1. Progress toward the Geopotential Reference Frame Dru Smith Dan Roman Vicki Childers 45 minutes April 13, 20152015 Geospatial Summit1

2. Outline Background Terminology What does “done” look like? – Spoiler alert: there are 5 components… Getting to “done” – Spoiler alert: we need 12 “things” to exist… Progress toward completion What comes after “done”? April 13, 20152015 Geospatial Summit2

3. Background What’s being replaced: HorizontalVertical – NAD 83(2011) – NAD 83(PA11) – NAD 83(MA11) April 13, 20152015 Geospatial Summit3 – NAVD 88 – PRVD 02 – VIVD09 – ASVD02 – NMVD03 – GUVD04 – IGLD 85 Latitude Longitude Ellipsoid Height State Plane Coordinates Heights

4. Terminology Horizontal Datum – Geometric Reference Frame Geocentric X, Y, Z Latitude, Longitude, Ellipsoid Height Vertical Datum – Geopotential Reference Frame Geoid undulation Orthometric height Gravity Deflection of the Vertical April 13, 20152015 Geospatial Summit4

5. What does “done” look like? 1 of 5 April 13, 20152015 Geospatial Summit5 New Geometric Reference Frame @ survey epoch  =38° 42’ 13.777418” =073° 17’ 46.70141” h=146.422 m New Geopotential Reference Frame @ survey epoch H=183.222m H=186.202m Dyn 1: This version of OPUS exists

6. What does “done” look like? 2 of 5 April 13, 20152015 Geospatial Summit6  =38° 42’ 13.74020” =073° 17’ 46.73029” h=147.034 m NAD 83(2011)* epoch 2010.00 New Geometric Reference Frame epoch 2022.00 2: This new transformation tool exists  =38° 42’ 13.777418” =073° 17’ 46.70141” h=146.422 m * Or NAD 83(PA11) or NAD 83(MA11)

7. What does “done” look like? 3 of 5 April 13, 20152015 Geospatial Summit7 NAVD 88, and etc* New Geopotential Reference Frame, epoch 2022.00 3: This new transformation tool exists H=586.444m * Helmert Orthometric Heights in NAVD 88. Normal Orthometric Heights in PRVD02, ASVD02, NMVD03, GUVD04, VIVD09 All, “as published in 2022.00”. H=587.133m

8. What does “done” look like? 4 of 5 April 13, 20152015 Geospatial Summit8 IGLD 85 New Geopotential Reference Frame, epoch 2022.00 4: This new transformation tool exists H=843.162m Dyn H=842.773m Dyn

9. What does “done” look like? 5 of 5 April 13, 20152015 Geospatial Summit9 5: The FGCS has voted to approve the new frames

10. “Done” : Summary A.OPUS: All basic coordinates in new frames B.Tool: Lat/Lon/Eht to new geometric C.Tool: Ortho heights to new geopotential D.Tool: Dynamic heights to new geopotential E.FGCS approval April 13, 20152015 Geospatial Summit10

11. Getting to “done” April 13, 20152015 Geospatial Summit11 A.K.A. What must exist to get to “done”?

12. Getting to “done” 1: IGSxx = The most recent IGS reference frame prior to 2022 April 13, 20152015 Geospatial Summit12

13. Getting to “done” 2: A complete, self-consistent airborne-based gravity* data set over the USA and territories, at epoch 2022.0, in IGSxx. * “gravity” will mean “vertical acceleration of gravity” unless stated otherwise April 13, 20152015 Geospatial Summit13 g

14. Getting to “done” 3: A terrestrial gravity data set over the USA and territories, consistent with #2, at epoch 2022.0 April 13, 20152015 Geospatial Summit14

15. Getting to “done” 4: A DEM of ellipsoid heights in IGSxx/GRS-80 at 30 meter resolution, for epoch 2022.0, over the USA and territories April 13, 20152015 Geospatial Summit15

16. Getting to “done” 5: Three final geoid models (North America, Guam/CNMI and American Samoa), consistent with #2, #3 and #4, each centered at the center of IGSxx April 13, 20152015 Geospatial Summit16

17. Getting to “done” 6: Three geoid secular velocity models, as companions to #5 April 13, 20152015 Geospatial Summit17 cm / yr

