Integrity Monitoring in a VRS Network Bundesamt für Landestopografie Office fédéral de topographie Ufficio federale di topografia Uffizi federal da topografia Simon Grünig, swisstopo GPSNet User Conference, Munich, May 30-31, 2006
VRS-Monitor 23/05/2006 Folie 2 2000 m
Agenda AGNES Network Swiss Positioning Service (swipos ) Integrity Monitoring in a VRS Network, General Aspects The swisstopo VRS Monitor Measurements with the VRS Monitor Conclusion VRS-Monitor 23/05/2006 Folie 3
AGNES Network Automatisches GPS-Netz Schweiz 30 stations (+ 9 stations from D, A) Mean distance between reference stations: 50 km Stations height distribution: 400-3400 m! Several applications National geodetic survey Science (atmosphere, geodynamics) Swiss Positioning Service VRS-Monitor 23/05/2006 Folie 4
Swipos Swiss Positioning Service swipos-gis/geo RTK-VRS accuracy 1-2 cm access by GSM and GPRS/NTRIP RTCM 3.0 user fee swipos-nav DGPS accuracy 0.5-1 m access by GSM and GPRS/NTRIP RTCM 2.3 free of charge VRS-Monitor 23/05/2006 Folie 5
swipos Business Models strongly increasing number of GPRS/NTRIP users due to lower communication costs compared to classic GSM 80% of users accessing swipos by GPRS/NTRIP, 20% only by GSM classic 2 business models business number (GSM, 0.5 /minute) annual subscription (GPRS/NTRIP, 2000 ) 200 subscribed users ~ 50 occasional users (business number) VRS-Monitor 23/05/2006 Folie 6
Integrity Monitoring in a VRS Network (1) What is integrity? Integrity is the capacity of the system to alert the user within a predefined period of time ( Time to Alert ) whenever the system is not available for the current application. Moreover, integrity is the amount of confidence the user can have in the reliability of this information [1] [1] European Comission (2000), Galileo Definitions Document, GALA-DD092 VRS-Monitor 23/05/2006 Folie 7
Integrity Monitoring in a VRS Network (2) How is quality determined within GPSNet? coordinate monitoring troposphere monitoring network model integrity (iono and geo errors) Comparison (daily / hourly) with post-processing (scientific software Bernese 5.0) NTRIP-Monitor (IP Media Solutions, Gebhard) How is quality of user positioning determined? Rover Integrity??? Development of an VRS-Monitor by swisstopo VRS-Monitor 23/05/2006 Folie 8
Requirements for the VRS Monitor simulation of a typical user at different locations 2 main uses: Integrity Monitoring (permanent) performance assessment (occasional) store raw data compare RTK positions (NMEA-GGA) to a ground truth send an alarm by E-mail or SMS if the alarm limit is reached mobile use waterproof (stored in a box) works in autonomous mode (battery and solar panel) VRS-Monitor 23/05/2006 Folie 9
Architecture VRS Monitor RTCM GPS Trimble 5700 GPS NMEA GGA Raw data GSM GPRS/NTRIP Swipos/GPSNet RTKMON - connects to GPSNet - receives and redirects RTCM - analyses NMEA-GGA - writes statistic files - creates graphics - sends alarms by E-mail/SMS VRS-Monitor GPSBase - stores raw data VRS-Monitor 23/05/2006 Folie 10
Software VRS Monitor, RTKMON VRS-Monitor 23/05/2006 Folie 11
VRS Monitor in use VRS-Monitor 23/05/2006 Folie 12
Measurments with the VRS Monitor simulation of different users permanent, roof swisstopo (1) ideal interpolation (2) extrapolation (3) height difference (4) impact of snow (5) 1 2 4 5 3 VRS-Monitor 23/05/2006 Folie 13
Measurments with the VRS Monitor (1) Permanent, roof swisstopo, 2005 1 East North Horizontal Height Init Offset [mm] 5.0-1.1 5.1 4.3 RMS [mm] 5.4 7.1 8.9 16.5 Initialization time [s] 20.4 Outliers (> 3 cm Horizontal, > 6 cm height) : 1.4% VRS-Monitor 23/05/2006 Folie 14
Measurments with the VRS Monitor (2) Ideal interpolation, Grenchen, 5 Days 2 East North Horizontal Height Init Offset [mm] 6.9 8.0 10.6 14.3 RMS [mm] 5.7 8.0 9.8 16.1 Initialization time [s] 20.8 Outliers (> 3 cm Horizontal, > 6 cm height) : 3.2% VRS-Monitor 23/05/2006 Folie 15
Measurments with the VRS Monitor (3) Extrapolation, Zermatt 5 Days East North Horizontal Height Init Offset [mm] -0.4 3.5 3.5 4.9 RMS [mm] 7.2 3 10.7 12.9 26.6 Initialization time [s] 83.5 Outliers (> 3 cm Horizontal, > 6 cm height) : 18.7 % VRS-Monitor 23/05/2006 Folie 16
Measurments with the VRS Monitor (4) Height difference, Brienz, 3 Days 4 East North Horizontal Height Init Offset [mm] -7.3 6.8 9.9-24.6 RMS [mm] 10.6 17.1 20.1 40.2 Initialization time [s] 46.3 Outliers (> 3 cm Horizontal, > 6 cm height) : 24.1 % VRS-Monitor 23/05/2006 Folie 17
Measurments with the VRS Monitor (5) Impact of snow, San Bernardino, 4. Jan - 20. Feb 2006 AGNES Station SANB cleaned at beginning of test (zero reference), afterwards never cleaned again VRS-Monitor antenna (rover) cleaned after each snowfall connection time of VRS-Monitor 30 min distance between VRS-Monitor and reference 45 m VRS-Monitor 23/05/2006 Folie 18
Measurments with the VRS Monitor (5) Impact of snow, San Bernardino, 4. Jan - 20. Feb 2006 5 East North Horizontal Height Init Offset [mm] 0.5-3.8 3.8 7.4 RMS [mm] 6.9 9.8 12.0 17.8 Initialization time [s] 22.0 Outliers (> 3 cm Horizontal, > 6 cm height) : 5 % VRS-Monitor 23/05/2006 Folie 19
Measurments with the VRS Monitor (5) Impact of snow, San Bernardino, 4. Jan - 20. Feb 2006 VRS-Monitor 23/05/2006 Folie 20
Measurments with the VRS Monitor Summary VRS method (GPSNet) gives good results and is distance independent as long as: no extrapolation occurs no big height difference occurs no other event like snow accumulation or thunderstorm occurs new station in Zermatt built last year to reduce extrapolation integration of other neighbourhood stations still ongoing new station in Bernese Oberland will be built this year to reduce the height problem besides the manual cleaning, other methods exist but have disadvantages automatic cleaning Radomes heating of the antenna etc. VRS-Monitor 23/05/2006 Folie 21
Conclusion VRS Monitor is the answer of swisstopo for Integrity Monitoring and performance assessment Other methods are necessary to ensure a full and reliable Integrity Monitoring Integrity Monitoring is a big issue in the positioning field Time to Alert still high Ideally, Integrity message should be on RTCM 3.0 corrections Within Galileo, Integrity is part of the system definition. What does this mean for positioning services? VRS-Monitor 23/05/2006 Folie 22