l 122o 02
16.62574 W H -5.4083 m
6
GEODETIC DATUMS

• Classical
• Horizontal 2 D (Latitude and Longitude) (e.g.
  NAD 27, NAD 83 (1986))
• Vertical 1 D (Orthometric Height) (e.g. NGVD
  29, NAVD 88)
• Contemporary
• PRACTICAL 3 D (Latitude, Longitude and
  Ellipsoid Height) Fixed and Stable Coordinates
  seldom change (e.g. NAD 83 (1996) or NAD 83 (NSRS
  2007))
• SCIENTIFIC 4 D (Latitude, Longitude,
  Ellipsoid Height, Velocity) Coordinates change
  with time (e.g. ITRF00, ITRF05)

7
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

8
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
9
International Earth Rotation and Reference
System Service(IERS)(http//www.iers.org)
The International Terrestrial Reference System
(ITRS) constitutes a set of prescriptions and
conventions together with the modeling required
to define origin, scale, orientation and time
evolution ITRS is realized by the International
Terrestrial Reference Frame (ITRF) based upon
estimated coordinates and velocities of a set of
stations observed by Very Long Baseline
Interferometry (VLBI), Satellite Laser Ranging (
SLR), Global Positioning System and GLONASS
(GNSS), and Doppler Orbitography and Radio-
positioning Integrated by Satellite ( DORIS).
Plate tectonics is accommodated giving each
coordinate a velocity ITRF89, ITRF90, ITRF91,
ITRF92, ITRF93, ITRF94, ITRF95, ITRF96, ITRF97,
ITRF2000, ITRF2005
10
International Terrestrial Reference Frame 4
Global Independent Positioning Technologies
International Global Navigation Satellite Systems
Service (IGS)
International Laser Ranging Service (ILRS)
International Very Long Baseline Service (IVS)
International DORIS Service (IDS)
11
WORLD GEODETIC SYSTEM 1984
http//earth-info.nga.mil/GandG/publications/tr835
0.2/tr8350_2.html
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)
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 RELEASED - SEPTEMBER 1987 BASED ON
OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS
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//earth-info.nima.mil/GandG/sathtml/IONRepor
t8-20-02.pdf
HOW MANY WGS 84s HAVE THERE BEEN????
12
Tectonic Plates NUVEL-1A
13
ITRF00 vs NAD83 velocities
14
Seismic cycle

• Seismic cycle consists of 2 main phases
• Inter-seismic phase when elastic strain
  accumulates in the crest around the fault
• Strain is widely distributed
• co-seismic phase when elastic strain is converted
  to slip on the fault

15
model of the secular field

• An analytical model representing horizontal
  crustal motion
• Incorporates all major active faults in a single
  model.
• Provides a more accurate model of crustal
  deformation in western US
• data comprise
• 4890 GPS velocities
• 170 fault slip rates from paleoseismic paleomag
  studies
• 258 fault slip vectors taken from earthquakes and
  geologic studies

16
Earthquakes in Contiguous US
17
MEADES RANCH 1891 KANSASOrigin for
USSD-NAD-NAD27
18
COMPARISON OF DATUM ELEMENTS

• NAD 27
  NAD 83
• ELLIPSOID CLARKE 1866
  GRS80
• 
  a6,378,206.4 m a6,378,137 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
• few hundred Base
  lines 30k EDMI base lines
• few hundred Astro Az 5k
  Astro Azimuths
• Doppler and VLBI
• 
  1.8 million
  observations

19
NAD 27 to NAD 83 (86)
20
Results of NAD83(86)

• Network Accuracy - 1 Meter
• Local Accuracy First-Order
• (1 part in 100,000)
• Second-Order
• (1 part in 50,000)
• Third-Order
• (1 part in 10,000)

21
NAD 83(86) NETWORK PROBLEMS

• NOT GPSABLE
• POOR STATION ACCESSIBILITY
• IRREGULARLY SPACED
• POSITIONAL ACCURACY

22
HARN/HPGN ADJUSTMENT

• A-Order Adjusted to VLBI-Existing FBN-CORS
• B-Order Adjusted to A-Order
• Existing Horizontal (Conventional GPS)
  Readjusted to A/B-Order
• New Adjustment Date Tag e.g. NAD83(1997)

23
REGIONAL CORS NETWORK
24
SPRINGFIELD (ILSA), ILLINOIS
__________________________________________________
___________________________

Antenna Reference Point(ARP)
SPRINGFIELD CORS ARP
--------------------------------------------------