18. Getting to “done” 7: GNSS positioning in all OPUS products in IGSxx at the epoch of the survey April 13, 20152015 Geospatial Summit18 IGSxx @ survey epoch  =38° 42’ 13.777418” =073° 17’ 46.70141” h=146.422 m

19. Getting to “done” 8: Software to interpolate geoid undulations April 13, 20152015 Geospatial Summit19

20. Getting to “done” 9: Software to compute dynamic heights from ellipsoid heights, geoid undulations and surface gravity April 13, 20152015 Geospatial Summit20 Dyn hNghNg H

21. Getting to “done” 10: GNSS survey on NAD 83 marks April 13, 20152015 Geospatial Summit21 ,,h in NAD 83(2011)* ~”thousands” * Or NAD 83(PA11) or NAD 83(MA11) Thankfully the CORS are the first 2000 such points with both “recent GNSS data” and “published NAD 83 coordinates”

22. Getting to “done” 11: GNSS survey on NAVD 88 marks April 13, 20152015 Geospatial Summit22 H in NAVD 88* ~”thousands” * Or PRVD02, ASVD02, NMVD03, GUVD04, VIVD09

23. Getting to “done” 12: GNSS survey on IGLD 85 marks April 13, 20152015 Geospatial Summit23 H in IGLD 85 ~”hundreds” Dyn

24. Getting to “done”: Summary 1)IGSxx 2)Airborne Gravity 3)Surface Gravity 4)DEM 5)3 Geoid models 6)3 Geoid change models April 13, 20152015 Geospatial Summit24 7)OPUS in ITRFxx 8)Interp. software 9)Dyn. Ht software 10)GPS on 83 marks 11)GPS on 88 marks 12)GPS on 85 marks

25. Progress toward completion April 13, 20152015 Geospatial Summit25

26. Progress toward completion: Warning NGS has lost significant expertise in the last few years and has struggled to gain new expertise. Many tasks listed next are in RED, indicating they are are likely to cause failure at 2022 if not corrected quickly. April 13, 20152015 Geospatial Summit26

27. Progress toward completion: #1) IGSxx 1)The creation of each iteration of IGSxx is done under the auspices of the IGS (part of the IERS) 2)NGS participates in and contributes to this process but does not control it 3)In the absence of any future IGSxx’s, NGS will use IGS08 April 13, 20152015 Geospatial Summit27

28. Progress toward completion: #2) Airborne Gravity 1)GRAV-D is on track for a 2021 completion 42% done as of today 2)Re-processing into new IGSxx’s is time consuming. May require substantial contract work immediately prior to 2022. 3)Decision about how to move old surveys into epoch 2022.0 is being hotly debated in NGS April 13, 20152015 Geospatial Summit28 g

29. Progress toward completion: #3) Surface Gravity 1)NGS has over 2 million surface gravity points at epochs spanning a century 2)No comprehensive effort is currently underway to adjust these data to be consistent with airborne gravity. April 13, 20152015 Geospatial Summit29

30. Progress toward completion: #4) DEM 1)A DEM exists from SRTM data covering all needed areas at the correct resolution 2)The DEM epoch is 2000 3)Other DEMs (TerraSar-X, etc) may need to be adopted to achieve a DEM nearer to the 2022.0 epoch 4)Transformation of the final DEM will still need to occur to be in IGSxx April 13, 20152015 Geospatial Summit30

31. Progress toward completion: #5) Geoid Models 1)Experimental geoid models have been created with airborne gravity since 2011, and regularly since 2014 2)Geoid Slope Validation Surveys have begun (2011) to prove the accuracy of a gravimetric geoid model – 2011: 1 cm proven! – 2014: Being analyzed – 2016: Line Investigation begins next month 3)An agreement with Canada on W0 exists. April 13, 20152015 Geospatial Summit31

32. Progress toward completion: #5) Geoid Models 4)NGS does not yet have internal agreement about the proper and final method of combining all gravimetric data sources into a geoid model. 5)The plan to ensure Canada and Mexico are in agreement upon final data sets and final computational methods to arrive at a mutually acceptable North American geoid model in 2022 is not yet complete. April 13, 20152015 Geospatial Summit32

