# Presentation: 816370

## National Readjustment of NAD 83

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

**Notes:**
My introduction
NGS – TSRC – NHMP 

## NATIONAL SPATIAL REFERENCE SYSTEM(NSRS)

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

## ACRONYMS         US

- NAD 83

- WGS 84

- Clark 1866

- NAVD 88

- NGVD 29

- NAD 27

- ACRONYMS         US

- ITRF

- NAD83(1986)

- NAD83(1997)

- HARN

- NSRS2007

- GRS 80

## 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 

**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**

## 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
- 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

**Horizontal Datums**

_**Cartesian system**_
**X = -2691542.5437 m**
**Y = -4301026.4260 m**
**Z = 3851926.3688 m**

_**Lat Lon**_
******** ****= 37****o**** 23’ 26.38035” N**
********  ****= 122****o**** 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)

##       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 STATESELLIPSOID DEFINITIONS

**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**

**BESSEL 1841**
**      ****a = 6,377,397.155 m  1/f = 299.1528128**

**Notes:**
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 1879.  Clarke 1866, developed by the English Geodesist A. R. Clarke was adopted in 1879 following the completion of the great Transcontinental 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!!

## 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

**International Laser Ranging Service (**_[ILRS](http://ilrs.gsfc.nasa.gov/)__)_

**International Very Long Baseline Service (**_[IVS](http://ivscc.gsfc.nasa.gov/)__)_

**International DORIS Service (**_[IDS](http://ids.cls.fr/)__)_

**International Terrestrial Reference Frame**
**4 Global Independent Positioning Technologies**

**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)**

**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/IONReport8-20-02.pdf**

**HOW MANY WGS 84s **
**HAVE THERE BEEN????**

**WORLD GEODETIC SYSTEM 1984**

- _[http://earth-info.nga.mil/GandG/publications/tr8350.2/tr8350_2.html](http://earth-info.nga.mil/GandG/publications/tr8350.2/tr8350_2.html)_

## Tectonic Plates NUVEL-1A

**Tectonic Plates NUVEL-1A**

## ITRF00 vs NAD83 velocities

**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

## 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

## Earthquakes in Contiguous US

## MEADES RANCH 1891 – KANSASOrigin for USSD-NAD-NAD27

## 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**
**                               ****few hundred Base lines        30k EDMI base lines**
**	****	****	****          ****few hundred Astro Az           5k Astro Azimuths**
**	****	****	****	****	****	****                   ****Doppler and VLBI**
**                                                                            ****1.8 million observations**
**	**

**Notes:**
This slide gives you an idea of how many stations went into each adjustment and the characteristics of the datum.  

The size and shape of the ellipsoid was recommended by the IAG (International Association of Geodesy).

The new adjustment will be defined Exactly the same-ie earth centered and with the GRS80 ellipsoid.
We will continue to use NAD83 as the datum because of legal issues in the US.
To jump ahead slightly, we will also publish ITRF coordinates as part of the transition for the future

## NAD 27 to NAD 83 (86)

**NAD 27 to NAD 83 (86)**

## 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)**

**Notes:**
Through the effort of many people, We achieved a Very consistent and accurate network based on classical (ie terrestrial) observations-and putting it into today’s terms-
After 12 years of hard labor, we were done. 
We celebrated, I took a month long vacation and lounged in our success. I was going to have it easy for the next 20 years!
But No sooner had I returned than projects with these strange new 3 dimensional observations began to arrive and the phone started to ring-why weren’t this surveys checking the control-both were first order!...

## NAD 83(86) NETWORK PROBLEMS

**NOT “GPSABLE”**
**POOR STATION ACCESSIBILITY**
**IRREGULARLY SPACED**
**POSITIONAL ACCURACY**

**Notes:**
COMPLAINTS from this new technology called ‘GPS’ were pointing out problems in our brand new datum already.
Existing marks were hard to reach, especially with a few hundred pound GPS receiver.
Questionable satellite visibility at existing stations.
GPS was already pointing out inadequacies in the network. Not just logistical but technical also-why were there decimeter differences in the coordinates using GPS and what was published as first order?
We had always prided ourselves that our network was a degree of accuracy better than the technology that surveyors were using so that it would serve as control. And it was for those that were using ‘old’ technology. But not for a very vocal group who were investing in the ‘new’ technology and for those in the research end of preparing us for the new generation of technology.

## 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)**

**Notes:**
CA HPGN 1991 only held ONE CORS (MOJAVE) along with existing VLBI 
This slide basically shows the adjustment process.
The A-Order was determined by very long GPS vectors to ‘CORS’ in Florida, Mass., and California. 
 The original eastern strain network-  also was used to define the A-order.  Unfortunately, the original eastern stain network turned out to have many problems. It was simply done too early and not enough was known (and not enough satellites were available) to produce high quality results.
LAYERED APPROACH, ending in a complete readjustment of ALL data within each state. Including classical
DATE TAG was born.  Each state with a different tag for the year it was observed.  And while we were struggling to maintain consistency, even when we did it didn’t look like we had it because adjacent stations across borders appeared to be different.
FEATHERED SHIFTS- To further complicate the issue, because not all states were done at the same time or even sequentially with their neighbors, we feathered the residual shifts into the neighboring states creating further inconsistencies in the network (although we were trying to maintain consistency without a general readjustment).

