NYSDOT CORS Past, Present and Future Ron Frederiks rfrederiks@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 40 milliseconds 70 milliseconds 60 milliseconds

Ideally, the three spheres will intersect at a discrete point. Trilateration Ideally, the three spheres will intersect at a discrete point. 3 seconds out 5 seconds out 7 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 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

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 Control Sites/ Log Static Data Distribute Static Data Produce Real Time Data Streams with Corrections Distribute Real Time Data Streams Distributes Static Data 18 Stations Distribute: 1 sec hourly RINEX Static Data Single Baseline RTCM Nearest Site RTCM Single Cell Network RTCM Automatic Cell Network RTCM 18 Stations Real Time Network Processing Two Site servers control 18 sites each, store raw static data and distribute static data products. Network server controls real time network and distributes real time data products to Proxy Server. 2 cluster servers process the real time network corrections. Proxy server makes static and real time data streams available to GPS users. 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 Log .5 sec. Static data ½ hourly files Stream 1 sec. Raw Data for RTK net processing

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 NGS Spider Web

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

GPS Technology GPS Rovers Tracking From a GPS Base Station or CORS Station Use of GPS for Quality Control on ATVs

Methods For Machine Navigation Systems GPS Receivers Tracking From a GPS Base Station or CORS Robotic Total Station Tracking a Prism (Could Include Laser Guidance)

RTK Saratoga test of Cell

Verizon Coverage

Future of NYSDOT Cors

NYSDOT CORS Mission Ensure Accuracy By: Ensure Reliability 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

Project Area Flight Line Diagram Strips of photos laid out to maximize coverage and allow for Photogrammetric Mapping It is impossible to fly the job exactly as it is laid out ABGPS allows us to see if the project is flown to within allowable tolerances Early detection of errors (over the allowed tolerances) allow NYSDOT to request a re-flight

ABGPS Antenna

What is ABGPS? ABGPS stands for Airborne Global Positioning System GPS antenna mounted on top of aircraft fuselage Time stamped “event marker” created when aerial camera collects image

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

GrafNav Software

Plotted in GIS

Fall 2005 Flights in GIS

ABGPS Summary ABGPS used in Photogrammetry to: Provide early QA/QC of aerial photography Reduce the amount of ground control required to do large scale mapping Differential correction of GPS data is required for Photogrammetric accuracies The NYSDOT CORS network provides the base station data needed for differential correction NYSDOT CORS will be a vast improvement over the NGS CORS network

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?