33. Progress toward completion: #6) Geoid Velocity Models 1)Satellite missions, especially GRACE, currently provide a secular view of geoid shape change through time 2)NGS has decided that episodic geoid shape changes, such as Earthquakes, will be re-surveyed at a to-be- determined threshold. 3)NGS has decided that periodic geoid change (annual melt/thaw cycles of glaciers) will not be tracked as part of the geoid. April 13, 20152015 Geospatial Summit33

34. Progress toward completion: #6) Geoid Velocity Models 4)The geoid’s size (i.e. its relationship to rising sea level) is being hotly debated at NGS. 5)No plan exists at NGS for how we will monitor secular geoid change in the absence of satellite missions. April 13, 20152015 Geospatial Summit34

35. Progress toward completion: #7) OPUS in IGSxx This has been covered in the “Progress toward a new Geometric Reference Frame” talk. April 13, 20152015 Geospatial Summit35  h

36. Progress toward completion: #8) Interpolation Software 1)NGS has many products and services that require interpolation from either random points or off of a grid. 2)Many of the historic interpolators presumed computers had little RAM which meant loading less of the grid. This meant ease of use but “step function” errors could occur. Small RAM is less of an issue today and entire geoid grids could easily be loaded in most modern personal computers. 3)NGS must decide which interpolator to install in all products and services April 13, 20152015 Geospatial Summit36

37. Progress toward completion: #9) Dynamic Height Software 1)Dynamic heights in IGLD85 came from geopotential numbers which, in turn, came from surface gravity and field leveling. 2)In the new geopotential reference frame, GNSS based ellipsoid heights, will be converted (via a geoid) into orthometric heights which will then be converted to geopotential numbers using surface gravity which will then, finally, be converted into dynamic heights. No leveling. 3)No resources have yet been allocated to study the accuracies achievable from GNSS-derived dynamic heights, nor to convert that research into a functioning piece of software for customer use. April 13, 20152015 Geospatial Summit37 Dyn hNghNg H

38. Progress toward completion: #10) GPS on NAD 83 points 1)To properly support a transformation tool, any new GNSS on NAD 83 points must occur near enough to 2022 that the IGSxx velocities remain linear (no accelerations or earthquakes) 2)NGS supports a “GPS on BM” campaign annually, which often collect data on joint NAD 83/NAVD 88 points. 3)In order to support the greatest nationwide accuracy, a national GNSS campaign should occur between about 2018 and 2021 April 13, 20152015 Geospatial Summit38

39. Progress toward completion: #11) GPS on NAVD 88 points 1)Similar to #10 2)Thankfully, most “GPS on BM” data are on joint NAD 83/NAVD 88 points. April 13, 20152015 Geospatial Summit39

40. Progress toward completion: #12) GPS on IGLD85 points 1)Similar to #10 and #11, but research mentioned in #9 must occur 2)A joint USA/Canada campaign to survey GPS on as many IGLD85 points as possible should occur near 2021 April 13, 20152015 Geospatial Summit40

41. Progress toward completion: Summary 1)NGS is in critical shortage of geodesists to accomplish all of the tasks needed to have the geopotential reference frame complete by 2022 2)Numerous “nice, but not necessary” tasks have been reduced in priority to make success more likely (like having a gravity or DOV interpolator built into OPUS). April 13, 20152015 Geospatial Summit41

42. What comes after “done”? April 13, 20152015 Geospatial Summit42

43. What comes after “done”? 1)What you’ve seen is the bare minimum for NGS to successfully define, maintain and provide access to a new geopotential reference frame. 2)Other significant tasks remain. With additional resources, they could be accomplished before 2022. Without them, they will not be started until after 2022. April 13, 20152015 Geospatial Summit43

44. Thank You! April 13, 20152015 Geospatial Summit44 http://www.ngs.noaa.gov/datums/newdatums/

45. 1)Coordinates in the new frames will evolve over time, but the transformation tool will only take you to epoch 2022.0. 2)Nothing was said about passive control being published in the new reference frames. 3)OPUS doesn’t yield up other values of interest, like deflections of the vertical, geopotential or acceleration of gravity. April 13, 20152015 Geospatial Summit45 “Done” : What you probably noticed was missing

46. 4)Nothing was mentioned about whether latitude and longitude would be plate fixed 5)Nothing was said about NGS accepting GNSS or leveling or gravity or DOV or traverse surveys in the new geopotential reference frame April 13, 20152015 Geospatial Summit46