INCONSISTENCY BETWEEN STATES BEGAN!!!

## REGIONAL CORS NETWORK

**REGIONAL CORS NETWORK**

## ITRF00 – NAD 83(CORS96)

** ****_____________________________________________________________________________ **
**|                                                                             |**
**|         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                       |**
**|_____________________________________________________________________________|**

- Horiz = 0.973m
- EHt   = 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**

**Notes:**
ACURRACY BUT NOT CONSISTENCY!!

To summarize:  This slide shows how far we’ve come since 1986, really since 1927.
Unfortunately, ---  Next slide  ----

##         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.**
** **

## Slide 28

## 			                    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)

**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)**
**	****	****	****	****	**

**POSITIONAL CHANGES****Station: ASSUMPTION (KB0684)**

**Notes:**
ACURRACY BUT NOT CONSISTENCY!!

To summarize:  This slide shows how far we’ve come since 1986, really since 1927.
Unfortunately, ---  Next slide  ----

## 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**

**Notes:**
Our multiple adjustments over time have produced Inconsistencies between the states
Mass confusion with multiple epoch dates,
Consistency with the CORS, very important when we begin to utilize OPUS solutions and as people generally begin to use CORS more in their lower order surveys.
But most of all, we will now be able to remove the Order/class codes which were somewhat misleading or in error with a new way of representing the accuracy of the coordinates.
We Will readjust ALL horizontal positions and ellipsoid heights for only GPS stations.

## 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)**

**Notes:**
Basically ALL GPS data loaded through the following networks and projects
I’ve already mentioned the FBN.  Critical network tying system to CORS
– next slide --

## www.ngs.noaa.gov/NationalReadjustment

## 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

## 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

## Observation equations

- 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

- 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

- 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

- 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

- 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?**

## 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

****

**1**

**2**

**3**

**4**

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## 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

## Helmert Blocks

- Each state will comprise a separate block of data.

## 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.**

**Notes:**
Statistics from Helmert blocking will be the exact same as if we were able to adjust all data simultaneously.

Projects were placed entirely within a single block to maintain corelations between stations.

A method of network adjustment in which the network is broken up into a hierarchy of smaller networks. Adjustment is carried out first in the smallest members of the hierarchy, which are then combined by means of common points into next-larger members which also are adjusted. The process continues until the entire network has been adjusted. The final result is the same as that of a simultaneous least squares adjustment of the entire network. Helmert blocking is a special form of solving by partitioning of the normal matrix, where the observations and unknowns are partitioned geographically. The method is especially applicable to the large, sparse systems of equations typical of large geodetic networks. 

## HELMERT BLOCKING STRATEGY

**HELMERT BLOCKING STRATEGY**

**This is how each state fits into the National Readjustment**

## 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.**

**Notes:**
We will make every effort to RIGIDLY constrain the CORS coordinates which are based on a MULTIYEAR solution.

MULTIYEAR SOLUTION  This will be done in the ITRF reference frame and transformed into NAD83 (NSRS).  More on that later.  The multiyear solution is comprised of “rotating” 3-day (72hour) data sets reduced with the PAGES processing software on a computer running under the UNIX operating system, using the Precise Ephemeris over a period Of at least 2 1⁄2 years.  From analysis of these sequential data sets not only does NGS derive a very good set of coordinates, but also change over time.  You might consider this a 4-dimensional adjustment.

Stress the fact -  only GPS projects will be included!

A retrieval of every project from NGSIDB has been completed  -- next slide ---

## NEW STANDARDS FOR GEODETIC CONTROL

-                          **   ****(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**

**Notes:**
The new standards can be found in the following web site.

ERROR ELLIPSES

## SHIFTS (National results)

**  ****< 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.**

**Notes:**
I was hoping to have a plot in time for ACSM.  Unfortunately, I didn’t have time to create it.  

I can tell you, we did do a preliminary adjustment of just the FBN.

Results were less than 5 cm. in horizontal with an average of 2 cm.
         less than 10 cm. in the up component with an average shift of 4.6 cm.

## 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)**

## Slide 48

## NAD 83 Adjustment 2007 -  Ellipsoid Height

**NAD 83 Adjustment 2007 -  Ellipsoid Height**

## 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)**

**Notes:**
February 10, 2007 will be the 200th anniversary of the Coast and Geodetic Survey established by Thomas Jefferson.

## 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.**

**Notes:**
Projects submitted during the next two years will be accepted and constrained to existing network.  Readjusted after the national readjustment is complete.

Best alternative

Transforming old triangulation and traverse stations into the NAD83 (NSRS) with some sort of “national” set of seven parameters will be studied.  A lot will depend on whether or not random tests can determine valid transformation parameters

## NAD 83 (2007) and NAD 83 (CORS)

** ****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)**

**NAD 83 (2007) and NAD 83 (CORS)**

## NAD83  coordinates 1997 adjustment
Order of station 
	in the old system

Superseded coordinates do not include NAD83(97)

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

**Datasheets for excluded station**

## NAD83 (NSRS2007) datasheet

**NAD83 (NSRS2007)**** datasheet**

## ITRF00 to NAD 83 (CORS96)

## 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

## Geoid 06

**Earth’s Surface**

**Ellipsoid**

- 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

## IGA Crustal deformation for the midwest