NYSDOT CORS Past, Present and Future

Ron Frederiksrfrederiks@dot.state.ny.us

Lots of Acronyms!!!!!!

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

Satellite Ranging

Measuring the distance from a satellite Measuring the travel time of radio signals Signal travels at the speed of light

60 milliseconds70 milliseconds

40 milliseconds

TrilaterationIdeally, the three spheres will intersect at a discrete

point. 3 seconds out

7 seconds out

5 seconds out

Accuracy of GPS

Depends on several variables Time spent on measurements Design of receiver Relative positions of satellites

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

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.

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 Two receivers track the SAME signals and,

therefore, errors at the SAME time

Base

User

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

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

What is the NYSDOT CORS?

Initially, a Network of 36

Stations Across NYS

Intended Benefits of CORS 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

Network Server

Site Server

user2

Cluster Server(s) Cluster Server(s)

RTK Proxy ServerRTK Data distribuiton

18 Stations

18 Stations

Site Server

user2

Control Sites/Log Static Data Distribute Static Data

Produce Real Time Data Streams withCorrections

Real Time Network Processing

Distribute Real Time Data Streams Distributes Static Data

Log .5 sec.Static data½ hourly filesStream 1 sec. Raw Data for RTK net processing

Distribute:•1 sec hourly RINEX Static Data•Single Baseline RTCM•Nearest Site RTCM•Single Cell Network RTCM•Automatic Cell Network RTCM

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

Servers

Site server 45

Site server 24

Network server 25

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

NGS

Publication of Real Time Kinematic (RTK) Corrections

Automated Publishing of RTK Correction via Internet IP 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 Ensure Accuracy By:

Network Positions Monitored by NGS & by DOT CORS Software Station Positions Processed Against National Spatial Reference

Network Station Positions Reliant on Continuous Network Monitoring, not Single

Station Coordinate Ensure Reliability By:

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: 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

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 Specifically designed for differential correction

of ABGPS data

Plotted in GIS

Fall 2005 Flights in GIS

In Conclusion

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?