FGCS

1
THE ROLE OF THE NGS IN REAL TIME POSITIONING
KENTUCKY ASSOCIATION OF PROFESSIONAL
SURVEYORS FEBRUARY 14, 2008
Bill Henning, PLS. NGS Geodesist William.Henning_at_n
oaa.gov
2
WORKSHOP OUTLINE

• Changes - Trends
• Real Time Positioning Background
• RTN basics
• RTN Problems Benefits
• The Role of the NGS in RTN
• Classical RT Positioning Guidelines Sneak-Peak
• Discussion/ Questions

• Ngs ftp site DOWNLOAD ftp//ftp.ngs.noaa.gov/dist
  /whenning/KAPS2008
• /KAPS2008.ppt

3
The universe is change our life is what our
thoughts make it.Marcus Aurelius Antoninus,
MeditationsRoman Emperor, A.D. 161-180 (121 AD -
180 AD)The more you learn, the more you
realize you dont know Anonymous
4
RT ACRONYMS US
R
MAC
NAD 83
GRS 80
WGS 84
NAVD 88
VRS
ITRF 2000
NGVD 29
FKP
GEOID 06
5
CHANGE.
1955
2007
6
CHANGE.
7
Grade stakes are becoming a rarity on large
sites.
Machine Control
Slide by Jim Waters, TNDOT
Graphics Courtesy of Caterpiller Inc.
8
CHANGE.
MAPPING.
9
Height Modernization
OLD FIRMS SCALED HORIZONTAL
LIDAR and Derivative Products CONTROLLED FROM
RTN (Light Detection and Ranging )
OLD REMOTE SENSING
Slide by Gary Thompson, NC Geodetic Survey
10
2000/-
CHANGE.
2007
1977
11
CHANGE.
GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS)

• 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

12
STANDALONE POSITIONING BY 2017?
CHANGE.
10-15 cm???
BETTER RESISTANCE TO INTERFERENCE FASTER
AMBIGUITY RESOLUTION

• C/A Code on L1
• C/A Code on L2
• New Code on L5

13
FAIRFAX COUNTY, VIRGINIA
CHANGE.
GEODETIC CONTROL PHOTOGRAMMETRIC PROJECTS
MANAGED IN GIS SOFTWARE
14
(No Transcript)
15
GNSS DERIVED HEIGHTS
CHANGE.

• 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 gt 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)

PASSIVE
ACTIVE
16
BRINGING IN SITE CONTROL

• CLASSICAL TRAVERSE ½ - 1 DAY COMPS
• CORS 2- 5 ½ HOUR SESSIONS
• CLASSIC OPUS 2 HOURS REDUNDANCY
• OPUS RS 20 MINUTES
• CLASSICAL RT 3 MINUTES REDUNDANCY
• NETWORK 2 MINUTES REDUNDANCYTHE TREND IS
  TO PROVIDE COORDINATES IN THE MINIMUM TIME

17
Subsidence Areas
Questionable Elevation Data
18
EXTREME SUBSIDENCE
19
NGS Bench Marks
20
Monumented Points Deterioration
Disturbed Geodetic Control Coordinates/Elevations
Questionable
Destroyed Geodetic Control No Coordinates/Elevatio
n
21
Maintaining the Passive Monumentation
Infrastructure is a Challenge!
10,461 benchmarks remain in NGS database
20 reported not found or in poor condition
23 in last 25 years were reported as good
Only 12 reported as good in last 10 years
22
CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS)

• Installed and Operated by various
  Federal-State-local Agencies (190) Total 9/2007
  1025 National, 166 COOP
• NOAA/National Geodetic Survey
• NOAA/OAR Forecast Systems Lab
• U.S. Coast Guard - DGPS/NDGPS
• Corps of Engineers - DGPS
• FAA - WAAS/LAAS (Future)
• State DOTs
• County and City
• Academia
• Private Companies

CHL1 - CAPE HENLOPEN, DE
23
2007 National Readjustment of 70,000 GPS Points
CHANGE.
NAD 83/86 NAD 83/HARN(1991) NAD 83
HARN REOBS(1999) NAD 83 CORS 96
(2002) NAD 83 (NSRS2007)
24
Web Statistics
25
Online Positioning User Service (OPUS)

• Users submit GPS data to NGS, where they are
  processed using NGS computers and software.
• The resulting precise positions are e-mailed
  back to the user.
• Featured as the DOC E-Gov Success Story for FY06
• Over 450,000 solutions processed since beginning
  operation 4 years ago
• OPUS-Rapid Static was brought online in
  February, 2007. This new tool allows users to
  submit as little as 15 minutes of data (versus 2
  4 hours with standard OPUS).

