# Presentation: 491026

## Real-Time and Near Real-TimeGPS Products and Services from Canada

**Y. Mireault, P. Tétreault, F. Lahaye, P. Collins, **_**M. Caissy**_
- Geodetic Survey Division, Natural Resources Canada (GSD/NRCan)
**http://www.geod.nrcan.gc.ca**
**IGS Analysis Center Workshop 2008**
- June 2-6, 2008
- Miami Beach, Florida, USA

## Outline

- NRCan Ultra Rapid Products (EMU)
- CSRS Precise Point Positioning Service (CSRS-PPP)
- Canadian RT GPS Tracking Network
- Canadian High Precision RT GPS Wide-Area Correction Service (GPS·C)
- Final Notes

## 1. NRCan Ultra Rapid Products (EMU)

- Orbits and clocks for RT/NRT usage
- Covers 48h, i.e. 24h estimated and 24h predicted
- Produced **every hour**
- ~1h delay for orbits and ~1.5h delay for clocks
- Submission to IGS every 6h
- Predicted orbits used in** ****GPS·C**
- Estimated orbits and 30-sec satellite clocks used in **NRT PPP**

**1.1 Description**

**Notes:**
1hr delay for orbits includes a 45min waiting period and ~15min processing time. 
Clocks are done after the orbits and takes about 30 minutes, so about 1.5hr total before the clocks are available!

## 1.2 Some Highlights

| Dates | Important Changes and Highlights |
| --- | --- |
| 2000-Mar-20 | Ultra Rapid 1st orbit submission to IGS (3h cycle) |
| 2002-Oct-31 | Ultra Rapid 1st clock submission to IGS (3h cycle) |
| 2006-Oct-31 | Estimating 5-min satellite clocks |
| 2007-Jan-24 | 1h cycle |
| 2007-Oct-10 | Estimating 30-sec satellite clocks |

## 1.3 Precision*

| NRCan Solutions
(EMU) | Orbits* 
(cm) | Clocks*
 (ns) |
| --- | --- | --- |
| Estimated portion (24h) | 3-4a | 0.15a |
| 3h prediction | 5b | 0.5 |
| 6h prediction | 5 | 1 |
| 12h prediction | 6 | 2 |
| 24h prediction | 13 | 4 |

**(*) Orbit and Clock Median RMS when compared to IGS Rapid (IGR)**
**(a) Orbits and clocks are used in NRT PPP**
**(b) Orbits are used in ****GPS·C**

**Notes:**
Comparison is made wrt to IGS Rapid (IGR)!
The 1st line (yellow shaded areas) shows that they are used as input in NRT PPP.
The 2nd line (purple shaded area) shows that it’s used as input in GPS·C.
Since we produce a new orbit every hour, GPS·C gets 4-5cm orbit all the time!
Remember that these numbers are Median RMS and are insensitive to occasional outliers (e.g marginal satellites). 
	We do have problems modeling some satellite orbits at times but we always try to minimize these problems. Processing on a 1-hour cycle sure helps. 
Users are still required to do some internal checks/validation for optimum results

## 2. CSRS Precise Point Positioning (PPP)

- A Web based global positioning service for single GNSS datasets  (currently GPS only; GLONASS planned)
- Initiated in the Fall of 2003 as next-day service (17h delay)
- Delay reduced to **90min** (May 2008) using NRCan Ultra Rapid orbits and 30sec clocks
- Process static or kinematic (both with single or dual frequency data)
- Use of IGS IONEX grids for single frequency processing

**2.1 Description**

## 2.2 CSRS-PPP Usage

**2.2 CSRS-PPP Usage**

## 2.3 CSRS-PPP Static Positioning Corrections	(wrt IGS05)

**2.3 CSRS-PPP Static Positioning Corrections****	****(wrt IGS05)**

**Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470**

**Notes:**
Bars represent mean of 35 (5 stations x 7 days) differences  between CSRS-PPP estimates and IGS05 (SINEX) coordinates all computed with 30sec data with various orbits and clocks products and interpolated clocks as needed.