PID DH3759



ITRF00 POSITION (EPOCH 1997.0)

Computed in June 2005 using 14 days of data.
X
33385.872 m latitude 39 46 43.08683 N
Y -4908474.031 m
longitude 089 36 37.07435 W
Z 4059224.563 m ellipsoid height
152.900 m

ITRF00 VELOCITY

Predicted with HTDP_2.7 June 2005.
VX -0.0168
m/yr northward -0.0018 m/yr
VY -0.0015 m/yr eastward
-0.0168 m/yr VZ
-0.0012 m/yr upward 0.0003 m/yr



NAD_83 (CORS96)
POSITION (EPOCH 2002.0)
Transformed from ITRF00 (epoch
1997.0) position in Jun. 2005.
X 33386.406 m latitude 39 46
43.06026 N Y
-4908475.428 m longitude 089 36 37.05230
W Z 4059224.662 m
ellipsoid height 154.039 m

NAD_83 (CORS96)
VELOCITY
Transformed from ITRF00 velocity in
Jun. 2005.
VX 0.0000 m/yr northward 0.0000 m/yr
VY 0.0000 m/yr
eastward 0.0000 m/yr
VZ -0.0000 m/yr upward
0.0000 m/yr
_______________________________________________
______________________________
ITRF00 NAD 83(CORS96) DHoriz 0.973m DEHt
1.139m
25
IMPROVING POSITIONAL ACCURACY

• TIME NETWORK LOCAL
• NETWORK SPAN ACCURACY ACCURACY
• NAD 27 1927-1986 10 METERS (1 part in
  100,000)
• NAD83(86) 1986-1990 1 METER (1 part in
  100,000)
• HARN 1990-1997 0.1 METER B-order (1.0
  ppm)
• A-order (0.1
  ppm)
• CORS 1996 - 0.01 meter 0.01 meter