26
REAL TIME POSITIONING

• IT DEPENDS

CLASSICAL RTNETWORK RT (RTN)
27
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

28
Some Other Concepts to Know.
Carrier Phase Code Phase VHF/UHF Radio
Communication CDMA/SIM/Cellular TCP/IP
Communication Part Per Million Error (PPM) WGS 84
versus NAD 83 GPS and GLONASS Constellations
Accuracy versus Precision Multipath Root Mean
Square (RMS) CalibrationsLatencySignal to Noise
Ratio (S/N or C/N0)Float and Fixed
Solutions Elevation Mask
29
COORDINATE SYSTEMS

• Latitude Longitude
• State Plane Coordinates
• UTM Coordinates
• NAD 83
• NAD 27
• NAVD 88
• NGVD 29
• WGS 84
• ITRF
• .. Having trouble deciding what to use?

30
THE ELLIPSOIDA MATHEMATICAL MODEL OF THE EARTH
N
b
a
a Semi major axis b Semi minor axis f
a-b Flattening a
S
31
GEODETIC DATUM
32
GPS - Derived Ellipsoid Heights
DATUM SOSO SURFACE ORIGIN SCALE ORIENTATION
GRAVITY
Z Axis
(X,Y,Z) P (?,?,h)
P
h
Earths
Surface
Zero
Meridian
Reference Ellipsoid
Y Axis
?
?
Mean Equatorial Plane
X Axis
33
ITRF SYSTEM
GPS DORIS VLBI SLR/LLR
34
ITRF VELOCITIES
35
SIMPLIFIED CONCEPT OF ITRF 00 VS. NAD 83
h83
h00
Earths
Surface
ITRF 00
Origin
2.2 meters
NAD 83
Identically shaped ellipsoids (GRS-80) a
6,378,137 meters (semi-major axis) 1/f
298.25722210088 (flattening)
Origin
36
TYLER CORS (TEXAS DOT)COORDINATES
37
NAD 83 CORS 96 EPOCH 2002
WHEN WAS IT ADJUSTED?
WHAT SNAPSHOT IN TIME DO WE WANT TO SEE?
DATUM
ITRF 00 EPOCH 1997, EPOCH 007/04/15
38
PLANNING
GPS PDOP
GPS GLONASS PDOP
39
PLANNING
GPS
GPS GLONASS
40
DOP
41
300 KM
80 KM
42
TROPOSPHERE DELAY

• The more air molecules, the slower the signal
  (dry delay)
• High pressure, Low temperature
• 90 of total delay
• relatively constant and EASY TO CORRECT FOR
• The more water vapor in the atmosphere the slower
  the signal (wet delay)
• High humidity
• 10 of total delay
• Highly variable and HARD TO CORRECT FOR

Ionosphere
troposphere
10 KM
GREATER THAN 10 KM
43
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

http//www.sec.noaa.gov/
44
IONOSPHERIC EFFECTS ON POSITIONING
AVERAGE IONO- NO NETWORK
HIGH IONO- NO NETWORK
2D PRECISION/ACCURACY (CM)
SINGLE BASE RTK _at_ 10 KM
(2000-2002)
(1994-1995)
NETWORK SOLUTION _at_ 30 KM
WITH NETWORK
DISTANCE TO REFERENCE STATION (KM)
(SOURCE-BKG- GERMANY)
45
RTK PPM ERROR VS. BASELINE LENGTH
3-D error _at_ 95 Confidence
46
DONT DO IT!
BE AWARE OF MULTIPATH ENVIRONMENTS
47
(No Transcript)
48
BEACH/VEGETATION SURVEY
LOSS OF LOCK DUE TO CORNFERENCE
49
(No Transcript)
50
TO GET TO THE BOTTOM LINE..
51
(No Transcript)
52
CHALK POINT RTK
BASE
ROVER
53
CHALK POINT RTK
54
CHALK POINT RTK
55
Two Days/Same Time
-10.254 -10.251
gt -10.253
THE IMPORTANCE OF REDUNDANCY
Difference 0.3 cm
Truth -10.276
Difference 2.3 cm
Two Days/ Different Times
-10.254
gt -10.275
-10.295
Difference 4.1 cm
Truth -10.276
Difference 0.1 cm
56
GNSS TO ANY DATUM

