THE EARTHS SURFACE IS CHANGING

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2 THE EARTHS SURFACE IS CHANGING

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4 Vertical Motion Associated with Subduction Hyndman and Wang, 1994

5 NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Positioning America for the Future

6 Horizontal velocities in the western U.S. relative to the North American Datum of 1983 as derived from geodetic observations. -Times 8 years ( ) -As will be seen realized with NAD 83(2011)Epoch2010 (tent. name) Slide from R. Snay, NGS

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10 THE PROJECT

11 CONUS Conterminous United States CORS Continuously Operating Reference Stations FGDC Federal Geographic Data Committee GNSS Global Navigation Satellite System GPS Global Positioning System HTDP Horizontal Time Dependent Positioning (NGS software) IGS International GNSS Service MYCS Multi-Year CORS Solution Epoch An epoch is a moment in time used as a reference point.

12 NA2011 National Adjustment of 2011 NAD 83 North American Datum of 1983 NAVD 88 North American Vertical Datum of 1988 NADCON North American Datum Conversion (NGS software) NGS National Geodetic Survey NGSIDB National Geodetic Survey Integrated Data Base OPUS Online Positioning User Service

13 Original realization completed in 1986 Consisted (almost) entirely of classical (optical) observations High Precision Geodetic Network (HPGN) and High Accuracy Reference Network (HARN) realizations Most done in 1990s, essentially stateby-state Based on GNSS but classical stations included in adjustments National Re-Adjustment of 2007 NAD 83(CORS96) and (NSRS2007) Simultaneous nationwide adjustment (GNSS only) New realization: NAD 83(2011) epoch

14 Multi-Year CORS Solution (MYCS) Reprocessing of all CORS GPS data 1994-present 2264 CORS & global stations NAD 83 computed by transformation from IGS08 National Adjustment of 2011 (NA2011) New adjustment of GNSS passive control GNSS vectors tied (and constrained) to CORS NAD 83(2011) epoch Approximately 80,000 stations and 400,000 GNSS vectors Realization SAME for CORS and passive marks This is NOT a new datum! (still NAD 83)

15 The project is officially called the National Adjustment of 2011, abbreviated as NA2011. It is a nationwide, geometric adjustment of passive stations with positions determined using Global Navigation Satellite System (GNSS) technology and data, which includes the Global Positioning System (GPS).

16 NA2011 is called geometric because it will yield new values for latitude, longitude, and ellipsoid height; it will NOT affect the orthometric heights of stations. However, a future nationwide vertical adjustment is being considered to determine GNSSderived orthometric heights based on the results of NA2011

17 NAD 83(2011) epoch is datum tag year adjustment complete is epoch date (January 1, 2010) Date associated with coordinates of control station Frame fixed to North American tectonic plate Includes California, Puerto Rico, and US Virgin Islands NAD 83(PA11) epoch Frame fixed to Pacific tectonic plate NAD 83(MA11) epoch Frame fixed to Mariana tectonic plate

18 There has been no datum change, that is, the origin, scale and orientation of NAD 83(2011) are identical to those of NAD 83(CORS96). The changes in coordinates are driven by multiple factors including the switch to absolute antenna calibrations, new/revised processing algorithms, improved discontinuity identification, longer data sets, and our improved definition of the global reference frame. However for the end user the biggest change is caused by the new reference epoch, which has changed by 8 years from to

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20 CORS

21 ITRF NAD83(CORS96) Relative antenna calibration ITRF2000, defined by only 8 global stations IGS08 (2011) NAD83(2011) Absolute ITRF2008 uses ~230 stations What does this all mean? Average differences of NAD 83(2011) epoch minus NAD 83(CORS96) epoch : East cm; North cm; Vertical cm Current Upcoming < 2 mm +/- 1-2 cm (nationally)

22 The National Geodetic Survey (NGS) operates the Continuously Operating Reference Station (CORS) Network that provides Global Navigation Satellite System (GNSS) data in RINEX format, and associated positions. Currently NGS provides these coordinates in ITRF00 epoch , and in NAD 83(CORS96) epoch NGS has completed a full reanalysis of all data from CORS and a set of global sites with the goal to compute a fully consistent set of coordinates, GPS satellite orbits and Earth Orientation Parameters (EOP). This initial Multi-Year CORS (MYCS1) effort is the first of a series reprocessing projects that will occur periodically in the coming years.

