Utilizing A GNSS Network Solution for Utility Applications

Transcription

1 Utilizing A GNSS Network Solution for Utility Applications David Newcomer, PE, PLS GPServ, Inc. newcomer@ (407)

2 AGENDA Types and accuracies of data collection o Autonomous o Meter + o Sub-meter o Centimeter Methods of data collection o SBAS or DGPS o Broadcast your own o Network Single base Virtual Reference Station (VRS)

3 AGENDA Other data collection concerns o What accuracy do you require? o In what datum do you need your data? o What is the datum of the base station? o What Geoid are you using (Geoids are datum dependent)? Network concerns o What is the datum of the RTN? o What Geoid are you using? A Case Study

4 FOUR METHODS OF POSITIONING 1. Autonomous 3-10 meters 2. Differential 0.5 to 3 meters 3. Static Positioning Sub-centimeter 4. Real Time Kinematic Centimeter

5 GNSS ACCURACIES mm 24.26mm

6 STATIC POSITIONING CORS Stations Point where coordinates are desired

7 GNSS ACCURACY Depends on some variables: Time spent on measurements Design of receiver Relative positions of satellites Use of Differential Techniques

8 Accuracy Three methods of real time positioning: 1. Autonomous 3-10 meters 2. Differential One to five meters Sub-meter 3. Phase Differential Decimeter Centimeter 1-5m 75cm 1cm 3-10m

9 REAL TIME GNSS POSITIONING BASE STATION SET UP UHF RADIO Now you need communication also. THE NEW PART You still require a base station

10 REAL TIME GNSS POSITIONING ROVER SETUP INTERNAL RADIO You still require a rover.

11 REAL TIME POSITIONING From This To This

12 THE THREE BASE STATION OPTIONS FOR RT

13 First Things First o What accuracy do you need? o Of what accuracy is the receiver (sensor) capable? o What will it take to get the accuracy you need from the receiver? (RMS) Part of the benefits of using an RTN over single base RTK Limited/Reduced ppm error UNDERSTAND THE ROVER SPECIFICATIONS

14 TO USE MONUMENTS OR NOT, THAT IS THE? In prior years geospatial professionals relied on PASSIVE control such as monuments and benchmarks for tying to a datum. Today there is ACTIVE control in the form of CORS stations. Which one is better? Which one can be more easily maintained? IS PASSIVE CONTROL AS GOOD AS ACTIVE CONTROL?

15 IS ACTIVE CONTROL AS GOOD AS PASSIVE CONTROL? The horizontal control was first established by triangulation.

16 IS ACTIVE CONTROL AS GOOD AS PASSIVE CONTROL? Vertical control was accomplished by leveling using the best instruments and techniques available.

17 IS ACTIVE CONTROL AS GOOD AS PASSIVE CONTROL? 18 FT

18 IS ACTIVE CONTROL AS GOOD AS PASSIVE CONTROL?

19 PASSIVE CONTROL = 35 YEARS OLD

20 MONUMENT MOVEMENT ON THE NORTH AMERICAN PLATE Plate moves at approximately 2.3 cm per year. The plate does not move uniformly. POINT DANIEL Absolute Movement 35 years X 2.3 cm/year = 80.5 cm or approx. 2.5 ft Relative Movement 35 years X.6 cm/year = 21 cm or approx. 8 inches Mean horizontal shift = 0.2 cm (±2 cm) at epoch IS PASSIVE CONTROL AS GOOD AS ACTIVE CONTROL?

