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2	RTN OVERLAP – 3 DIFFERENT GNSS VENDORS - PRIVATE SECTOR NETWORKS
3	RTN OVERLAP – DOT & PRIVATE SECTOR
4	RTN OVERLAP – VRS DOT & MAC DOT
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7	"POTENTIAL FUTURE DEVELOPMENTS" POTENTIAL FUTURE DEVELOPMENTS (2005 – 2017?) GPS MODERNIZATION – BLOCK IIF & III GLONASS ENHANCEMENTS (K & M) EUROPEAN UNION - GALILEO CHINA - COMPASS 115+ Satellites Second and Third Civil Frequency - GPS No Signal Encryption - GLONASS & GALILEO More Robust Signal Transmissions Real-Time Unaugmented 1 Meter (or better!) Accuracy
8	FAIRFAX COUNTY, VIRGINIA
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10	GNSS DERIVED HEIGHTS NOS-NGS 58 WITH DRAFT ORTHO GUIDELINES- 0.05 M TO NSRS, 0.02 M LOCAL DGPS – 15 SECONDS, 0.5 TO 2 M OPUS > 4 HRS = 0.02 M (h), 0.05 (H) CORS- SAME AS OPUS OPUS-RS 15 MINUTES =0.10 M SINGLE BASE RTK- “IT DEPENDS!” 5 SECONDS (better than 0.03 M expected) RTN – “IT DEPENDS!” 5 SECONDS ( better than 0.04 M expected)
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13	CLASSICAL REAL TIME POSITIONING PDOP MULTIPATH SATELLITES BASE ACCURACY BASE SECURITY REDUNDANCY, REDUNDANCY, REDUNDANCY PPM – IONO, TROPO MODELS, ORBIT ERRORS SPACE WEATHER- “K” INDICES GEOID QUALITY POSITIONS TIED TO NSRS? BUBBLE ADJUSTMENT LATENCY, UPDATE RATE KNOWLEDGE OF ALL THE ABOVE = OPERATOR EXPERTISE
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16	SUNSPOT CYCLE Sunspots follow a regular 11 year cycle We are just past the low point of the current cycle Sunspots increase the radiation hitting the earth's upper atmosphere and produce an active and unstable ionosphere
17	IONOSPHERIC EFFECTS ON POSITIONING
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19	GNSS TO ANY DATUM GNSS ECEF X,Y,Z (WGS 84 & PZ90) NAD 83 (f,l,h) SPC N,E,h + GEOID XX = SPC N,E,H OR CALIBRATE TO 4-5 SITE POINTS IN THE DESIRED DATUM. THIS TECHNIQUE LOCKS TO PASSIVE MONUMENTATION IN THE PROJECT AREA.
20	WHY NETWORK RTK (RTN)?
21	WHY NETWORK RTK (RTN)? RTNs CAN BE SEAMLESSLY CONNECTED TO THE NSRS – This means: Regional Inter-GIS compatibility Continual accuracy and integrity monitoring Easy datum adjustment/change updates NO DISTANCE CORRELATED ERROR - Atmospheric, ephemeris corrections for the site of survey Data degrade gracefully outside of the network or if a reference station is down Overlapping RTN give the same results!
22	EXAMPLES OF RTN ADMINISTRATORS IN THE USA ACADEMIC/SCIENTIFIC SPATIAL REFERENCE CENTERS VARIOUS DOTS COUNTY CITY GEODETIC SURVEYS MANUFACTURER VENDOR NETWORKS AGRICULTURE MA & PA NETWORKS
23	"The NGS should provide real..." The NGS should provide real time RTCM data streams (via NTRIP) from a subset of the National CORS network- perhaps in a 200 Km spacing grid. These data streams will aid in the establishment, validation and monitoring of the RTNs by network administrators. NO CORRECTORS WILL BE BROADCAST. NGS encourages the institutions, who are providing real-time positioning services, to use the NGS-provided raw data in their operations so as to: (1) SUPPLEMENT the data from other GNSS base reference stations, and (2) use the positional coordinates and velocities of the GNSS stations contained in the NGS real-time network as FIDUCIAL VALUES for the positional coordinates and velocities of other real-time GNSS stations. The NGS could ASSESS AND ACCREDIT proposed or even current RTN reference station sites for obstructions, multipath, positional integrity - in short, for anything that might affect optimal performance of the RTN.
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27	THE ROLE OF THE NGS IN SUPPORT OF RTN TO BE AN RTN “RECOGNIZED” BY THE NGS: 4. Initial RTN reference station coordinates are produced by the individual RTN administrator. However, promulgated coordinates and velocities for the corresponding GNSS base reference stations will be compatible with the National Spatial Reference System at the level of 2-cm Horizontal and 4-cm (ellipsoid) height. Automated processes will enable RTN administrators to push daily data for all RTN reference stations to the NGS where a specific version of OPUS-DB will position the stations and archive the data. Three National CORS that are part of the RTN will be used as control stations for this OPUS-DB processing. TEQC may be utilized to QA/QC the data. Then, 60 day plots will be developed to graphically depict the deviation from predicted daily coordinates for each and every reference station.
28	THE ROLE OF THE NGS IN SUPPORT OF RTN Additionally, NOAA/NGS could stream satellite ephemerides, satellite clock parameters, iono and tropo models and even crustal motion models for public use. The NGS, continuing its role in support of accurate, reliable positioning, would study temporal macro variations in positions (seasonal, daily, ocean loading, atmospheric loading, subsidence, tectonic, etc.) and would study phenomena affecting accurate positioning (satellite orbits, refraction, multipath, antenna phase centers, geoid, etc.) The NGS will not stream data that is being streamed via NTRIP by another organization.
29	EXAMPLE OF WHY RTN REFERENCE STATIONS SHOULD BE MONITORED
30	THE ROLE OF THE NGS IN REAL TIME POSITIONING
31	EXPEDITING THE GUIDELINES THE NGS ENCOURAGES RTN USERS AND ADMINISTRATORS TO BECOME COOPERATIVE PARTNERS TO PROVIDE INPUT THAT WILL ENABLE VALUABLE DOCUMENTS TO BE DRAFTED THAT WILL BENEFIT THE PUBLIC WELFARE. - ESTABLISHING REFERENCE STATIONS - ADJUSTING NETWORKS - ACCURACY EXPECTATIONS VS. OBTAINED - BASELINE DISTANCES - ERROR MODELING - COMMUNICATION ISSUES
32	NGS SUPPORT OF RTN: SUMMARY NGS STREAMS UNCORRECTED RTCM DATA FROM THE BACKBONE CORS RTN NSRS COMPATIBILITY LEVEL- 2-cm H, 4-cm V RTN OVERLAP ACCURACY? ESTABLISHING REFERENCE STATIONS (COORDINATE INTEGRITY, SITE EVALUATION,) MODELS & TOOLS DATA ARCHIVING (OPUS-DB) DATA QA/QC
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34	NGS FTP LINK FOR PRESENTATION ftp://ftp.ngs.noaa.gov/dist/whenning/CORS FORUM/ CORS FORUM.ppt