26
National Geodetic Survey, Retrieval
Date DECEMBER 6, 2007 KB0684

KB0684 DESIGNATION -
ASSUMPTION KB0684 PID - KB0684 KB0684
STATE/COUNTY- IL/CHRISTIAN KB0684 USGS QUAD
- ASSUMPTION (1982) KB0684 KB0684
CURRENT SURVEY CONTROL KB0684
__________________________________________________
_________________ KB0684 NAD 83(2007)- 39 31
12.72891(N) 089 02 56.47681(W) ADJUSTED
KB0684 NAVD 88 - 196.394 (meters)
644.34 (feet) ADJUSTED KB0684
__________________________________________________
_________________ KB0684 EPOCH DATE -
2002.00 KB0684 X - 81,771.588
(meters) COMP KB0684 Y
- -4,926,226.861 (meters)
COMP KB0684 Z - 4,037,138.456
(meters) COMP KB0684
LAPLACE CORR- -0.20 (seconds)
DEFLEC99 KB0684 ELLIP HEIGHT-
164.133 (meters) (02/10/07) ADJUSTED
KB0684 GEOID HEIGHT- -32.27 (meters)
GEOID03 KB0684 DYNAMIC HT -
196.282 (meters) 643.97 (feet) COMP
KB0684 KB0684 ------- Accuracy Estimates (at
95 Confidence Level in cm) -------- KB0684
Type PID Designation
North East Ellip KB0684 ---------------------
----------------------------------------------
KB0684 NETWORK KB0684 ASSUMPTION
0.57 0.41 1.76 KB0684
--------------------------------------------------
----------------- KB0684 MODELED GRAV-
980,049.7 (mgal) NAVD 88
KB0684 KB0684 VERT ORDER - FIRST CLASS I
KB0684 KB0684.The horizontal coordinates were
established by GPS observations KB0684.and
adjusted by the National Geodetic Survey in
February 2007. KB0684 KB0684.The datum tag of
NAD 83(2007) is equivalent to NAD 83(NSRS2007).
KB0684.The horizontal coordinates are valid at
the epoch date displayed above. KB0684.The epoch
date for horizontal control is a decimal
equivalence KB0684.of Year/Month/Day. KB0684
KB0684.The orthometric height was determined by
differential leveling KB0684.and adjusted in
June 1991. KB0684 KB0684.Photographs are
available for this station.
27
KB0684.The X, Y, and Z were computed from the
position and the ellipsoidal ht. KB0684.The
ellipsoidal height was determined by GPS
observations KB0684.and is referenced to NAD
83. KB0684 KB0684.The geoid height was
determined by GEOID03. KB0684 KB0684 KB0684
North East Units
Scale Factor Converg. KB0684SPC IL W -
317,315.488 796,100.180 MT 1.00005484 0
42 40.6 KB0684SPC IL W - 1,041,059.23
2,611,872.01 sFT 1.00005484 0 42 40.6
KB0684SPC IL E - 316,974.300 238,460.283
MT 1.00002161 -0 27 19.6 KB0684SPC IL E
- 1,039,939.85 782,348.45 sFT 1.00002161
-0 27 19.6 KB0684UTM 16 - 4,376,511.174
323,870.958 MT 0.99998195 -1 18 15.2
KB0684 KB0684! - Elev Factor x
Scale Factor Combined Factor KB0684!SPC IL W
- 0.99997425 x 1.00005484
1.00002909 KB0684!SPC IL E - 0.99997425 x
1.00002161 0.99999586 KB0684!UTM 16
- 0.99997425 x 0.99998195 0.99995620
KB0684 KB0684 Primary Azimuth
Mark Grid Az KB0684SPC IL W
- ASSUMPTION 1920 TP 1976
010 03 10.2 KB0684SPC IL E - ASSUMPTION
1920 TP 1976 011 13 10.4
KB0684UTM 16 - ASSUMPTION 1920 TP 1976
012 04 06.0 KB0684
KB0684-------------------------------------------
-------------------------- KB0684 PID
Reference Object Distance
Geod. Az KB0684
dddmmss.s
KB0684 KB1363 ASSUMPTION 1920 TP 1976
APPROX. 0.5 KM 0104550.8 KB0684 KB0685
ASSUMPTION RM 2 7.062
METERS 01146 KB0684 KB1368 ASSUMPTION AZ
A PT 1976 489.179 METERS 0994730.6
KB0684 KB1367 ASSUMPTION AZ MK
483.552 METERS 1001424.8 KB0684 KB1362
ASSUMPTION A PT 1976 9.725
METERS 24325 KB0684 KB1361 ASSUMPTION MUN
TANK 145.607 METERS 24654
KB0684 CI6654 ASSUMPTION RM
21.330 METERS 26717 KB0684 KB0686
ASSUMPTION RM 3 26.388
METERS 27304 KB0684-----------------------
----------------------------------------------
KB0684 KB0684
SUPERSEDED SURVEY CONTROL KB0684 KB0684 ELLIP
H (10/15/04) 164.141 (m)
GP( ) 4 2 KB0684 NAD 83(1997)- 39 31
12.72890(N) 089 02 56.47672(W) AD( ) B
KB0684 ELLIP H (07/17/98) 164.137 (m)
GP( ) 4 1 KB0684 NAD
83(1986)- 39 31 12.73871(N) 089 02
56.46320(W) AD( ) 2 KB0684 NAD 27 -
39 31 12.59480(N) 089 02 56.15910(W) AD(
) 2 KB0684 NAVD 88 (07/17/98) 196.39 (m)
644.3 (f) LEVELING 3 KB0684 NGVD
29 (??/??/92) 196.484 (m) 644.63 (f)
ADJ UNCH 1 1 KB0684 KB0684.Superseded values
are not recommended for survey control.
KB0684.NGS no longer adjusts projects to the NAD
27 or NGVD 29 datums. KB0684.See file dsdata.txt
to determine how the superseded data were
derived.
28
(No Transcript)
29
POSITIONAL CHANGESStation ASSUMPTION (KB0684)

• TIME
  POSITION
• DATUM SPAN Lat/Long/E Hgt
  POSITION SHIFT
• USSD/NAD
  1901 1927 39-31-12.70400
• 89-02-56.05500
  
  Undetermined
• NAD 27
  1927 1986 39-31-12.59480
• 89-02-56.15910
  4.186 m (13.73 ft)
• Undetermined
• NAD 83 (86) 1986 1997
  39-31-12.73871
• 89-02-56.46320 8.512 m (27.93 ft)
• 
  
  Undetermined
• NAD 83 (97) 1997 2007
  39-31-12.72890
• 89-02-56.47672 0.442 m (1.45 ft)
• 
  164.141
• NAD 83 (07) 2007 (?)
  39-31-12.72891 89-02-56.47681 0.002 m
  (0.06 ft)