• GNSS ECEF X,Y,Z (WGS 84 PZ90)
• NAD 83 (?,?,h) SPC N,E,h
• GEOID XX SPC N,E,H
• OR
• CALIBRATE TO 4-5 SITE POINTS IN THE DESIRED
  DATUM. THIS CAN ALSO BE USED TO LOCK TO PASSIVE
  MONUMENTATION IN THE PROJECT AREA.

57
ELLIPSOID, GEOID ORTHO HEIGHTS
58
EXPECTED NSRS ORTHOMETRIC HEIGHT ACCURACIES

• DGPS 1-2 METERS, CODE PHASE
• SINGLE BASE RTK 2-5 CM, AVERAGE OF REDUNDANT
  POSITIONS 10 KM
• RTN 2-6 CM, WITHIN NETWORK
• CORS/OPUS 2-5 CM, 4-HOURS OF DATA
• STATIC GPS 2 CM LOCALLY USING GUIDELINES
• GEODETIC LEVELING 1 CM IN 10 KM (3RD ORDER)

59
INITIAL AUTONOMOUS POSITIONS OK!
60

• L1 RTKHolds great interest because of its
  potential to reshape the survey/mapping
  marketplace. It will fill a gap between L1 static
  systems and high-end L1/L2 RTK systems.
• L1 RTK systems will be half the price of L1/L2
  systems maybe even one third.
• Baseline lengths will be limited to a few
  kilometers
• Initialization times will be measured in terms
  of minutes rather than seconds
• Accuracy will be the just as good as high-end
  L1/L2 RTK systems.
• Needs a good Satellite constellation.
• Information Courtesy of Eric Gakstatter, GPS
  world. December 2006

61
TYPICAL RTK POSITIONING APPLICATIONS

• Site Control redundant check, 180 epochs,
  GOOD CONDITIONS
• Boundary locations same as above
• Topo as quick as you can enter the attributes
• Aerial targets 30 epochs with good conditions,
  recommend redundant check especially for
  vertical
• Point recovery as quick as you can walk
• Construction or Design Stake out 10 epochs or
  as fast as you can plumb the rod. Recommended use
  for main points rather than every intermediate
  station.

62
(No Transcript)
63
CLASSICAL RT POSITIONING
FROM GUIDELINES BEING INTERNALLY VETTED NOVEMBER
2007
64
RTK POSITIONING

• The rover tries to resolve the INITIAL number of
  phase cycles from each satellite and keeps
  updating the count by derivatives of various
  error sources with respect to time. (must
  maintain lock on the satellite or re-initialize).
• Conditions that are modeled in the carrier phase
  cycle observable equation are topocentric range
  (receiver to satellite), receiver clock error,
  satellite clock error, ionospheric advance,
  tropospheric delay, receiver hardware delay,
  satellite hardware delay, multipath (in cycles)
  and measurement noise.

65
WARNING!BORING TECHNICAL STUFF AHEAD- NEXT 10
SLIDES
66
THE INTEGER AMBIGUITY
Resolving the integer ambiguity allows phase
measurements to be related to distances
Dl First Partial Wavelength
Nl Integer Ambiguity
Distance Nl Dl
67
RTN DATA FLOW
Wide laning, narrow laning Kalman filtering,
recursive or dynamic least squares
Linear combination of the frequencies to
eliminate iono error for long baselines gt 30 km
68
SOME REAL TIME INTEGER FIXING TECHNIQUES

• Wide Laning (L1 L2 c (speed of light)
  (1575.42 MHz 1227.60 MHz) or 299,792.458
  Km/sec 347.82 MHz 0.862 m wave length.
• Narrow Laning(L1 L2 c (speed of light)
  (1575.42 MHz 1227.60 MHz) or 299,792.458
  Km/sec 2803.02 MHz 0.107 m wave length
• Iono Free f(L1)ion-free a1.f(L1) a2.f(L2)
• with a1 f12(f12 - f22 ) and a2 - f1 . f2 (f12
  - f22 )
• Triple Differencing
• Kalman Filtering
• Double Differencing

