# Presentation: 054652

## CORS USERS FORUM Towards Real-Time Positioning

- Richard Snay
- NOAA’s National Geodetic Survey
- CGSIC Meeting
- Long Beach, CA
- September 13, 2005

## Agenda

- 1:30 CORS/OPUS: Status & Overview
-         Richard Snay, NOAA’s National Geodetic Survey
- 1:45 EarthScope’s Plate Boundary Observatory
- 	    Greg Anderson, UNAVCO, Inc.
- 2:05 Post-Processing Versus Real-Time GNSS
- 	    Georg Weber, German Federal Agency for Cartography
-          and Geodesy
- 2:25 The International GNSS Service—Progress Towards Real-Time
-          Mark Caissy, Natural Resources Canada
- 2:45 CORS/OPUS: Future Prospects
-          Charles Schwarz, NOAA’s National Geodetic Survey
- 3:00 Question & Answer Session
- 3:20 Break
- 3:35 Interactive Sessions within Small Discussion Groups
- 5:00 End

## Interactive Sessions (3:35 – 5:00 pm)

- Towards real-time CORS products and services
-      Charles Schwarz, Miranda Chin, and Bruce Sailer
- B. OPUS, UFCORS, and other CORS utilities
- 	 Tom Soler, Dale Pursell, and Marti Ikehara
- C. Guidelines for establishing CORS sites
- 	  Giovanni Sella, Don Haw, and Julie Prusky
- D. Ionospheric & tropospheric models
- 	 Tim Fuller-Rowell and Dru Smith

## Continuously Operating Reference Stations

***Continuously Operating Reference Stations***

## CORS OVERVIEW

- National CORS Network contains 667 sites
- Cooperative CORS Network contains 140 sites
- California CORS Network contains 350+ sites
- Combined CORS Network growing at rate of 15 sites per month
- More than 155 organizations participate in the CORS program
- Provides code range (C/A, P1, P2)
- and carrier phase observations (L1, L2)

## CORS APPLICATIONS

- Postmission Static Positioning (cm-level accuracy with a few hours of data, dm-level accuracy with one minute of data)
- Postmission Kinematic Positioning (dm-level accuracy for an aircraft, boat, or land vehicle)
- Geophysics / Crustal Motion
- Meteorology / Water Vapor in Atmosphere
- Space Weather / Free Electrons in Ionosphere

## CORS NETWORK NOW CONTAINS 6 IRAQI SITES

***Established by ***
***U.S. Army***

- Several CORS in Hurricane Zone Now
- Collecting 1-Second GPS Data to Support Airborne Mapping

## CORS ACCOMPLISHMENTS in FISCAL YEAR 2005

- Combined CORS network grew by more than 240 sites. (Thanks mainly to EarthScope’s Plate Boundary Observatory and to RTK networks being established by state and local governments.)
- Accuracy of NGS-produced orbits improved by 37.5%         (4 cm  2.5 cm).
- NOAA now using CORS data to nowcast Total Electron Content (TEC) over CONUS every 15 minutes.
- NOAA now using CORS data operationally to nowcast precipitable water vapor over CONUS every hour.
- NOAA now validates positional coordinates of Cooperative CORS sites daily (previously it was done monthly).
- The Online Positioning User Service (OPUS) processed 150,000 GPS data sets.

## US-TEC Product

***   ****Since November 2004, an experimental product characterizing the ionospheric total electron content (TEC) over CONUS has been running in real-time at NOAA’s Space Environment Center (SEC)**
**Uses a Kalman filter and ingests ground-based GPS data to produce 2-D maps of TEC **
**Product evolved from a collaboration between NOAA’s National Geodetic Survey (NGS) and SEC**

**Real-time ionospheric maps of total electron content every 15 minutes. Currently uses about 60 real-time GPS stations from the CORS network**** **

## Slant-Path TEC Maps

**The work horse of the product consists of 2-D maps of slant path TEC over the CONUS for each GPS satellite in view, updated every 15 minutes **
**estimates of the group delay or phase advance for the GPS signals anywhere in the CONUS**

- Sat. 1

- Sat. 5

- Sat. 14

- Sat. 29

**...****.****etc**

## US-TEC Applications

-  Ionospheric correction for single frequency GPS and NDGPS positioning
- Dual-frequency integer ambiguity resolution for rapid centimeter accuracy positioning

## Plans for US-TEC

**Product approved for transition to full operations in Spring 2006**
**Parallel data stream from CORS-East and CORS-West will increase reliability**
**Increase number of real-time stations over CONUS by including WAAS stations, plus stations operated by NOAA’s Forecst Systems Lab **
**Include Canadian-sponsored IGS stations to improve poleward coverage**
**Increase cadence to 5 minutes**
**Provide short-term forecast (10 to 30 minutes) to bring up to, or just beyond, real-time**

## ON THE CORS HORIZON

**Within the next 3 months**
- 	* 15 Mexican sites will join the CORS network.
- 	* OPUS-DB (database) will allow users to archive their results in the National Geodetic Survey’s database.
- 	* NOAA will release new guidelines for establishing CORS
-            sites and managing CORS information.

## Mexican National Active Geodetic Network

## OPUS-DB OBSERVATION DATA STREAM

- Observation log

**OPUS-DB**** OBSERVATION DATA STREAM**

- description form

- photo(s)

- NGS website:
- OPUS-DB

- NGS DATABASE

- NGS magic

**Notes:**
In contrast, OPUS-DB is very streamlined; all the work takes place on the NGS-side of the internet

Of course, that puts the burden of effort on NGS.

## NEW CORS GUIDELINES

**GOALS**:
- Improve quality of CORS data
- Focus attention on CORS meta-data requirements

**Selected Items**:
-    * Team established to evaluate new sites more rigorously
-        before including them into the CORS network
-    * Encourage more stable sites
-    * Avoid multipath-prone sites
-    * Radomes not recommended except ...
-    * Track all satellites regardles of their health status
-    * Track satellites to lower elevation angles
-    * Provide suite of photos for each site

## ONGOING CORS RESEARCH

- 	* Exploring the use of NTRIP to stream GPS data from selected CORS via the Internet.
- 	* Developing OPUS-RS (rapid static) that will enable users to obtain positional coordinates with cm-level accuracy using only 15 minutes of data

## PROPOSED POLICY FOR STREAMING GPS DATA VIA THE INTERNET

- NOAA’s National Geodetic Survey (NGS) is exploring the possibility of streaming GPS data (not correctors) from selected Continuously Operating Reference Stations (CORS) via the Internet.
- These data will be publicly available and free of direct user fees.
- NGS is openly distributing these data to enable other organizations to provide location based services relative to the National Spatial Reference System.
- Users may also apply these GPS data to
- 	* monitor the distribution of free electrons in the atmosphere,
- 	* monitor the distribution of precipitable water vapor in the atmosphere, and
- 	* record the passage of seismic waves.
- While these GPS data may be applied to track the path of a moving platform--such as an aircraft, water vessel, or land vehicle–these data will not possess sufficient “integrity” to support a robust navigation service.