NYSDOT CORS Past, Present and Future

1
NYSDOT CORS Past, Present and Future

• Ron Frederiks
• rfrederiks_at_dot.state.ny.us

2
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

3
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

4
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
5
Trilateration
Ideally, the three spheres will intersect at a
discrete point.
3 seconds out
5 seconds out
7 seconds out
6
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

7
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.

8
Differential GPS

• Two receivers track the SAME signals and,
  therefore, errors at the SAME time

User
Base
9
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

10
NGS CORS Network
11
Data Availability (OSPA)
12
Data Availability (SYCN)
13
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

14
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)

15
NYSDOT CORS
16
CORS on 3/30/2006
17
Data Availability
18
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

19
CORS Installation
20
CORS Hardware
21
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

22
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

• 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
23
Servers
Site server 24
Network server 25
Site server 45
24
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

25
Envisioned Web Delivery
NGS
NGS
Spider Web
26
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

27
RTK Clusters
28
GPS Technology
GPS Rovers Tracking From a GPS Base Station or
CORS Station
Use of GPS for Quality Control on ATVs
29
Methods ForMachine Navigation Systems
Robotic Total Station Tracking a Prism (Could
Include Laser Guidance)
GPS Receivers Tracking From a GPS Base Station or
CORS
30
RTK Saratoga test of Cell
31
Verizon Coverage
32
Future of NYSDOT Cors
33
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

34
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

35
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

36
ABGPS Antenna
37
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

38
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

39
GrafNav Software
40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
Plotted in GIS
44
Fall 2005 Flights in GIS
45
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

46
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

47
Questions?