30
Reasons for Readjustment

• Multiple epoch dates
• Inconsistencies between states
• Need to be Consistent with CORS
• Compute Network and Local accuracies
• Some HARNs exhibit 4 7 cm difference with CORS
• September 24, 2003 NGS Executive Steering
  Committee approved a plan for the readjustment of
  the horizontal positions and ellipsoid heights
  for GPS stations in the contiguous United States.
• Orthometric Height adjustment will not be
  attempted

31
NSRS(2007) READJUSTMENT of NAD 83

• ONLY GPS DATA WAS USED
• CONTINUOUSLY OPERATING REFERENCE STATIONS
• FEDERAL BASE NETWORK (A B)
• COOPERATIVE BASE NETWORK (B)
• USER DENSIFICATION NETWORK (First)
• AIRPORT SURVEYS (B First)

32
www.ngs.noaa.gov/NationalReadjustment
33
Errors

• All real observations contain errors
• Two types of errors
• Random errors which mean to zero
• systematic errors which do not
• Least square will only give improved results if
  your errors are predominantly random

Random error
Systematic error
34
Example of redundancy
Suppose we are trying to determine the distance
between two points We have 5
measurements all have equal precision Any one
measurement is enough to determine the distance
but because every measurement contains
measurement errors so each measurement gives a
slightly different result
35
Observation equations

• For each observation we can write an equation
  relating the parameter we are trying to determine
  (the distance) to the observation and the
  residual.

• This means that each time we add an equation, we
  have one unknown residual to solve for plus the
  distance
• So we will never have enough equations to solve
  for the unknowns

36
Least Square condition

• Since we do not have 1 equation per unknown
• We have to add at least one more so we have
  enough information to determine all of the
  unknowns
• We add a condition that the sum of the squares of
  all of the residuals is a minimum
• This just means that the data is as close to the
  parameters (in this case the mean value) as
  possible

37
Weighting

• All least square adjustments include some sort of
  estimate of the accuracy of the measurements
• This allows measurements that are precise to have
  more importance (or weight) than approximate
  measurements
• The weighting for each observation is equal to
  the inverse square of the standard deviation
• The idea is that if then error is small the
  weighting the weighting is large

38
Minimally Constrained Adjustment

• Hold the minimum number of control points fixed
  to allow the least square process to work
• One fixed point for GPS
• 2 for triangulation survey without distance
  measurements
• The purpose of this adjustment is to
• Check the internal consistency of the network
• Detect blunders or ill-fitting observations
• Obtain accurate error estimates

How big do you make the bolt holes?
39
Residuals

• Residuals are the difference between the observed
  survey measurements and values calculated form
  coordinates from the least squares adjustment
• They follow a known statistical distribution
• and we can use statistics to identify
  observations with residuals are large enough to
  represent blunders that should be investigated
  further

s
1
2
3
4
1
2
3
4
40
Fully Constrained Adjustment

• Hold all control points in the network fixed at
  values from the NGS database
• Minimum of 2 for GPS surveys
• 3 for triangulation survey without distance
  measurements
• The purpose of this adjustment is to
• Reference the network to existing control and
  develop final coordinates for the new control
  points that are being established
• Verify existing control.
• If any control points are wrong
• the standard error of unit weight and residuals
  will increase compared to the minimally
  constrained adjustment

41
Helmert Blocks

• Each state will comprise a separate block of data.

42
Helmert Blocks

• CORS/CGPS provided control at the top block
• CGPS coordinates were determined by Scripps
  Sector utility projected to the 2007.0 epoch.
• An attempt was made to create a separate block of
  data for each state to minimize the number of
  junction observations between blocks.
• California, Florida, Minnesota, North and South
  Carolina were broken into multiple blocks because
  of the number of stations located in these blocks.

43
HELMERT BLOCKING STRATEGY
This is how each state fits into the National
Readjustment
44
The National Readjustment General Comments

• The CORS/CGPS sites were the control
• Only GPS projects participated
• The FBN/CBN Surveys are a key element since these
  are high accuracy (2 cm) surveys that tie the
  HARN to the CORS throughout the contiguous United
  States and provide more accurate values for the
  ellipsoid heights of most HPGN stations.

45
NEW STANDARDS FOR GEODETIC CONTROL

• (http//fgdc.er.usgs.g
  ov/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
• Will not use distance dependent expression
• Order/Class codes will no longer be used

46
SHIFTS (National results)

• lt 5 cm. in the horizontal component with
  an average shift of 2.2 cm.
• lt 10 cm. in the vertical component with
• an average shift of 4.6 cm.