69
CARRIER PHASE PROCESSING FLOW
REFERENCE
Parameterization of DGPS Carrier Phase Errors
Over a Regional Network of Reference
Stations (URL http//www.geomatics.ucalgary.ca/G
radTheses.html) by Georgia Fotopoulos August 2000
70
UNDIFFERENCED PHASE OBSERVABLE (CYCLES)
L1 5.255 CYCLES PER METER
71
SINGLE DIFFERENCE

• TWO RECEIVERS, ONE SATELLITE, SAME EPOCH.
  ELIMINATES SATELLITE CLOCK ERROR
• (TWO SATELLITES, ONE RECEIVER ELIMINATES RECEIVER
  CLOCK ERROR)

72
SINGLE DIFFERENCE
73
DOUBLE DIFFERENCE

• DOUBLE DIFFERENCING TWO RECEIVERS, TWO
  SATELLITES, SAME EPOCH. ELIMINATES RECEIVER CLOCK
  ERROR, REDUCES OTHER ERRORS

74
DOUBLE DIFFERENCE
difference between two single differences of
two receivers and TWO satellites at the same epoch
75
TRIPLE DIFFERENCE

• If the receiver retains lock between epochs, the
  double difference ambiguity remains the same for
  each epoch and therefore will cancel out in the
  triple difference equation. If the receiver loses
  lock, the triple difference solution that
  contains that loss of lock will show as an
  outlier and therefore will show the cycle slip
  during processing.

76
TRIPLE DIFFERENCE
Cancels Double Difference integer cycles
77
RESULTING DIFFERENCED PHASE OBSERVABLE (CYCLES)
ASSUMED THE SAME FOR ROVER BASE IN SINGLE BASE
RTK
LEAVES MULTIPATH, MEASUREMENT NOISE RANGE TO
SATELLITE
78
WHY NETWORK RTK (RTN)?
Because the requirement for a user base station
is removed

• No reconnaissance/recovery of passive control
• No time lost setting up and breaking down a base
  static
• No base baby sitting, therefore labor cost is
  reduced No base means with two rovers the
  project is completed in half the time
• savings

79
WHY NETWORK RTK (RTN)?

• 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

NSRS
80
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
• In other words - Everything fits together

NSRS
81
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

82
RTN- THE GOLDRUSH

• Easy, quick, hands-off, accurate, homogenous,
  repeatable, cost efficient, labor saving- these
  are all terms that describe the RTK network and
  which bring large numbers of geospatial
  professionals in the public, private and academic
  sectors great benefit.

83
RTK vs. RTN
RTN
RTK
84
RTN FLAVORS

• Virtual Reference Station (VRS)
• Flachen Korrektur Parameter (FKP)
• Master-Auxiliary Concept (MAC)
• All In-Receiver
• Closest Network Base

85
VRS
86
VRS- SUMMARY

• Rover sends NMEA 0183 format message to RTN
  server with raw position.
• RTN server, using interpolated phase
  corrections, computes a position at this point,
  which then becomes a VRS.
• Rover computes a base line from this VRS to get
  its position, similar to traditional single base
  RTK.

87
VRS

• Requires two-way communication
• Compatible with legacy equipment
• RTCM v 2.3 format style messages OK
• single baseline from the VRS
• Nothing needs to be modified in the rover
• Rover can not optimize corrections
• Virtual Monument

88
FKP
89
FKP

• Simplifies VRS approach by producing a set of
  coefficients for the corrections (to each
  satellite and each station) for areas near to
  each reference station rather than building a
  VRS.
• Possible risk of inconsistent tropospheric
  modeling because broadcast of reference station
  data is modified to correct for atmospheric and
  orbital errors but may be modeled differently in
  rover.

90
FKP- SUMMARY

• Broadcast set of modeling coefficients for each
  satellite to cover a specific area.
• Rover generates own corrections using
  ionosphere, troposphere, orbit coefficients.
• Uses proprietary RTCM Type 59 message.
• Not compliant with RTCM because reference
  station data is broadcast with modified data to
  correct for atmospheric and orbital error.

91
MAC
92
MAC

• One Master station identified to broadcast
  standard observables along with the difference in
  corrections for each satellite at each auxiliary
  station and the difference of their coordinates.
• rover interpolates corrections and applies to
  its observables.
• Results in a single baseline from master station
  using rover processed corrections.

