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NYSDOT CORS
Past, Present and
Future
Ron Frederiks
[email protected]
Lots of Acronyms!!!!!!
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GPS – Global Positioning System
ABGPS – Airborne Global Positioning System
CORS – Continuously Operating Reference
Stations
NGS – National Geodetic Survey
GIS – Geographic Information System
RTK – Real Time Kinematic Positioning versus
Post Processed Positioning
What is GPS?
Global Positioning System
 Satellite-based timing and position
 24 satellites (very high orbit)
 Developed by U.S. Department of Defense
 Considered a Public “Utility”
 Signals available free of charge
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Satellite Ranging
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Measuring the distance from a satellite
Measuring the travel time of radio signals
Signal travels at the speed of light
Trilateration
Ideally, the three spheres will intersect at a discrete
point.
3 seconds out
5 seconds out
7 seconds out
Accuracy of GPS
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Depends on several variables
 Time
spent on measurements
 Design of receiver
 Relative positions of satellites
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Can be more than 20 meters – autonomous
Sub meter to 5 meters with differential GPS
Sub centimeter with survey products and
differential GPS
Differential Correction
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What is it?
 Differential
Correction is the process of correcting
GPS data collected by a user, with data recorded
simultaneously at a base station, in order to improve
accuracy.
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CORS stations serve as the base stations for
differential correction
 Best
results achieved when distance is minimized
between users receiver and the base station.
 Dense network of reference stations is desirable.
Differential GPS
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Two receivers track the SAME signals and,
therefore, errors at the SAME time
User
Base
Base Stations
Before NYSDOT CORS, we had to rely on
the NGS CORS network
 Many gaps in the NGS CORS network
 NGS CORS stations collect data at
different rates
 NGS CORS stations were not always
reliable
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NGS CORS Network
Data Availability (OSPA)
Data Availability (SYCN)
NYSDOT CORS
Conceptualized requirements in 2004
 Contract let in Spring 2005
 Installation Fall of 2005 thru February 2006
 Publishing Static Data to NGS: March 2006
 Publishing RTK Corrections Summer/Fall
2006
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What is the NYSDOT CORS?
 Initially, a Network of 36
Stations Across NYS
 Intended Benefits of CORS
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Primary Benefit is Publication of Static GPS
Data for Positioning of Project Control
 Secondary Benefit is Publication of RTK
Corrections (for Terrain Data Positioning and
Construction Equipment Guidance)
NYSDOT CORS
CORS on 3/30/2006
Data Availability
CORS Station Installations
 GPS Receivers Installed on Secure DOT Buildings
 Each Antenna Mounted on an 3” Aluminum Mast
 Most Masts are Attached to Masonry Load Bearing
Walls
 Connected to DOT Statewide (WAN) Network
 GPS Data Collection is Totally Automated
 Collects & Transmits Data 24/7/365
 Automated Network Processing at MO DOT in Albany
 Automated Data Backup – In Case of Network Outage
 NYSDOT CORS System Will Include Leica Hardware
& Software
CORS Installation
CORS Hardware
Central Statewide Data Management
 Network Monitored & Managed by DOT Network
Administrators
 Stations Can be Controlled Remotely from Albany
(Set collection rates – view satellites)
 Alarm System is Included to Warn of Data Flow
Interruptions
 24 Hour Turnaround on Hardware Repairs
 UPS Backup Power Source at all Stations
 Continuous Monitoring of CORS Network Integrity
to Detect Movement
 NGS and Leica also Monitor CORS Network
Integrity
NYDOT CORS
IT Infrastructure
Control Sites/
Log Static Data
Distribute Static Data
Produce Real Time
Data Streams with
Corrections
18 Stations
Distribute Real Time
Data Streams
Distributes Static
Data
RTK Proxy Server
RTK Data distribuiton
18 Stations
Real Time Network Processing
Log .5 sec.
Static data
½ hourly files
Stream 1 sec.
Raw Data for RTK
net processing
Distribute:
•1 sec hourly static RINEX Files to
RTK Proxy Server
•1 sec hourly static RINEX for
internal archive.
•.5 second ½ hourly raw data files
to NGS
•.5 second 12 hour RINEX files to
NYSDOT Photogrammetry
Distribute:
•1 sec hourly RINEX
Static Data
•Single Baseline RTCM
•Nearest Site RTCM
•Single Cell Network
RTCM
•Automatic Cell Network
RTCM
Servers
Site server 24
Network server 25
Site server 45
Publication of Static GPS Data
 Automated Publishing of Static Data Files to
National Geodetic Survey (NGS)
 Static Data Files will be Available to Public from
NGS – via CORS Website
 Static Data will be Published by NGS in RINEX
Format
 RINEX Format can be Used by Most GPS
Processing Software
 NGS Adjusts National Network, Publishes Positions
for Reference Stations, and Distributes Station
Data For the National Spatial Reference Network
 Possibly (in the Future) Incorporate 5 New CORS
Stations Being Installed by NY City
Envisioned Web Delivery
NGS
Spider Web
Publication of Real Time
Kinematic (RTK) Corrections
 Automated Publishing of RTK Correction via Internet IP
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Address
RTK Corrections can Either be Solved by a Single
Baseline from a CORS Station, or by a Modeled
Network Solution From a Group of CORS Stations
RTK Corrections will be Streamed Out Thru an IP
Address on the Web (User determined data format)
User Accounts Will be Necessary to Access RTK
Corrections
DOT Will Not Charge $ For User Accounts or for Data
Data Can be Accessed by Wireless Phone with Internet
Data Service Plan from a Wireless Provider
Unlimited Number of Users Can Access Data
RTK Clusters
RTK Saratoga test of Cell
Verizon Coverage
Future of NYSDOT Cors
NYSDOT CORS Mission
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Ensure Accuracy By:
 Network Positions Monitored by NGS & by DOT CORS Software
 Station Positions Processed Against National Spatial Reference
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Network
Station Positions Reliant on Continuous Network Monitoring, not Single
Station Coordinate
Ensure Reliability By:
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Data Interruptions or Station Movements Linked to DOT Alarm System
24 Hr Contracted Maintenance and Hardware Repair
Data Backups Eliminates Data Loss if System Should Go Down
Single Point of Contact and Control of Data Collection Settings
Provide Ease-Of-Use By:
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Standardized Non-Proprietary Data Formats
Universally Usable With Most Major Manufacturers
Easily Accessible RTK Data Via Internet
No User Cost Charges for Data
RTK Usable Anywhere Wireless Access is Available
Sample ABGPS CORS Project
Block of photographs near Watertown
 ABGPS data used for QA/QC of the aerial
photos
 ABGPS data used in Aerotriangulation
adjustment to reduce the amount of
ground control
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ABGPS Antenna
Obtaining XYZ Coordinates
ABGPS data post-processed using a base
station near the project area
 Used NYSDOT CORS station in
Watertown (NYWT)
 Processed with GrafNav software
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 Specifically
designed for differential correction
of ABGPS data
Plotted in GIS
Fall 2005 Flights in GIS
In Conclusion
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NYSDOT Currently has 36 CORS stations
NYSDOT is planning to expand
NYSDOT working with NGS to make NY CORS
part of the National CORS
Data will be made available at no cost
Data will be delivered through web (non RTK)
and registered users (RTK only)
Data delivery to be easy, accurate and reliable
Questions?