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National Readjustment of NAD 83

Indiana Society of Professional Land Surveyors

Indianapolis, IN

January 18, 2008

NATIONAL SPATIAL REFERENCE SYSTEM(NSRS)

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

ACRONYMSUS

R

NSRS2007

NAD 27

NAVD 88

WGS 84

ITRF

NGVD 29

NAD83(1986)

NAD 83

Clark 1866

GRS 80

HARN

NAD83(1997)

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

H

b

Z

f

Y

X

l

a

-Y

+X

Cartesian system

X = -2691542.5437 m

Y = -4301026.4260 m

Z = 3851926.3688 m

Horizontal Datums- 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 earth’s 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

- Involves the origin and orientation of coordinate axes

Lat Lon

f = 37o 23’ 26.38035” N

l = 122o 02’ 16.62574” W

H = -5.4083 m

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)

b

a

S

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

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

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

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)

http://earth-info.nga.mil/GandG/publications/tr8350.2/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(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/IONReport8-20-02.pdf

HOW MANY WGS 84s

HAVE THERE BEEN????

DATUM = WGS 84

RELEASED - SEPTEMBER 1987

BASED ON OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS

ITRF00 vs NAD83 velocities

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

- Inter-seismic phase when elastic strain accumulates in the crest around the fault

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

MEADES RANCH 1891 – KANSASOrigin for USSD-NAD-NAD27

COMPARISON OF DATUM ELEMENTS

NAD 27NAD 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

few hundred Base lines 30k EDMI base lines

few hundred Astro Az 5k Astro Azimuths

Doppler and VLBI

1.8 million observations

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)

NAD 83(86) NETWORK PROBLEMS

NOT “GPSABLE”

POOR STATION ACCESSIBILITY

IRREGULARLY SPACED

POSITIONAL ACCURACY

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)

_____________________________________________________________________________

| |

| 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

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

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.

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.

KB0684;SPC IL W - 317,315.488 796,100.180 MT 1.00005484 +0 42 40.6

KB0684;SPC IL W - 1,041,059.23 2,611,872.01 sFT 1.00005484 +0 42 40.6

KB0684;SPC IL E - 316,974.300 238,460.283 MT 1.00002161 -0 27 19.6

KB0684;SPC IL E - 1,039,939.85 782,348.45 sFT 1.00002161 -0 27 19.6

KB0684;UTM 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

KB0684:SPC IL W - ASSUMPTION 1920 TP 1976 010 03 10.2

KB0684:SPC IL E - ASSUMPTION 1920 TP 1976 011 13 10.4

KB0684:UTM 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.

POSITIONAL CHANGES the ellipsoidal ht.Station: 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)

164.133 0.008 m (0.03 ft)

Reasons for Readjustment the ellipsoidal ht.

- 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

NSRS(2007) READJUSTMENT of NAD 83 the ellipsoidal ht.

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)

www.ngs.noaa.gov/NationalReadjustment the ellipsoidal ht.

Errors the ellipsoidal ht.

- All real observations contain errors
- Two types of errors
- Random errors which mean to zero
- systematic errors which do not

- Two types of errors
- Least square will only give improved results if your errors are predominantly random

Random error

Systematic error

A the ellipsoidal ht.

B

1

2

3

7

11

4

5

6

8

9

10

12

Example of redundancySuppose 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

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

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.

Least Square condition unknown residual to solve for plus the distance

- 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

Weighting unknown residual to solve for plus the distance

- 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

Minimally Constrained Adjustment unknown residual to solve for plus the distance

- 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?

Critical unknown residual to solve for plus the distancet

Critical t

Outliers

Outliers

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

4

3

2

1

1

2

3

4

Fully Constrained Adjustment unknown residual to solve for plus the distance

- 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

Helmert Blocks unknown residual to solve for plus the distance

- Each state will comprise a separate block of data.

Helmert Blocks unknown residual to solve for plus the distance

- 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.

You are here unknown residual to solve for plus the distance

HELMERT BLOCKING STRATEGY

This is how each state fits into the National Readjustment

The National Readjustment General Comments unknown residual to solve for plus the distance

- 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.

NEW STANDARDS FOR GEODETIC CONTROL unknown residual to solve for plus the distance

(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
- Will not use distance dependent expression
- Order/Class codes will no longer be used

SHIFTS (National results) unknown residual to solve for plus the distance

< 5 cm. in the horizontal component with an average shift of 2.2 cm.

< 10 cm. in the vertical component with

an average shift of 4.6 cm.

ILLINOIS STATISTICS unknown residual to solve for plus the distance

- 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)

NAD 83 Adjustment 2007 - Ellipsoid Height unknown residual to solve for plus the distance

Time-line for National Readjustment unknown residual to solve for plus the distancePositions 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)

For Stations not Included unknown residual to solve for plus the distance

- 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.

NAD 83 (2007) and NAD 83 (CORS) unknown residual to solve for plus the distance

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)

Datasheets for excluded station unknown residual to solve for plus the distance

NAD83 coordinates 1997 adjustment

Order of station

in the old system

Superseded coordinates do not include NAD83(97)

Ortho height unknown residual to solve for plus the distance

Ellip Ht GPS

Epoch date

accuracy

Datum tag

NAD83 (NSRS2007) datasheetITRF00 to NAD 83 (CORS96) unknown residual to solve for plus the distance

New procedures for data submission for horizontal projects unknown residual to solve for plus the distance

- 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

h unknown residual to solve for plus the distance

h

h

h

H

h

H

H

H

N

N

N

H

N

Composite Geoid

N

0.27m in

Joilet IL

Gravity Geoid

Geoid 06Earth’s Surface

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

Ellipsoid

IGA Crustal deformation for the midwest unknown residual to solve for plus the distance

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