23 Slide by J. Griffiths and the MYCS Team

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25 REGIONAL CORS NETWORK

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27 NAD 83 CORS 96 VS NAD WASHINGTON NORTH ZONE US FEET NAD 83/CORS 96 US FT NAD US FT DIFFERENCE US FT NAME PID# NORTHING EASTING ELLIPSE NAME PID# NORTHING EASTING ELLIPSE NORTH EAST ELLIPSE BREW DK BREW DK CHWK DE CHWK DE CPXF AJ CPXF AJ CHZZ AJ CHZZ AJ FTS1 AF FTS1 AF FTS2 AF FTS2 AF FTS5 DK FTS5 DK FTS6 DK FTS6 DK GOBS AF GOBS AF GWEN AF GWEN AF GWN2 AF GWN2 AF GWN5 DJ GWN5 DJ GWN6 DJ GWN6 DJ KELS AF KELS AF LIND AH LIND AH LINH CQ LINH CQ LNGB DG NEAH AF NEAH AF

28 ORS1 DG ORS1 DG ORS2 DG ORS2 DG P020 DG P020 DG P376 DH P376 DH P415 DH P415 DH P420 DG P420 DG P432 DG P432 DG P446 DK P446 DK P451 DH P451 DH P687 DH P687 DH P690 DH P690 DH P693 DH P693 DH P695 DH P695 DH P696 DH P696 DH P697 DH P697 DH P698 DH P698 DH P699 DH P699 DH P702 DH P702 DH PABH AF PABH AF PRDY DF RPT1 AF RPT1 AF RPT2 AF RPT2 AF RPT5 DK RPT5 DK RPT6 DK RPT6 DK SC00 AJ SC00 AJ SEAI DH SEAI DH SEAT AF SEAT AF SEAW AH SEAW AH SEDR AF SEDR AF

29 SPN1 AJ SPN1 AJ SPN2 AJ SPN2 AJ SPN5 DK SPN5 DK SPN6 DK SPN6 DK THUN DF TWHL AJ TWHL AJ WHD1 AF WHD1 AF WHD2 AF WHD2 AF WHD5 DK WHD5 DK WHD6 DK WHD6 DK YELM DF ZSE1 DF ZSE1 DF

30 Why is NGS doing a national adjustment a mere 4 years after the last adjustment

31 How will it be done? longer data spans absolute antenna calibrations satellite transmitting and ground receiving antennas new network design added redundancy Delaunay triangulation over global sites and CORS backbone tie remaining CORS to backbone as stars IERS 2003 Conventions generally implemented updated model for station displacements due to ocean tidal loading updated models for troposphere propagation delays use current frame; first attempt to obtain a full history of products in a fully consistent framework. Contribute NGS reprocessed orbits, to International GNSS Service) Slide by J. Griffiths and the MYCS Team

32 In order for the coordinates of passive stations to maintain consistency with the CORS representation of the NSRS, NGS will be doing another national adjustment this year The datum tag that will be adopted for both CORS (active) and passive is NAD83(2011) CORS (only) will be the control for the LSA

33 For NGS products and services to be mutually aligned, it is necessary to perform an adjustment (constrained to the new MYCS coordinates) of as many GNSS vectors held in the NGS Integrated Data Base (NGSIDB) as possible.

34 These vectors represent GNSS observations between passive stations, and, importantly, between passive stations and CORS (i.e., active stations). The vectors tied to CORS will make it possible to determine new coordinates on passive control that are consistent with the MYCS.

35 All CORS with GNSS data archived by NGS were included in the MYCS. The only CORS not included are those that have no archived data, which consists only of a small number of Cooperative CORS. Of these, the only ones excluded were decommissioned prior to becoming part of the NGS CORS network and did not provide their historic GNSS data to NGS. The Cooperative CORS program is no longer in effect, and so all currently operating CORS are simply CORS, and they are all included in the MYCS. A list of previously operating CORS that were not used in the MYCS will be provided in the near future.

36 NGS is in the process of readjusting most, if not all, of the passive vector control in the NGSIDB to make it consistent with MYCS1 solution. The results of this adjustment (National Readjustment of 2011) will have the same reference frame tag and epoch date as the MYCS1, namely NAD 83(2011) epoch

37 A passive station is, in NGS terminology, a conventional ground station, e.g., a brass disk set in a substantial structure, a steel rod driven vertically into the ground until refusal, or other such stable physical marks that can be occupied with survey equipment. An active station is a GNSS antenna (and associated receiver) in a fixed location providing GNSS data to the public, such as a CORS,WSRN