93
MAC

• Capability for sophisticated error modeling
  techniques at the rover or to just apply simple
  interpolation of network corrections.
• Full observables are transmitted from the master
  station enabling a single baseline solution if
  rover can not interpret the network messages.
• Built on the RTCM v 3.x protocol

94
ALL IN ROVER

• No control center or master station
• All observables from all reference stations are
  sent to rover
• Rover does all modeling of corrections and
  processes baseline
• Major horsepower is needed at the rover, but
  eliminates the possibility of errors from
  differing modeling methods by different hardware.

95
SOME INTERPOLATION METHODS

• Distance based linear interpolation
  method
• Linear interpolation method
• Low order surface model
• Linear combination method
• Least squares collocation method
• None! (in-the-rover solution)

96
CLOSEST STATION

• Rover uses broadcast from closest reference
  station
• Single baseline, no network modeled corrections
• Typically a Ma Pa network of antennas on the
  roofs
• Back to accounting for 1 PPM error

97
EASY DRIVE NETWORK-TEXASCLOSEST BASE
Select the nearest base station to your position
or any network base station to upload data for
corrections. The RTK network allows Leica GPS
user to move from job to job with only a rover. 
REFERENCE STATIONS ARE ESTABLISHED IN STRICT
CONFORMANCE TO NGS STANDARDS. Users can observe
direct measurement from multiple, tangible
reference stations, while simultaneously
collecting real time data in multiple geodetic
formats.  Purchase a Leica base station from Easy
Drive and receive immediate access to the RTK
network.
98
RTCM SC104- V. 3.X

• Adds message types for RTN
• Designed for Glonass, Galileo, L2c, L5
• 50 less bandwidth than v 2.3, but more message
  types
• Simplifies network software tasks (only must
  resolve ambiguities).
• Standardizes RTN information and models
• Message types 1001 1013 support traditional
  GNSS single base and differential applications
• Message types 1014-1020 for RTN messages.
• Message types 4001-4096 reserved for proprietary
  use, one message to a company

99
POSITIONING FLOW
100
RTCM v. 3.X
101
RTCM V.3.1
102
RTCM V 3.1

• MASTER BROADCASTS OBSERVABLES AND CORRECTION
  DIFFERENCES FOR AUXILIARIES
• ROVER COMPUTES CORRECTION
• NO DUPLEX COMMUNICATION NECESSARY
• REFERENCED TO A REAL MONUMENT
• NO MODELING ERRORS FROM DIFFERENT ALGORITHMS
  (LIKE POSSIBLE WITH FKP)

103
RTCM SC104- V. 3.X

• Adds message types for RTNs
• Designed for Glonass, Galileo, L2c, L5
• 50 less bandwidth than v 2.3, but more message
  types
• Simplifies network software tasks (only must
  resolve ambiguities)
• Standardizes RTN information and models

104
RTCM v. 3.0

• Message types 1001 1013 support traditional
  GNSS single base and differential applications
• Message types 1014-1020 for RTN messages.
• Message types 4001-4096 reserved for proprietary
  use, one message to a company

105
RTN EXAMPLES

• ACADEMIC/SCIENTIFIC
• SPATIAL REFERENCE CENTERS
• VARIOUS DOTS
• COUNTY
• CITY
• GEODETIC SURVEYS
• MANUFACTURER
• VENDOR NETWORKS
• AGRICULTURE
• MA PA NETWORKS

106
(No Transcript)
107
RTN OVERLAP DOT PRIVATE SECTOR
108
RTN OVERLAP VRS DOT MAC DOT
109
MESA COUNTY RTRN
NGS SANCTIONED!
DISCLAIMER AND LIMITATION OF LIABILITY MESA
COUNTY, COLORADO, shall in no event be liable for
any lost profits, and special, indirect or
consequential damages to any party, arising out
of or in connection with the use or the inability
to use the data hereon or the services provided.
Mesa County provides this data and it's services
as a convenience to it's customers. Furthermore,
Mesa County reserves the right to change, revise,
or otherwise discontinue published data and/or
these services at any time without further
notice.
110
CRTN
REVERSE PROCESSING AVAILABLE RTK RECEIVER NOT
NECESSARY PDA FRIENDLY
111
Real Time for Agriculture
DUAL FREQUENCY CARRIER RTK NOT CODE
112
The cities of Seattle, Renton, Bellingham, Kent,
Auburn, and Shoreline The counties of King,
Snohomish, Skagit, Island, Jefferson, Thurston,
and Pierce Kitsap Public Utility District, the
Washington State Department of Transportation and
the Spatial Reference Center of Washington
(SRCW) academic and scientific institutions and
projects like the Pacific Northwest Geodetic
Array (PANGA), Central Washington University, the
University of Washington, and Renton Technical
College.
www.wsrn.org
113
TRIMBLE MANUFACTURER
114
PASSIVE AND ACTIVE MONUMENTS
115
PASSIVE AND ACTIVE MONUMENTS
116
PASSIVE/ACTIVE MONUMENTATION