The thin lines represent formal (1 sigma) standard deviations of those mean represented in standard Excel fashion (i.e., measured from top of bar where for the negative mean the top of bar is its lowest point with the std line going through the bar)

## 2.4 CSRS-PPP Kinematic Positioning Variations (wrt IGS05)

**Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470**

**Notes:**
Bars represent mean of 35 (5 stations x 7 days) differences  between CSRS-PPP estimates and IGS05 (SINEX) coordinates all computed with 30sec data with various orbits and clocks products and interpolated clocks as needed.

The thin lines represent formal (1 sigma) standard deviations of those mean represented in standard Excel fashion (i.e., measured from top of bar where for the negative mean the top of bar is its lowest point with the std line going through the bar)

## 3. Canadian RT GPS Tracking Network

**3.** **Canadian RT GPS Tracking Network**

**Notes:**
You should focus on the CSRS Real-Time stations.
How many Canadian stations are available world wide? All?

## 4. GPS·C: Canadian High Precision RT 			GPS Wide-Area Correction Service

**Pseudorange & Phase Processing from IGS-RT + RT-CACS Stations**
- P3 = (Xsta,**Xsat**) + c **·** ( **dtsta** – **dtsat** ) + **dtrop**          + 
- L3 = (Xsta,**Xsat**) + c **·** ( **dtsta** – **dtsa****t** ) + **dtrop** + **N**  + 
**Xsat **provided by EMU (1h cycle)  ||  IGU (6hr cycle) predictions
**dtsta, dtsat,dtrop,N** estimated in real-time
**Enhancement of the current code-based system**

**4.1 Description ****(1/2)**

**Notes:**
It is an enhancement of the current filtered code-based system
In red are estimated parameters in real-time
In green are the predicted parameters

## 4.1 Description (2/2)

**Modeled Effects**
- Earth & ocean tides
- Station & satellite absolute PCV
- Relativity
- ITRF station velocity
- Phase wind-up
**Parameters Estimated**
- Station and satellite clocks (white noise parameters wrt VRC)
- Station troposphere ZPD (random-walk)
- Constant (float) ambiguities
**RT High Precision Correction Stream**
**X**sat-BRD @ 120sec (linear over 240sec)
- dtsat-BRD @ 2sec

## 4.2 GPS·C Results

## 4.3 GPS·C Development

**Status**
- Access to 50+ real-time stations globally
- Finalizing stress-tests & application robustness improvements
- IOC targeted for Fall 2008  Pilot Project / ESS activities
**Further Refinements to the Phase-based Algorithm & Models**
- YAW model (Kouba, GPS Solutions (online))
- Un-differenced integer ambiguity resolution with **decoupled clocks**
- Define BRD-independent orbit messages
- Define messages for troposphere-mapping grid, satellite DCB’s
- Define messages required for PPP ambiguity resolution

## 4.4 	Day-Boundary Clock Jumps / 	Decoupled Clocks

## 5. Final Notes

**IGS Ultra Rapid Combination**
- Push it to a 3h cycle? Ultimate goal of 1h cycle?
- Reduce delay from 3h to 2h?
- Need more AC clock solutions to improve precision and accuracy!
**Global RT GPS Tracking Network**
- Would provide faster data for Ultra Rapid orbits/clocks turnaround
**Need for ****30sec satellite clocks**** for Rapid and **
**	****Ultra Rapid products (NRT users such as PPP)**

**Notes:**
This is just a wish list regarding IGS Ultra Rapid products.
Most AC are doing 3hr cycle... I think!
Estimated Clock solutions is real weak for IGS Ultra Rapid.
	At most 3-4 ACs only! Sometimes less!

## Information on decoupled clocks

“Isolating and Estimating Undifferenced GPS Integer Ambiguities”,
		Paul Collins, GSD, NRCan

Presented at the Institute of Navigation, NTM 2008, San Diego, 
	January 28-30 2008, session D3.
Look also for the corresponding paper in the ION TNM proceeding.

**“****Isolating and Estimating Undifferenced GPS Integer Ambiguities”**,
- 		***Paul Collins***, GSD, NRCan
- Presented at the **Institute of Navigation, NTM 2008**, San Diego,
- 	January 28-30 2008, **session D3**.
- Look also for the corresponding paper in the ION TNM proceeding.

