Geodetic Positioning Refresher

Transcription

1 Geodetic Positioning Refresher by Joan Yau PhD ABCLS AGM 2016, Kimberley BC

2 Contents Horizontal / Vertical Datums and Epochs used in BC and Canada How do we reference our project coordinates to BC datums Common Data Formats in Surveying Review of Common Terms used in Geodetic Positioning Geodetic Positioning Refresher - p2

3 Horizontal / Vertical Datums and Epochs used in BC and Canada Horizontal Datums and Epochs in BC and Canada What is/are the current datum(s) in BC? Which datum to select? Vertical Datums in BC and Canada How do we tie our project coordinates to BC datum Common Data Formats in Surveying Review of Common Terms used in Geodetic Positioning Geodetic Positioning Refresher - p3

4 Horizontal Datums and Epochs in BC, Canada Geodetic Positioning Refresher - p4

5 Horizontal Datums in North America There are two fundamental horizontal datums in North America: North American Datum 1983 (NAD83) and North American Datum 1927 (NAD27) NAD83 is the current horizontal datum for both Canada and USA. For most applications in surveying, NAD83 is the adopted datum, although some applications are still in NAD27 datum. Geodetic Positioning Refresher - p5

6 Horizontal Datums: Ellipsoids of Our Datums GPS uses WGS84 ellipsoid. Both NAD83 and NAD27 are using different ellipsoids than WGS84. The following table shows the ellipsoid of each horizontal datum in North America and the corresponding geometry (shape) of the ellipsoid. Horizontal Datum Ellipsoid a (semi-major axis) (m) 1/f, f is flattening North American Datum 1927 (NAD27) North American Datum 1983 (NAD83) Clarke ,378, ,698 GRS ,378, ,222 WGS ,378, ,224 With the development of various epochs in the horizontal datums/reference frames in North America, the current horizontal datum/reference frame/epoch in Canada is: Canada: NAD83 CSRS98 epoch , or in long term North American Datum 1983 Canadian Spatial Reference System 1998, Epoch 2002, or in short NAD83 CSRS Geodetic Positioning Refresher - p6

7 Horizontal Datums: Ellipsoid vs Datum Q: What is an Ellipsoid? A: An Ellipsoid is a pure mathematical model defined by 8 parameters. These 8 parameters will define the shape, origin, orientation and zero longitude of this mathematical ellipsoid. Q: What is a Datum? A: A Datum is defined as any numerical or geometrical quantity or set of such quantities which serves as a reference from which to measure other quantities. In other words, a Datum is a Realization of an Ellipsoid. Geodetic Positioning Refresher - p7

8 NAD83 vs NAD27 Although there is no scale change or rotations between NAD83 and NAD27 datums, the shapes of GRS80 and Clarke 1866 are very different, the origins of these two ellipsoids differ by almost 200 m. Normal to the Clarke 1866 Ellipsoid Z NAD27 Z NAD83 UTM North Normal to the GRS 1980 Ellipsoid GRS 1980 Ellipsoid UTM East (x, y, z) or (ϕ, λ, h) X Y Z NAD83 = X Y Z NAD m Y NAD83 Y NAD27 X NAD27 X NAD83 Clark 1866 Ellipsoid In Canada, to transform between NAD82 and NAD27, it is recommended to use National Transformation version 2 (NTv2) from Natural Resources Canada (NRCan). Geodetic Positioning Refresher - p8

9 GRS80 vs WGS84 vs Clarke 1866 GRS80 WGS84 Clarke 1866 Note: Diagram is not to scale and not in correct orientation. Geodetic Positioning Refresher - p9

10 NAD83 vs WGS84 Q: Are NAD83 coordinates and WGS84 coordinates interchangeable? Geodetic Positioning Refresher - p10

11 What is/are the current Horizontal Datum(s) defined by the Provincial and Federal? Geodetic Positioning Refresher - p11

12 Q: How many (current) NAD83 datums in BC? A: a) More than 1. True? b) More than 2. True?? c) More than 3. True??? d) More than 4. True???? e) More than 5. True????? f) More than 6. True?????? Geodetic Positioning Refresher - p12

13 Current Horizontal Datums in BC Horizontal Datum with 2 Epochs defined by the Federal (NRCan) for the Province of BC: Datum: NAD83 CSRS Epochs: for Mainland for Vancouver Island Geodetic Positioning Refresher - p13

