1. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Continuously Operating Reference Stations Presented by: Miranda Chin NOAA’s National Geodetic Survey In cooperation with: CGSIC Montpelier, Vermont August 12, 2003

2. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Continuously Operating Reference Stations (CORS) What? Why? OPUS-Online Positioning User Service

3. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Continuously Operating Reference Stations

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

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

6. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Local CORS

7. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS OVERVIEW National CORS Network Cooperative CORS Network Combo CORS

8. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey National CORS Network Network contained over 400 stations as of July 2003 Growing at rate of 6 sites per month Provides code range (C/A, P1, P2) and carrier phase observations (L1, L2) Provides meteorological data at some sites Designed to meet requirements for –High Accuracy Static & Kinematic Positioning –Geophysics / Crustal Motion –Meteorology / Water Vapor in Atmosphere –Space Weather / Free Electrons in Ionosphere

9. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey National CORS Network (continued) National CORS data transferred to NOAA’s National Geodetic Survey in Silver Spring, MD GPS and “met” data converted to RINEX format Data made available to public via: –World Wide Web –File transfer protocol Currently 9 years of CORS data are online for immediate access Parallel CORS Data Site being established at NOAA’s National Geophysical Data Center in Boulder, CO

10. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Cooperative CORS Network GPS base stations whose data are freely disseminated by cooperating organizations NGS provides link from its web site to that of each cooperating organization Site coordinates must be consistent with the National Spatial Reference System

11. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey National CORS & Cooperative CORS - antenna position re-computed every 30 days or less - antenna position re-computed everyday - Minimum 7 days’ data online at the participant’s web site - All data are permanently archived at NOAA - NOAA web site provides a link to the participant’s web page - Data are available online from NOAA via the Internet - Station operates at least 8hrs/day; 5days/week - Station commits to a long-term and continuous operation Cooperative CORSNational CORS

12. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey COMBO CORS The term “Combo CORS” designates a station whose GPS data is distributed both by NOAA’s National Geodetic Survey and by a cooperating organization. Such accessibility to CORS data is highly desirable.

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

14. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey aaaaaaaaaaaaaaaa CORS Partners: Federal Federal Highway Administration Federal Railway Administration Federal Aviation Administration Forecast Systems Laboratory National Geophysical Data Center NASA US Geological Survey US Army Corps of Engineers US Air Force US Naval Observatory

15. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS Partners: States

16. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS Partners: Scientific PANGA BARD SCIGN BARGN EBRY BAYONET International GPS Service (IGS) University Navstar Consortium (UNAVCO) Scripps Orbit & Permanent Array Center Plate Boundary Observatory SuomiNet

17. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS Partners: International Guatemala El Salvador Honduras Nicaragua Mexico Jamaica Canada International Earth Rotation Service (IERS) International GPS Service (IGS)

18. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS Partners: Private Industry “ If you want to see where GPS is going, then keep your eye on the GPS manufacturers.” Bill Strange Former Manager National CORS Program

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

20. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Stations with Meteorological Sensors Forecast Systems Laboratory

21. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS (cont.) Why CORS?

22. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey The National Spatial Reference System (NSRS) is a consistent national coordinate system that specifies latitude, longitude, height, scale, gravity, and orientation throughout the Nation, as well as how these values change with time. NATIONAL SPATIAL REFERENCE SYSTEMS

23. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey NSRS (GEODETIC REFERENCE FRAME) “A geodetic reference framework forms the spatial foundation for the creation of any Land-Information System (LIS).” National Research Counsel Procedures and Standards for a Multipurpose Cadastre (1983, p. 20).

24. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey ACCURATE -- cm accuracy on a global scale MULTIPURPOSE -- Supports Geodesy, Geophysics, Land Surveying, Navigation, Mapping, Charting and GIS activities ACTIVE -- Accessible through Continuously Operating Reference Stations (CORS) and derived products INTEGRATED -- Related to International services and standards (e.g. International Earth Rotation Service, International GPS Service etc.) NATIONAL SPATIAL REFERENCE SYSTEM

25. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey IMPROVING POSITIONAL ACCURACY REFERENCE TIME NETWORK LOCAL FRAME SPAN ACCURACY ACCURACY NAD 27 1927-1986 10 Meters First-Order (1 part in 0.1 million) NAD 83 1986-1990 1 Meter First-Order (1 part in 0.1 million) HARN 1987-1997 0.1 Meter B-Order (1 part in 1 million) A-Order (1 part in 10 million) 0.02 Meter - Horizontal 0.04 Meter - Ellipsoid Height CORS 1994 -

26. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey VCAP Published Coordinates-ARP ITRF00 POSITION (EPOCH 1997.0) Published by the IERS in Mar. 2001. X = 1369550.378 m latitude = 44 15 43.13960 N Y = -4365534.838 m longitude = 072 34 56.56028 W Z = 4429096.685 m ellipsoid height = 159.387 m ITRF00 VELOCITY Published by the IERS in Mar. 2001. VX = -0.0153 m/yr northward = 0.0039 m/yr VY = -0.0050 m/yr eastward = -0.0161 m/yr VZ = 0.0056 m/yr upward = 0.0040 m/yr

27. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey VCAP Published Coordinates-ARP (cont.) NAD_83 POSITION (EPOCH 2002.0) Transformed from ITRF00 (epoch 1997.0) position in Mar. 2002. | X = 1369550.939 m latitude = 44 15 43.10706 N Y = -4365536.278 m longitude = 072 34 56.55559 W Z = 4429096.786 m ellipsoid height = 160.561 m NAD_83 VELOCITY Transformed from ITRF00 velocity in Mar. 2002. VX = 0.0025 m/yr northward = -0.0014 m/yr VY = -0.0031 m/yr eastward = 0.0015 m/yr VZ = 0.0016 m/yr upward = 0.0038 m/yr

28. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey VCAP Published Coordinates-L1 ITRF00 POSITION (EPOCH 1997.0) Published by the IERS in Mar. 2001. X = 1369550.393 m latitude = 44 15 43.13960 N Y = -4365534.889 m longitude = 072 34 56.56031 W Z = 4429096.737 m ellipsoid height = 159.461 m The ITRF00 VELOCITY of the L1 PC is the same as that for the ARP.

29. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey VCAP Published Coordinates-L1 (cont.) NAD_83 POSITION (EPOCH 2002.0) Transformed from ITRF00 (epoch 1997.0) position in Mar. 2002. X = 1369550.954 m latitude = 44 15 43.10706 N Y = -4365536.329 m longitude = 072 34 56.55562 W Z = 4429096.837 m ellipsoid height = 160.636 m

30. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Data Quality Check-60 days Time Series

31. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey CORS ADVANTAGES 3-dimensional (Lat., Long., & Ellipsoid Ht. or X, Y, & Z) Eliminates control points reconnaissance (time and money). Eliminates needing people and equipment at a control points. Direct tie to National Spatial Reference System (NSRS). CORS positions are of the highest accuracy. CORS positions and velocities are available in both NAD 83 and ITRF coordinate systems. CORS positions are continuously monitored and will be updated if the site moves (2cm horizontal; 4cm vertical.)

32. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Common Question CORS GPS hardware differs from our GPS hardware. Do we have to use only CORS with the same hardware?

33. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey OPUS Online Positioning User Service http://www.ngs.noaa.gov/OPUS/ opus@ngs.noaa.gov

34. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHAT IS OPUS? On-line Positioning User Service Provide GPS users faster & easier access to the National Spatial Reference System (NSRS)

35. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW DOES OPUS WORK? Submit RINEX file through NGS web page Processed automatically with NGS computers & software With respect to 3 suitable National CORS Solution via email (usually in minutes)

36. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey OPUS USES 3 CORS SITES

37. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW DO I USE OPUS? 1 - Enter your email address 2 - Enter/Select RINEX file 3 - Select antenna type from menu 4 - Enter antenna height in meters (defaults to ARP) 7 - Upload File Check your email (usually only takes a few minutes) Go to OPUS web page www.ngs.noaa.gov/OPUS 5 - Optional:State Plane Coordinates 6 - Select up to 3 base stations (optional)

38. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHAT ARE SOME OPUS GUIDELINES? Must submit dual-frequency (L1/L2) data Must submit at least 1-hr of data No kinematic/Rapid Static No Glonass Correct vertical requires: antenna type antenna height

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

40. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey GETTING TO OPUS

41. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey OPUS Web Page

42. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey OPUS - Select Reference Site(s)

43. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW IS THE ANTENNA HEIGHT MEASURED? ARP MARK The height is measured vertically (NOT the slant height) from the mark to the ARP of the antenna. The height is measured in meters. The ARP is almost always the center of the bottom-most, permanently attached, surface of the antenna. See GPS Antenna Calibration for photo’s and diagrams that show where the ARP is on most antennas: http://www.ngs.noaa.gov/ANTCAL / If the default height of 0.0000 is entered, OPUS will return the position of the ARP.

44. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHY DO I NEED THE ANTENNA TYPE? The antenna phase centers are located somewhere around here. The Antenna Reference Point (ARP) is almost always located in the center of the bottom surface of the antenna. The antenna offsets are the distance between the phase centers and the ARP If the user selects NONE as the antenna type, the offsets are set to 0.000 and the antenna phase center becomes the reference You do not need to know these offsets. They are passed to the processing software through the antenna type Incorrect or missing antenna type  big vertical errors

45. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Antenna Calibration Facility in Corbin, Virginia

46. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Note that SV elevation and varying phase patterns affect signal interpretation differently........................ SV 14 SV 20 Antenna Type A Antenna Type B Antenna Phase Center Variation

47. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey........................ SV 14 SV 20 Antenna Type A Antenna Type B Different Phase Patterns Note that SV elevation and varying phase patterns affect signal interpretation differently Antenna Phase Center Variation

48. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey ELECTRONIC PHASE CENTER Elevation Angle (deg.) Phase Center Variation (mm)

49. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW ARE OPUS POSITIONS COMPUTED? NGS PAGES software Ionosphere free Tropospheric scale height adjusted Fixed ambiguities Average solution to 3 suitable CORS ITRF and NAD83 positions returned

50. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHAT DOES OPUS OUTPUT LOOK LIKE?

51. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey READING OPUS OUTPUT (input) The version of the PAGES software used for processing The ephemeris used (OPUS will use the best available): “igs” final post-fit orbit-better than 5 cm (14 days wait) “igr” rapid post-fit orbit-better than 10 cm (2 days wait) “igu” ultra-rapid predicted orbit-better than 25 cm (available immediately) The antenna name and antenna reference point height you entered

52. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey READING OPUS OUTPUT (process results) Start/end dates/times of your file Ratio and % of observations used in solution Ratio and % of fixed/total ambiguities Overall RMS of the solution

53. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey Reference Frames & Epoch Date READING OPUS OUTPUT (coordinates) Independent NAD83 & ITRF solutions Peak to peak error is the difference between max and min error for individual solutions Peak to peak error may differ between NAD and ITRF solutions and are usually the worst in the up component Orthometric ht. is based on current geoid model

54. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey READING OPUS OUTPUT (coordinates) Universal Transverse Mercator (UTM) coordinates State Plane coordinates are given (if requested) US National Grid

55. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey READING OPUS OUTPUT (control) Disclaimer Base Stations used in positioning The closest published station listed in the NGS IDB

56. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHAT IS A GOOD SOLUTION? No hard rules - only guidelines Make sure antenna type and antenna height are correct Review statistics should use 90% or more of your observations at least 50% of the ambiguities should be fixed overall RMS should seldom exceed 3.0 cm peak to peak should seldom exceed 5.0 cm

57. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW CAN I IMPROVE MY RESULTS? The best way to get more accurate results is to observe longer sessions Data sets of at least four hours have been shown to produce more reliable results

58. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey HOW DO I GET HELP? First use the Links on the OPUS page Submit specific questions at OPUS web page http://www.ngs.noaa.gov/OPUS/ guidelines for successful use description of output description of processing techniques detailed discussions of guidelines

59. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey WHAT CHANGES ARE PLANNED IN THE FUTURE? Inclusion of Cooperative CORS in the base station selection process Single frequency data processing is being considered Better treatment of RINEX-2 header errors is being implemented. Some translators are not compliant with the RINEX-2 standard

60. Positioning America for the Future NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION National Ocean Service National Geodetic Survey QUESTIONS? http://www.ngs.noaa.gov/OPUS/ opus@ngs.noaa.gov