47
ILLINOIS STATISTICS

• Total of Stations 2515
• Max Horizontal Shift 0.106 (m)
• Average Hz Shift 0.011 (m)
• Max Vertical Shift 0.173 (m)
• Average Vt. Shift 0.014 (m)

48
(No Transcript)
49
NAD 83 Adjustment 2007 - Ellipsoid Height
50
Time-line for National Readjustment Positions
and Ellipsoid Heights

• All projects loaded in the NGS database prior to
  November 15, 2005 were included in the National
  Readjustment
• Projects submitted after 11/15/2005 were accepted
  and loaded into the database but were not
  included in the readjustment
• Completed adjustment by February 10, 2007
  deadline
• New Datasheets including new positions and
  network accuracies available now.
• Project Report (pending)

51
For Stations not Included

• NGS recommends that NAD 83 data that is NOT part
  of the NSRS readjustment be readjusted by
  contractor/user with the original observations.
• Because of the relatively small shifts
  anticipated, a model such as NADCON will NOT be
  developed between previously determined GPS
  coordinates.

52
NAD 83 (2007) and NAD 83 (CORS)
National Geodetic Survey, Retrieval Date
NOVEMBER 30, 2007 KG0640

KG0640 FBN - This is a Federal Base
Network Control Station. KG0640 DESIGNATION -
MEADES RANCH RESET KG0640 PID -
KG0640 KG0640 STATE/COUNTY- KS/OSBORNE KG0640
USGS QUAD - MEADES RANCH (1978) KG0640
KG0640 CURRENT SURVEY
CONTROL KG0640 _________________________________
__________________________________ KG0640 NAD
83(2007)- 39 13 26.71218(N) 098 32
31.74604(W) ADJUSTED KG0640 NAVD 88 -
600.3 (meters) 1969. (feet) GPS
OBS KG0640 __________________________________
_________________________________ KG0640 EPOCH
DATE - 2002.00 KG0640 X -
-734,972.580 (meters) COMP
KG0640 Y - -4,893,188.504 (meters)
COMP KG0640 Z -
4,011,982.822 (meters) COMP
KG0640 LAPLACE CORR- -2.96 (seconds)
DEFLEC99 KG0640 ELLIP HEIGHT-
573.979 (meters) (02/10/07)
ADJUSTED KG0640 GEOID HEIGHT- -26.35
(meters) GEOID03
National Geodetic Survey, Retrieval Date
NOVEMBER 30, 2007 DI3428

DI3428 CORS - This is a GPS Continuously
Operating Reference Station. DI3428 DESIGNATION
- KSU1_KSUN_KS2006 CORS ARP DI3428 CORS_ID
- KSU1 DI3428 PID - DI3428 DI3428
STATE/COUNTY- KS/RILEY DI3428 USGS QUAD -
SWEDE CREEK (1982) DI3428 DI3428
CURRENT SURVEY CONTROL DI3428
__________________________________________________
_________________ DI3428 NAD 83(CORS)- 39 06
02.67730(N) 096 36 34.09342(W) ADJUSTED
DI3428 NAVD 88 -
DI3428
__________________________________________________
_________________ DI3428 EPOCH DATE -
2002.00 DI3428 X - -570,503.804
(meters) COMP DI3428 Y
- -4,923,592.374 (meters)
COMP DI3428 Z - 4,001,208.587
(meters) COMP DI3428 ELLIP
HEIGHT- 326.622 (meters)
(01/??/07) ADJUSTED DI3428 GEOID HEIGHT-
-29.93 (meters) GEOID03
DI3428 HORZ ORDER - SPECIAL (CORS) DI3428
ELLP ORDER - SPECIAL (CORS)
53
Datasheets for excluded station

• NAD83 coordinates 1997 adjustment
• Order of station
• in the old system
• Superseded coordinates do not include NAD83(97)

54
NAD83 (NSRS2007) datasheet
55
ITRF00 to NAD 83 (CORS96)
56
New procedures for data submission for horizontal
projects

• All projects will have to be adjusted using only
  NSRS2007 control points
• All projects will have to have at least one CORS
  tie
• No error scaling is required now
• The program MODGEE.EXE will not be run
• Changes soon may be required in the final free
  adjustment
• This may involve weighting the control using
  accuracies form the datasheets

57
Geoid 06

• A new geoid Geoid Warped to fit NRSR2007
  ellipsoid heights will be released soon
• The next height datum will be based on the
  gravity geoid

Earths Surface
Ellipsoid
58
IGA Crustal deformation for the midwest