14 CACS Stations in BC Geodetic Positioning Refresher - p14

15 CACS Datums and Epochs Coordinates: Geographic Cartesian UTM Geoid: CGG2013 HT2_0 CGG2010 CGG2005 CGG2000 GSD95 GSD91 EGM08 Reference Frame: NAD83(CSRS) ITRF2008 ITRF2005 ITRF2000 ITRF97 ITRF96 ITRF94 ITRF93 ITRF92 ITRF91 ITRF90 ITRF89 ITRF88 Epoch: Epoch of adjustment BC(Vancouver Island), MB, NB, NS, ON, PE, QC, SK AB, BC(mainland), NT, NU, YT NL Select by date Note: NAD83 v3 (1997.0) was adopted in 2000, transformed from ITRF97 (completion of CBN). NAD83 v4 (2002.0) was adopted in 2002, transformed from ITRF2000. NAD83 v6 (2010.0) was adopted in 2012, transformed from ITRF2008/IGS08 Geodetic Positioning Refresher - p15

16 Example of CACS Data Sheet WSLR (Whistler) Geodetic Positioning Refresher - p16

17 Station Coordinate Changes in North and East Over the Last 14 Years (2002 Feb 2 to 2016 Feb 2) HOLB m m WILL m m QUAD m m WSLR m m ALBH m m CHWK m 0.068m DRAO m m Geodetic Positioning Refresher - p17

18 Current Horizontal Datums in BC 4 Horizontal Datums defined by the Province: Provincial Mainland (other than the Greater Vancouver Regional District (GVRD)): Datum: NAD83(CSRS) BC.1 Refresh of 2005 GVRD: Datum: NAD83(CSRS) BC.1.GVRD Refresh of 2005 Northern Vancouver Island (NVI) (North of the Capital Regional District (CRD)): Datum: NAD83(CSRS) BC.1.NVI Refresh of 2005 CRD: Datum: NAD83(CSRS) BC.1.CRD Re-fresh of 2000 Geodetic Positioning Refresher - p18

19 BCACS Map BCPG GCM BCES BCVC Geodetic Positioning Refresher - p19

20 Horizontal Datums in BC 4 Horizontal Datums in BC: Provincial Mainland (other than the Greater Vancouver Regional District (GVRD)): Datum: NAD83(CSRS) BC.1 Refresh of 2005 GVRD: Datum: NAD83(CSRS) BC.1.GVRD Refresh of 2005 Northern Vancouver Island (NVI) (North of the Capital Regional District (CRD)): Datum: NAD83(CSRS) BC.1.NVI Refresh of 2005 CRD: Datum: NAD83(CSRS) BC.1.CRD Re-fresh of 2000 Geodetic Positioning Refresher - p20

21 Which Horizontal Datum / Epoch to select for projects in BC? Geodetic Positioning Refresher - p21

22 Which horizontal datum to select? $1,000,000 question? Provincial Federal NAD83(CSRS) BC.1 NAD83(CSRS) BC (mainland) NAD83(CSRS) BC.1.NVI NAD83(CSRS) BC (Vancouver Island) NAD83(CSRS) BC.1.CRD NAD83(CSRS) BC.1.GVRD Geodetic Positioning Refresher - p22

23 Which horizontal datum to select? Depends: On the Location of the project On the Size of the project On the client s needs Availability of reference/starting control points Ideal scenario: Federal and Provincial use the same datum(s) One horizontal datum in BC (or Two: one for the mainland and one for Vancouver Island) Geodetic Positioning Refresher - p23

24 Vertical Datums in Canada Geodetic Positioning Refresher - p24

25 Vertical Datums and Geoid Models in Canada There are two vertical datums in Canada: Vertical Datum Canadian Geodetic Vertical Datum 1928 (CGVD28) Canadian Geodetic Vertical Datum 2013 (CGVD2013) Canadian Vertical Datum 1928 British Columbia (CVD28BC) Canadian Vertical Datum 1928 Greater Vancouver Regional District (CVD28GVRD) Note: CGVD2013 was available since November It is expected both CGVD2013 and CGVD28 vertical datums will co-exist for the next 10 to 20 years. CGVD2013 is using Canadian Gravimetric Geoid model of 2013 (CGG2013) as geoid model. The most common geoid model in CGVD28 is HT2.0. Regional BC Vertical Datum CGVD28GVRD was established in The rest of BC Vertical Datum is CVD28. Geodetic Positioning Refresher - p25