• The realization of a datum in passive
  monumentation is on points that are moving
• The realization of a datum in active
  monumentation is on stations that are moving
• The positions of the active monumentation in
  relation to a datum can be monitored every day
• The positions of the passive monumentation in
  relation to a datum are never routinely monitored
  
• The relationship between passive monuments and
  active monuments changes with time
• The relationship between any one passive monument
  and active monuments may change differently than
  that of other passive monuments to the active
  monuments
• Passive monument movement is apt to be more
  noticeable the larger the area of interest.
• Some passive monuments move faster than others
• Some active monuments move faster than others
• How long should one continue to use the published
  NAD 83 coordinates of a passive monument or
  active monument?
• Should one apply velocities to passive monuments
  routinely?
• How long can a real-time network (RTN) keep
  adjusted coordinate values on its reference
  stations without performing a readjustment
  reflecting the changed positions?
• Should RTN coordinates always be obtained and
  maintained from ITRF adjusted positions and
  transformed to the users datum (NAD 83)?
• When can an RTN provide adequate survey grade
  elevations without calibrating to bench marks?
• What is the best strategy to deal with the
  possible positional error in CORS that are used
  to develop RTN coordinates?

117
A CASE STUDY IN ADOPTING REFERENCE STATION
COORDINATES
118
8-STATION NETWORK ADJUSTMENT
24 DAYS OF DATA PRECISE ORBITS APRIL 2007 NGS
VELOCITIES (HTDP) IN ITRF
119
MINIMALLY CONSTRAINED CORS ADJUSTMENT
1
CORS FIT 1-3 MM HORIZONTAL 8-25 MM VERTICAL
120
HOLDING ALL 4 CORS TO MASTER
INTRODUCES NETWORK TRANSFORMATION PARAMETERS
(DEFLECTIONS)
2
121
TRANSFORMATION PARAMETERS
122
HOLDING MASTER FROM PREVIOUS
3
NO ROTATION TO CORS
123
AL 4 CORS 8 STATIONS CORS TO MASTER ONLY
INTRODUCES NETWORK TRANSFORMATION PARAMETERS
(ROTATIONS/DEFLECTIONS) MASTER IS SAME AS
3 OTHERS CHANGE (HORIZ. OK, VERT.VARIES)
4
124
TRADITIONAL ADJUSTMENT
RESULTS SIMILAR TO PREVIOUS- MAINLY VERTICAL
ERROR INCONSISTENT ACROSS THE NETWORK
5
125
RESULTS
126
CONCLUSIONS

• USE CORS TO TIE TO NSRS (BEST FIT)
• USE ONE MASTER STATION IN RTN
• CONSTRAIN RTN TO MASTER
• INTERNAL PRECISION AND CONSISTENCY THEN ALLOWS
  ERRORS TO BE PLACED IN MORE REALISTIC AREAS
• ALLOWS VERTICAL COMPONENT ERROR OF THE CORS TO BE
  MITIGATED
• THE ROVER POSITION SHOULD BE CONSISTENT IN
  RELATION TO ANY RTN REFERENCE STATION
• Dr. Richard Snay Adjust RTN stations to all
  surrounding CORS with weighted values