38 GNSS observations (vectors) for all passive control stations in the NGS Integrated Data Base (NGSIDB) connected (directly or indirectly) to CORS with MYCS coordinates as of July 31, 2011 may be included in the adjustment. However, being included in the adjustment only assures that the observations will be evaluated for their possible inclusion in the final adjustment. As with any survey control network adjustment, observations that do not fit well with other observation (i.e., outliers ) will be rejected. In some cases, this may result in passive control stations being excluded from NA2011, in which case they will retain their previous datum tag. Projects submitted after July 31, 2011 will be published with NAD 83(NSRS2007) coordinates until NA2011 is completed. At that time those projects in the queue will be adjusted to the new realization and published on NAD 83(2011) epoch

39 Any passive station that does not have acceptable GNSS data will be excluded from NA2011, as will stations that are not (directly or indirectly) connected to a CORS in the MYCS. For passive stations meeting these criteria, NGS intends to provide NAD 83(2011) epoch coordinates everywhere that is appropriate and can be determined accurately with respect to the MYCS. This will include the conterminous US (CONUS) and Alaska, and it may include other locations outside CONUS as well. The decision as to what additional areas to include will be made during the course of the project. Stations not included in NA2011 will continue to have their positions referenced to the same datum realization used for current survey control prior to NA2011 (as indicated by the datum tag on NGS datasheets).

40 The answer is entirely dependent upon whether an acceptable GNSS survey is ever performed at that passive control mark. For non-gnss (i.e., classically determined) control, the most accurate way to determine coordinates consistent with a modern realization of NAD 83 is to resurvey it using geodetic quality GNSS data. The intended use of this position will determine whether an OPUS solution is sufficient or if a complete GNSS survey submitted to NGS for publication is required.

41 First, consult with NGS through the appropriate personnel or NGS headquarters personnel to ensure your project meets NGS requirements for projects performed during this time frame. When performing the constrained adjustments, unless advised differently by NGS personnel, hold NAD 83(NSRS2007) coordinates for all published passive control and NAD 83(CORS96) coordinates for all CORS in the survey. The same approach for constraining a survey should also be used for projects submitted to NGS that will be included in NA2011 (i.e., before the cut-off date).

42 Yes, those stations will have network and local accuracies computed and published along with the NAD 83(2011) epoch coordinates. As with the NA2011 project itself, these accuracies will be provided in centimeters, and at the 95% confidence level in accordance with the Federal Geographic Data Committee (FGDC) Geospatial Positioning Accuracy Standards, Part 2

43 Based on the MYCS results, the average expected change is about 2 cm horizontally and 1 cm vertically (i.e., ellipsoid height). However, these changes especially the horizontal changes vary significantly. In addition, the largest part of the horizontal change is due to time difference (velocity), especially in tectonically active areas, such as California; when brought to a common time ( ), the average horizontal change decreases to 0.2 cm. A list of coordinate changes, from NAD 83(NSRS2007) epoch to NAD 83(2011) epoch will be provided to the public.

44 For the purposes of transforming the official coordinates of each geodetic control point, NGS will not create a transformation model. An interpolative transformation tool, like NADCON, functions only to apply gross consistent regional shifts to entire areas. NGS will certainly examine the shifts in coordinates for such behavior, but the shifts in going to NAD 83(2011) from NAD 83(NSRS2007) are not expected to significantly exceed the formal errors of those shifts, nor are they expected to all move in one consistent direction regionally. NGS does not endorse the idea of applying a simple interpolative tool to all surveys and maps in a region, as they each will have their own unique connections to surrounding geodetic control. Although NGS will look at all possibilities, there is already compelling evidence that a singular transformed dataset will have very limited applications, and may actually be highly misleading. This is especially the case as the size of the area and required spatial accuracy increase.

45 Good agreement with IGS type means Pending approval from International GNSS Service (IGS) ION GNSS /23/

46 RESULTS

47 Diagram shows plots of average error for 5 points constrained for each of the three realizations. The MYCS coordinates fit the baselines observed much better than the other two.

48 OPUS-net info. From Dr. Neil Weston OPUS-Static U.S. CORS Network Fixed IGS ephemerides Computes independent double differenced baseline solutions between the unknown and 3 CORS Relative antenna models Phase ambiguity integer fixing Relative troposphere modeling ITRF2000 reference frame Average position solution Peak Peak error reported OPUS-Net U.S. CORS Network & IGS Global Network Network approach Consists of 3 nearby CORS + up to 12 CGPS from global IGS network Absolute antenna models SV & ground Ocean tidal loading model Satellite weighting Relative troposphere modeling ITRF2008 reference frame Weighted least squares adjustment Weighted mean and standard deviations reported at 95%

