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RTN Methodologies & Best Practices

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RTN Methodologies & Best Practices. Neil D. Weston National Geodetic Survey, NOS, NOAA. Silver Spring, MD July 31, 2013. RTN Basics. City limits. City limits. 100. Ref. Ref. 100. Ref. *. *. Northing (km). Northing (km). Ref. Ref. 0. 0. Easting (km). 0. Easting (km). 100. 0.

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slide1
RTN Methodologies & Best Practices

Neil D. Weston

National Geodetic Survey, NOS, NOAA

Silver Spring, MD July 31, 2013

slide2
RTN Basics

City limits

City limits

100

Ref.

Ref.

100

Ref.

*

*

Northing (km)

Northing (km)

Ref.

Ref.

0

0

Easting (km)

0

Easting (km)

100

0

100

Single baseline approach

Network approach

slide3
RTN Basics
  • Reference frame – adopt latest realization of NAD 83 (NAD 83 2011 epoch 2010.00)
  • CORS + RTN – include a few CORS in the RTN
  • Adjustments
    • Constrain CORS that are included
  • Base station monitoring
    • Process data periodically
    • Monitor coordinates over time
  • Base station information
    • Coordinates, velocities, epoch
slide4
RTN Basics and Formats
  • Receiver collection rate – minimum 1Hz
  • Data formats
    • Proprietary
    • Open standard
    • Compatibility
  • RTCM SC-104
    • Only true ‘open’ protocol
    • RTCM-2.1 Added RTK messages for dm levels at short distances
    • RTCM-2.2 Expanded for differential operations with GLONASS
slide5
RTCM Formats
    • RTCM-2.2, 2.3 RTK operations providing cm- level performance at short distances
    • RTCM-3.x More efficient; support RTK operations (GPS+GLONASS); network correction message
  • Common message types 2.x
    • Type 18, 20 – RTK uncorrected carrier phase data and carrier phase corrections
    • Type 19, 21 – RTK uncorrected pseudo-range measurements and appropriate range corrections
  • Common message types 3.x
    • 1004 – full observables
    • 1005 – reference station coordinates
    • 1007 – antenna description
slide8
Network RTK Processing Techniques & Applications
  • Virtual Reference Station – VRS
  • Area-Parameter Correction – FKP
  • Master-Auxiliary Concept – MAC
  • Grading, utilities, pipelines, roads
  • Landscaping, cadastral surveys, mapping
area correction parameters fkp
Area Correction Parameters - FKP
  • Network described using coefficients for a surface
  • Parallel surface with baselines less than 100 km
  • Reference station at the center of the “surface”
  • Software in rover receiver does the interpolation of corrections
  • Error information is provided for quality control and analysis
  • Single and bi-directional communications
virtual reference station vrs
Virtual Reference Station - VRS
  • VRS techniques is currently the most popular
  • Requires bi-directional communications
  • VRS observations constructed
  • Rover approx. position to NRTK center
  • Rover solution based on range between VRS and rover
  • VRS kept to preserve ambiguities
virtual reference station vrs1
Virtual Reference Station - VRS

Ref Sta.

NRTK

Center

Ref Sta. j

Rover

VRS Sta. i

Ref Sta.

master auxiliary concept mac
Master Auxiliary Concept - MAC
  • Rover position (NMEA) to processing center
  • Processing center chooses a master station – usually closest ref. station
  • Auxiliary stations are chosen from a 70 km catch circle
  • Rover receives MAC corrections via RTCM
  • Rover decides on method of interpolation of corrections and how the position is determined – double difference, for example
master auxiliary concept mac1
Master Auxiliary Concept - MAC

Aux k4

Auxiliary k1

Master j

Rover

70 km

Aux k2

Aux k3

slide14
RTK Processing

Network RTK Processes

Correction Generation

Correction Interpolation

Correction Transmission

Network Ambiguities

Network Corrections

Linear Interpolation

Surface Modeling

Grid-based Parameters

One way Comms.

Two way Comms.

FKP

VRS

State Space

Observation Space

Linear Combination

Least Squares Co-location

MAC

Net Adjust

slide15
Thank You

Neil D. Weston

Chief – Spatial Reference System Division

301-713-3191 x 103

[email protected]

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