26 CACS Datums and Epochs Coordinates: Geographic Cartesian UTM Geoid: CGG2013 HT2_0 CGG2010 CGG2005 CGG2000 GSD95 GSD91 EGM08 Reference Frame: NAD83(CSRS) ITRF2008 ITRF2005 ITRF2000 ITRF97 ITRF96 ITRF94 ITRF93 ITRF92 ITRF91 ITRF90 ITRF89 ITRF88 Epoch: Epoch of adjustment BC(Vancouver Island), MB, NB, NS, ON, PE, QC, SK AB, BC(mainland), NT, NU, YT NL Select by date Note: CGG2013 Geoid Model is for CGVD2013 Vertical Datum. HT2_0 Geoid Model is for CGVD28 Vertical Datum. Geodetic Positioning Refresher - p26

27 Elevation Changes ( H) between Different Geoid Models (HT 2_0/CGVD28 to CGG2013/CGVD2013) HOLB Elev = 575 m H = m WILL Elev = 1,110 m H = m QUAD Elev = 8 m H = m WSLR Elev = 924 m H = m ALBH Elev = 50 m H = m CHWK Elev = 192 m H = m DRAO Elev = 558 m H = m Geodetic Positioning Refresher - p27

28 Horizontal / Vertical Datums and Epochs used in BC and Canada How do we reference our project coordinates to BC datums? Options to reference our project to BC datum (GNSS) Networks available in BC (Federal, Provincial, Private) and their corresponding comments Processing software available in BC Common Data Formats in Surveying Review of Common Terms used in Geodetic Positioning Geodetic Positioning Refresher - p28

29 Options to reference our project coordinates to BC datums Geodetic Positioning Refresher - p29

30 Options to reference our project to BC datum Use existing geodetic monuments GNSS: Post-Processing, RTK Conventional Survey Instruments (eg total stations, levels) and Methods Astronomic Measurements Use existing GNSS networks: federal, provincial, or private Geodetic Positioning Refresher - p30

31 (GNSS) Networks Available in BC: 1. Federal 2. Provincial 3. Private Networks Geodetic Positioning Refresher - p31

32 Provincial (BCACS) and Federal (CACS) Reference Station Networks in BC BCACS CACS Geodetic Positioning Refresher - p32

33 BCACS / CACS Station Coordinates Can you trust these published coordinates? Geodetic Positioning Refresher - p33

34 Can you trust the published data and/or coordinates? 3 BCACS stations selected: BCVC, BCSS, BCPR 5 days of 24-hr data: 2015 Oct 15, Nov 15, Dec 15, 2016 Jan 15, Feb 15 Published coordinates are compared vs calculated coordinates Geodetic Positioning Refresher - p34

35 Data consistency Day 1: 2015 Oct 15 Day 2: 2015 Nov 15 Day 3: 2015 Dec 15 Day 4: 2016 Jan 15 Day 5: 2016 Feb 15 Geodetic Positioning Refresher - p35

36 Example 1: BCVC (BCACS Vancouver) BCVC (PPP Published) in NAD83 CSRS Epoch Date Duration (hrs) N (m) E (m) Elev (m) Geodetic Positioning Refresher - p36

37 Example 1: BCSS (BCACS Sandspit) BCSS (PPP Published) in NAD83 CSRS Epoch Date Duration (hrs) N (m) E (m) Elev (m) Geodetic Positioning Refresher - p37

38 Example 1: BCSS (BCACS Prince Rupert) BCPR (PPP Published) in NAD83 CSRS Epoch Date Duration (hrs) N (m) E (m) Elev (m) Geodetic Positioning Refresher - p38

39 BCACS / CACS - Remarks Can you trust these published coordinates? Build in redundancies in your network. Get familiar with the reference stations. Watch out for the many datums/epochs available in CACS. Watch out for the station coordinates in RINEX. Watch out for the antenna types in CACS and BCACS. Geodetic Positioning Refresher - p39

40 Private Reference Station Networks in BC Geodetic Positioning Refresher - p40

41 Private Networks - Remarks Watch out for the datums/epochs in the private networks. How accurate are the reference station coordinates? Datums? Epochs? In RTK: Are you using the correct reference station? Watch out for the antenna types in private networks. Geodetic Positioning Refresher - p41

42 Processing software available in BC: Precise Point Positioning (PPP) from NRCan Geodetic Positioning Refresher - p42

43 PPP User Interface Horizontal Datum & Epoch Vertical Datum & Geoid Model Geodetic Positioning Refresher - p43

44 PPP Accuracies vs Time CACS station CHWK (PPP Published) on 2016 Feb 2 in NAD83 CSRS Epoch and CGVD2013 Duration (hrs) N (m) E (m) Elev (m) < 2 cm in Hz < 3 cm in Vt Geodetic Positioning Refresher - p44