49 WHAT ABOUT THE WSRN?

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52 HTDP v 3.1

53 The epoch is the date associated with the coordinates of a control station. An epoch is a necessary part of a complete datum or reference frame name because coordinates can change with time (i.e., they may have non-zero velocities relative to some chosen, stable coordinate reference). For NA2011, the positions will be referenced to midnight January 1 of 2010 (epoch ). NGS has provided epoch dates for CORS and related products (such as OPUS) for many years, and for passive marks included in the 2007 national readjustment. This practice will continue for NA2011, and it will become more prevalent and consistent throughout NGS. Typically the epoch date is displayed with two decimal places. Users should be aware that if the velocity of a station is known, then its position can be computed at different epochs; thus one datum tag can have multiple epochs. However, the accuracy of the computed position will depend on the accuracy of the velocity, which varies by station and location. Epoch dates on some stations may also change without changing the datum tag if a local episodic event (such as an earthquake) occurs that requires a local adjustment to determine new positions. In summary, epoch dates are needed to accommodate the precision of GNSS measurements and to recognize the dynamic nature of the Earth and its effect on coordinates.

54 Interactively estimate displacements between two dates. Individual points entered interactively or Points on a specified grid Select NAD83(CORS96) or NAD83(NSRS2007) Select the dot for Deci-year format

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57 GRAVITY - GEOID12

58 New hybrid geoid model (likely GEOID12 ) Use NAD 83(2011) epoch ellipsoid heights on NAVD 88 benchmarks Might also use OPUS-Database results on NAVD 88 BMs May perform national vertical adjustment Constrain vertically to NAVD 88 benchmarks Perform as simultaneous nationwide adjustment GNSS-derived orthometric heights NAD 83(2011) ellipsoid heights with GEOID12 NOT a readjustment of NAVD 88 leveling

59 The GPS era brought fast, accurate ellipsoid heights naturally this drove a desire for fast, accurate orthometric heights 1-2 cm accuracy is needed Leveling the country can not be done again Too costly in time and money Leveling yields cross-country error build-up Leveling requires leaving behind marks Bulldozers and crustal motion do their worst

60 Yes, a new hybrid geoid model (GEOID12) will be produced. Preliminary activities in this regard are currently underway. Development of this model requires completion of NA2011 first; hence it cannot be delivered coincidentally with NA2011 results. As is obvious from the model name, NGS expects to deliver the model in As with NA2011, completion of the project will be determined by meeting quality and completeness criteria.

61 Possibly. NGS is currently investigating the need and feasibility of performing a nationwide vertical adjustment of all GNSS-derived orthometric heights in the NSRS. If performed, the GNSS-derived orthometric heights determined for all stations in the vertical adjustment will be consistent with NAD 83(2011) epoch and GEOID12, and they will be referenced to the North American Vertical Datum of 1988 (NAVD 88).

62 SCHEDULE

63 December 14, Finalize modified version of ADJUST and associated project adjustment user guidelines. January 2, SDD performs IDB load. o Final NAD 83(2011) epoch adjusted coordinates and accuracies for passive marks o Final NAD 83(2011) epoch adjusted coordinates and accuracies for CORS January 13, Determine final constrained NAD 83(PA11) and (MA2011) epoch adjusted coordinates (i.e., referenced to Pacific and Mariana tectonic plates) o Delivered to SSD and loaded into NGSIDB o Provide to Geoid Team to develop GEOID12 for Hawaii, American Samoa, Guam, and CNMI.

64 January 31, NA 2011 final report submitted. o Posted to NA2011 web page, o Public announcement that adjustment is entirely complete o Project closeout. o NOTE: Loading of projects submitted after August 31, 2011 cutoff date will continue beyond project closeout date if necessary. February 15, 2012?. Projected delivery date for release of GEOID12 and publication of NAD 83(2011) epoch: coordinates. The release date of GEOID12 is assumed, for the purposes here, to be February 15, 2012, but could easily vary from that date. Additionally, if there is a significant delay in the release of GEOID12 it may be decided to release data sheets with NAD 83(2011) epoch coordinates prior to delivery of GEOID12. o Public Announcement that NAD 83(2011) epoch 2010:00 data sheets are available o Formal announcement submitted for publication in Federal Register

65 April 15, Cutoff date for projects constrained to NAD 83 (NSRS2007). Note this date is tentative as it is actually determined as two months from release of GEOID12 and the release of data sheets with NAD 83(2011) epoch coordinates.

66 WSRN Primary (New) Server will Operate in NAD 2011 Beginning June 2011 Secondary (Legacy) Server will continue to Operate in NAD 83 CORS 96 Epoch for at least one year (likely indefinitely)