127
LOUISIANA SRC- GULFNET
128
LEICA GEOSPATIAL- ATLANTA
GEORGIA REFERENCE NETWORK
129
E-GPS (TRIMBLE)-GEORGIA
OVERLAP WITH LEICA
130
ALLEN-PRECISION ATLANTA (TOPCON)
OVERLAP WITH TRIMBLE LEICA DO ALL THREE GIVE
THE SAME COORDINATES FOR THE SAME POINT?
131
NORTH CAROLINA GEODETIC SURVEY
132
SOUTH CAROLINA GEODETIC SURVEY
133
Test Network
SOUTH CAROLINA GEODETIC SURVEY
11 Counties, 6700 Sq Mi, 10 VRS Base Stations, 50
Control Pts
134
VRS Accuracy
Comparison of VRS and NGS Height Mod Control
Meters
Allowable 2-D RMSEr 95 1.7308 RMSEr
(2.02.0 0.30.3 1.21.2)1/2 2.4 cm
Allowable 1-D RMSEv 95 1.9600RMSEv
(2.02.0 0.30.3 2.42.4)1/2 3.1 cm
WHY DO YOU SUPPOSE THE VERTICALS ARE SO GOOD?
(Local Accuracy2 Eccentricty2 System
Design2)1/2
135
LOYOLA SPATIAL SYSTEMS- RTKNET
136
KEYSTONE - KEYNET
137
CARON EAST -
138
EVALUATE THE BUSINESS MODEL OF THE AVAILABLE RTN
PROVIDERS

• REFERENCE STATION COST?
• SUBSCRIPTION COST?
• RTK GEAR THAT CAN BE USED?
• COST/BENEFIT RATIO

139
ISSUES WITH RTN POSITIONING

• Passive Monument MovementSubsidence, Disturbed?
• Subscription Cost?
• Set Up Cost?
• How When is RTN adjusted?OPUS, Published,
  Local
• Datum, Epoch?Passive HARN vs. CORS 96(2002),
  etc.
• Communication Gaps?Local Area Service provider
• Accuracy?Residual Errors
• Formats CMR, CMR, Proprietary,RTCM 3.1?, 2.3?
• RTK gear that can be used?

140
THE ROLE OF THE NGS IN SUPPORT OF RTN

• The NGS should provide real time RAW 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.
• 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.

141
NGS HEADQUARTERS
HNPT
MDSI
NGS TESTING SITES CORS STATIONS HNPT MDSI
142
WELCOME LINKS PAGE
143
REGISTRATION PAGE
144
THE ROLE OF THE NGS IN SUPPORT OF RTN
TO BE AN RTN RECOGNIZED BY THE NGS

• 1. Real-time networks meet prescribed criteria in
  terms of site stability and data quality. (NGS
  National Cooperative CORS site guidelines by
  Giovanni Sella) http//www.ngs.noaa.gov/CORS/Coop/
  the_details.html
• 2. 10 or 3 (whichever is greater) of any RTN are
  National CORS and are well distributed.
• 3. Different brands of user equipment can operate
  with the real-time services from the different
  networks to the greatest extent possible.

145
REFERENCE STATION EXAMPLE LEICA, PRINCE
FREDERICK, MD.
http//www.ngs.noaa.gov/CORS/Coop/the_details.html
146
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 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 processing. QA/QC of data will be
  done. Then, 60 day plots will be developed to
  graphically depict the deviation from predicted
  daily coordinates for each and every reference
  station.

147
SOME FLAVOR OF OPUS FOR ARCHIVING
control station description
control stationphoto
GPS data (4hours)
observationnotes
optional for existing stations.
QA/QC2 reviews
OPUS websitehttp//geodesy.noaa.gov/OPUS for
registered users
control station monument
public datasheet
148
REGISTER THE RTN REFERENCE STATIONS

• Registration stores the following
• Name
• Address
• Agency
• Experience- GPS OPUS

OPUS websitehttp//geodesy.noaa.gov/OPUS for
registered users
149
(No Transcript)
150
EXAMPLE OF WHY RTN REFERENCE STATIONS SHOULD BE
MONITORED
SUBSIDENCE
6 MM / YEAR
ENGLISH TURN CORS
151
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.

152
THE ROLE OF THE NGS IN REAL TIME POSITIONING
DYNAMIC DOCUMENTS
1. NGS User Guidelines for Single Base GNSS
Real Time Positioning FY 2007 (Draft
Completed!) 2. NGS Guidelines for GNSS Real
Time Positioning in RTN FY 2008-9 a.
Design b. Construction c. Administetion d.
Users
153
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

154
NGS SUPPORT OF RTNSUMMARY

• 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)
• DATA QA/QC

155
1807
2007
William.henning_at_noaa.gov
156
NGS FTP SITEftp//ftp.ngs.noaa.gov/dist/whennin
g/KAPS2008