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22 Atmosphere Based Ionospheric Delay delay TEC 2 f > 5 km

23 Troposphere Delay

24 RTN FUNCTION Real Time Network software creates an atmospheric delay model from surrounding network station data.

25 NETWORKS IN FLORIDA Trimble FDOT Topcon

26 TOPCON NETWORK

27 TOPCON NETWORK 54 STATIONS AS OF 26 JULY 2016 According to the website: Datum: NAD 83 (NSRS 2007) Horizontal NAVD 88 Vertical NOTE: NSRS 2007 was based on Epoch

28 FDOT NETWORK

29 FDOT NETWORK 97 STATIONS AS OF 26 JULY 2016 DATUMS Horizontal: NAD83 (2011) Epoch Vertical: NAVD 88

30 TRIMBLE NETWORK

31 TRIMBLE NETWORK - FLORIDA

32 TRIMBLE NETWORK - FLORIDA 50 STATIONS AS OF 26 JULY 2016 DATUMS Horizontal: NAD83 (2011) Epoch Vertical: NAVD 88

33 Single Base Data Collection BASELINE

34 VRS Data Flow Reference station data streams back to server through LAN, Internet, or radio links

35 VRS Data Flow Roving receiver sends a NMEA string back to server using cellular modem. Virtual Reference Station position is established. VRS NMEA GGA

36 VRS Data Flow Server uses VRS position to create corrected observables and broadcasts them to the rover VRS

37 VRS Data Flow Rover surveying in normal RTK mode but data is relative to the VRS VRS BASELINE

38 Number of Postions GPServ, Inc. Serving Geospatial Professionals Error in North 32 km Baseline Confidence Level 90 %: < 13 mm 99 %: < 26 mm Error [mm]

39 Number of Positions GPServ, Inc. Serving Geospatial Professionals Error in East 32 km Baseline Error [mm] Confidence Level 90 %: < 9 mm 99 %: < 21 mm

40 Number of Positions GPServ, Inc. Serving Geospatial Professionals Error in Height 32 km Baseline Confidence Level 90 %: < 25 mm 99 %: < 49 mm Error [mm]

41 A (very) brief history of WGS 84 Original realization completed in 1987 Same as original NAD 83 (to within ±1-2 m) WGS 84 (G730) adopted Jan 1994 Aligned with ITRF91 WGS 84 (G873) adopted Sep 1996 Aligned with ITRF94 WGS 84 (G1150) adopted Jan 2002 Aligned with ITRF2000 (at epoch ) WGS 84 (G1674) adopted Feb 2012 Aligned with ITRF2008 (at epoch ) WGS 84 (G1762) adopted Oct 2013 Also aligned with ITRF2008 (at epoch ) 41

42 Which Geoid for Which NAD 83? Current status NAD 83(2011) NAD 83(2007) Geoid12A/12B Geoid09 NAD 83(1996) & CORS96 Geoid03 Geoid99 Geoid96 NAD 83(1992) Geoid93 42

43 New Datums are Coming in 2022! Both a new geometric and a new geopotential (vertical) datum will be released in The realization of the new datums will be through GNSS receivers. NGS will provide the tools to easily transform between the new and old datums. 43

44 Terminology Horizontal Datum Geometric Reference Frame Geocentric X, Y, Z Latitude, Longitude, Ellipsoid Height Vertical Datum Geopotential Reference Frame Gravity Geoid undulation Orthometric height Deflection of the Vertical 44

45 Simplified Concept of NAD 83 vs. ITRF Earth s Surface h NAD83 h ITRF h NAD83 h ITRF varies smoothly by latitude and longitude ITRFxx origin NAD 83 origin 45

46 Case Study Courtesy of Trimble Navigation

47 Case Study Courtesy of Trimble Navigation Fast growing area with new gas lines Asset management is a must As-built locations are important

48 Case Study Courtesy of Trimble Navigation

49 Real Time Kinematic GNSS (RTK) 49

50 RTK vs. RTN Cell technology RTK Easy alignment to the NSRS No ppm (1 ST ORDER) ERROR Extended range Homogeneous Data Easy datum updates Atmospheric errors almost eliminated RTN -Half the equipment or double the production -No monument reconnaissance/ recovery - No set/break down time -No base baby sitting

51 Pitfalls Multipath Datum used by RTN Geoid you use vs. datum of RTN Accuracy required Accuracy of GNSS unit Weather local Weather - space

52 Questions