45 PPP Accuracies vs Time CACS station ALBH (PPP Published) on 2016 Feb 2 in NAD83 CSRS Epoch and CGVD2013 Duration (hrs) N (m) E (m) Elev (m) < 2 cm in Hz < 3 cm in Vt Geodetic Positioning Refresher - p45

46 PPP Accuracies vs Time CACS station WILL (PPP Published) on 2016 Feb 2 in NAD83 CSRS Epoch and CGVD2013 Duration (hrs) N (m) E (m) Elev (m) < 2 cm in Hz < 3 cm in Vt Geodetic Positioning Refresher - p46

47 PPP - Remarks The result is returned between 2 30 minutes after the data is submitted. In general, it takes ~ 2 hours of dual frequency GNSS data to achieve better than 2 cm in horizontal and 3 cm in vertical. Watch out for the many epochs available in PPP. PPP does not allow for antenna type file. Geodetic Positioning Refresher - p47

48 Horizontal / Vertical Datums and Epochs used in BC and Canada How do we reference our project coordinates to BC datums? Common Data Formats in Surveying GNSS, Map, Ground, Local Questions? Remarks? Review of Common Terms used in Geodetic Positioning Geodetic Positioning Refresher - p48

49 Common Formats in Geodetic Positioning 1. NAD83 CSRS Geodetic: Latitude, Longitude, Ellipsoid Height A unique system 2. Map Coordinates: Grid: Northing, Easting, Elevation 5 UTM zones in BC (zones 7 11) Various geoid models 3. Ground Coordinates derived from Map: Grid: Northing, Easting, Elevation Depends on Elevation Scale Factor in project GGGGGGGGGGdd NN = GGGGGGGGGGdd EE = NN UUUUMM AAAAAA. CCCCCCCCCCCCCCCC SS. FF. + NN ssssssssss EE UUUUMM AAAAAA. CCCCCCCCCCCCCCCC SS. FF. + EE ssssssssss 4. Local Coordinates: Grid: Northing, Easting, Elevation Arbitrary systems Elevation Geodetic Positioning Refresher - p49

50 Questions? Questions?? More Questions??? What coordinate format we need to provide? What format(s)to archive? Other than measurements or adjusted results, what other information we need to archive? What do we do when we cross over different UTM zones? Geodetic Positioning Refresher - p50

51 Horizontal / Vertical Datums and Epochs used in BC and Canada How do we reference our project coordinates to BC datums? Common Data Formats in Surveying Review of Common Terms used in Geodetic Positioning North: Geodetic, Grid, Magnetic, Astronomic Orientation: Azimuth, Bearing Geodetic Positioning Refresher - p51

52 Norths: Grid, Geodetic, Magnetic 90 N Grid North Geodetic North Grid North Geodetic North Geodetic North Grid North 60 N 30 N Magnetic North Magnetic North Geodetic North Magnetic North Grid North Magnetic North 0 N Geodetic Positioning Refresher - p52

53 Relationships of Norths: Grid vs Geodetic vs Magnetic Geodetic North Grid North Magnetic North Convergence Angle Grid (Magnetic) Declination (Geodetic Magnetic) Declination Geodetic Positioning Refresher - p53

54 Orientation Geodetic Azimuths (α) vs Grid Bearings (β) 90 N Grid North Grid North Geodetic North 60 N 30 N C β CD D β DC Geodetic North B α BA β CD = β DC ± 180 α AB α AB α BA ± N A Geodetic Positioning Refresher - p54

55 WGS84 Coordinates Geodetic and Cartesian Geodetic Coordinates: Latitude, φ Longitude, λ Ellipsoid height, h Z axis Cartesian Coordinates: (X, Y, Z) P Z φ Y axis λ Y X axis Geodetic Positioning Refresher - p55

56 60You 50 are Done 20 10!! η Geodetic Positioning Refresher - p56

57 Deflection of the Vertical, η (eta), in the E/W direction Astronomic Longitude E/W WGS84 Geodetic Longitude E/W W E ~5.3 or ~102m Geodetic Positioning Refresher - p57

58 Prime Meridian (Greenwich) vs WGS84 Zero Longitude Z axis P X Z φ Y axis λ Y X axis Geodetic Positioning Refresher - p58