SC – VRS Network

To Support Surveying and Machine Control

Presentation Overview

• Introduction• VRS Network Design• Antenna Mounting Designs• Server Network Design• Modeling• Network Testing• Network Integrity• Practical Applications

South Carolina Geodetic Survey

Marine Transportation

HighwayConstruction

Obstruction Charting

Utilities

SurveyingEngineering

Mapping

Infrastructure

Motivating Force for a Network Application

Antenna Hardware

Stainless Steel MountFor Masonry Buildings

Self Supporting 24 Foot Tower

Tamper-Proof Leveling Head

Server Network Design

Should IT Be a Shareholder?

5

6

7

Modeling

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I(λ,φ) = I0 +aλ∆λ + aφ∆φ 1 cm

-1 cm

2 – 12hr Multipath PlotsAreal Variant Ionospheric Model

The solution of Integer Ambiguityis influenced by external variables

Atmosphere - Tropo, IonClock Error - SV and ReceiverSV Orbit ErrorMultipathSeparation of Base and Rover

SC - VRS Network Design

VRS Is Not Built In a Day!There Are Many Stakeholders!!

They Are ALL Critical To Your Success

Test Network

11 Counties, 6700 Sq Mi, 10 VRS Base Stations, 50 Control Pts

VRS Absolute Accuracy

Comparison of VRS and NGS Height Mod ControlAbsolute Accuracy

Meters

Allowable 2-D RMSEr 95% = 1.7308 * RMSEr = (2.0*2.0 + 0.3*0.3 + 1.2*1.2)1/2 = 2.4 cm*

Allowable 1-D RMSEv 95% = 1.9600*RMSEv = (2.0*2.0 + 0.3*0.3 + 2.4*2.4)1/2 = 3.1 cm*

Time (sec) 300 60 5

Horizontal (cm) 1.98 2.40 2.41

Vertical (cm) 2.25 2.39 2.40

*(Local Accuracy2 + Eccentricty2 + System Design2)1/2

Station SCBY

Vertical Axis -0.010 to 0.014m

Poor Choice for a Base Station!

Vertical Axis -0.04 to 0.055m

Diurnal E-W Motion of a 90 Foot Spun Concrete Tower

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0Centimeters

Each Depicted Value Is A Mean Of Two 5-Minute Observations Spaced Approximately 21 or 27 Hours Apart

95% Less Than 2.5 CM From Published Value

Results From Test Of The SC RTN to Determine Accurate Ellipsoid Heights

Practical Applications

Tidal Datum Transfer

2 mile transfer0.05 ft uncertainty

VRS Elevation (ft) Leveling (ft) Difference4.557 4.560 0.0034.488 4.482 -0.0074.423 4.436 0.0134.656 4.649 -0.007

4.327 4.337 0.0104.528 4.528 0.0004.810 4.800 -0.0104.941 4.948 0.007

Mean/SDV 0.001/0.008

Classical Leveling vs VRS

1st Order Class 2 Leveling4 Surveyors4 days5.5km – 6mm

1 Surveyor4 hours12mm comparison

VRS Elevation (ft) Leveling (ft) Difference4.557 4.560 0.0034.488 4.482 -0.0074.423 4.436 0.0134.656 4.649 -0.007

4.314 4.265 -0.0494.327 4.337 0.0104.528 4.528 0.0004.810 4.800 -0.0104.941 4.948 0.0074.964 5.020 0.056

Mean/SDV 0.002/0.025

Comparison of VRS to Total StationRelative Accuracy

Grid Brg Angle Rt Grd Dist

TPT1 SURVEY 068/00/55TPT1 TPT2 207/30/58 220/29/57 544.669 VRS

220/29/55.2 544.678 Total Station139/30/03 Interior Angle

TPT2 TPT1 027/30/58TPT2 TPT3 198/49/59 188/40/59 957.778 VRS

188/40/57.2 957.769 Total Station171/19/01 Interior Angle

TPT3 TPT2 018/49/59TPT3 SURVEY 038/08/33 340/41/26 2165.470 VRS

340/41/27.5 2165.441 Total Station019/18/34 Interior Angle

SURVEY TPT1 248/00/55 837.523 VRS837.500 Total Station

SURVEY TPT3 218/08/33 029/52/22 Interior Angle029/52/21.0

360/00/00 VRS359/59/59.1 Total Station

Ellipsoid Height Distortions of 3CM or Greater

Network vs OPUS

-0.020 -0.016 -0.004-0.032 -0.021 -0.011-0.015 -0.012 -0.003-0.022 -0.020 -0.002-0.013 -0.015 0.002-0.020 -0.017 -0.003-0.024 -0.015 -0.009-0.041 -0.015 -0.026-0.007 -0.008 0.001-0.011 -0.012 0.001-0.018 -0.012 -0.006-0.021 -0.018 -0.003-0.003 -0.012 0.009-0.048 -0.020 -0.028-0.044 -0.019 -0.025-0.028 -0.018 -0.010-0.024 -0.026 0.002-0.026 -0.025 -0.001-0.027 -0.024 -0.003-0.037 -0.023 -0.014-0.035 -0.024 -0.011-0.017 -0.023 0.006-0.022 -0.021 -0.001-0.049 -0.026 -0.023

-0.025 -0.019 -0.007-0.012 0.005 0.010

2 – 10 Minute Sessions Separated by 27 Hours

MeanStd Dev

Pub-Obs Pub-Pred Obs-Pred

Predicted values are weighted* means of the Network-OPUS Differences

*Weight Equals Ratio of Base StationSeparation Multiplied by Assumed Error

Network Integrity

24-Hour Coordinate Spread 1 cm N & E1.5 cm Ellipsoid Ht

Semi-Major Axis ~ 1 cm

Concluding Remarks

• Number of Registered Users• Maintenance Plan• Replacement Plan• Integrity Monitoring• Cost• Subscription Fee• Questions?