**Notes:**
This is just a wish list regarding IGS Ultra Rapid products.
Most AC are doing 3hr cycle... I think!
Estimated Clock solutions is real weak for IGS Ultra Rapid.
	At most 3-4 ACs only! Sometimes less!

## Statistics based on processing of  5 min data from 24 hour files 

**for ALGO for GPS Week 1470**

**Notes:**
Bars represent mean of  7 daily std of differences between  between CSRS-PPP estimates and IGS Products computed with 5 min data with various orbits and clocks products
IGS Tropo is products computed by Yoaz

The thin lines represent formal (1 sigma) standard deviations of those mean represented in standard Excel fashion (i.e., measured from top of bar where for the negative mean the top of bar is its lowest point with the std line going through the bar)

## Statistics based on processing of  5 min data from

**Statistics based on processing of  5 min data from**
** ****24 hour files for ALGO for GPS Week 1470**

**Notes:**
Bars represent mean of  7 daily std of differences between between CSRS-PPP estimates and IGS Products computed with 5 min data with various orbits and clocks products
Offset and slope removed from each clock series before differencing
The thin lines represent formal (1 sigma) standard deviations of those mean represented in standard Excel fashion (i.e., measured from top of bar where for the negative mean the top of bar is its lowest point with the std line going through the bar)

## 2.5 CSRS-PPP Static Positioning Corrections 

**(wrt IGS05)**

**Hours**

**Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470**

**Notes:**
Points represent mean of 35 (5 stations x 7 days) differences  between CSRS-PPP estimates and IGS05 (SINEX) coordinates all computed with 30sec RINEX files of various  durations (15min, 30min, 45min, 60min, 90min, 2h, 3h ...) and EMU or IGS (30seec) orbits and clocks products.

## Y. Mireault, P. Tétreault, F. Lahaye, P. Collins, M. Caissy
Geodetic Survey Division, Natural Resources Canada (NRCan 

Natural Resources Canada (NRCan) has been involved in producing and promoting GPS Real-Time (RT) and Near Real-Time (NRT) products and services for more than 10 years.  Key products and services, like 1Hz GPS station data, Ultra Rapid GPS orbits/clocks, GPS Precise Point Positioning (PPP) and GPS corrections (GPS·C), have been developed and refined over the past several years.  This presentation will focus on current RT and NRT products and services developed by NRCan and made available to users in Canada and world wide.

First, a description of the RT GPS tracking network covering Canadian territory and used within GPS·C will be given. Next, NRCan’s hourly Ultra Rapid GPS satellite orbit and 30-sec satellite clock estimation strategy will be presented. Then, we will discuss NRCan’s PPP, a free online post-processing service using IGS and NRCan’s orbits/clocks and IGS IONEX products to allow GPS users world wide to compute better-accuracy positions from their single/dual frequency datasets observed in static/kinematic mode. Finally, an overview of the RT GPS wide-area correction service (GPS·C) distributed nationally through the Canada-wide DGPS will be given.

*Geodetic Survey Division, Natural Resources Canada (NRCan*
*Natural Resources Canada (NRCan) has been involved in producing and promoting GPS Real-Time (RT) and Near Real-Time (NRT) products and services for more than 10 years.  Key products and services, like 1Hz GPS station data, Ultra Rapid GPS orbits/clocks, GPS Precise Point Positioning (PPP) and GPS corrections (**GPS·C**), have been developed and refined over the past several years.  This presentation will focus on current RT and NRT products and services developed by NRCan and made available to users in Canada and world wide.*
*First, a description of the RT GPS tracking network covering Canadian territory and used within GPS·C will be given. Next, **NRCan’s hourly Ultra Rapid GPS satellite orbit and 30-sec satellite clock estimation strategy will be presented. Then, we will discuss NRCan’s PPP, a free online post-processing service using IGS and NRCan’s orbits/clocks and IGS IONEX products to allow GPS users world wide to compute better-accuracy positions from **their single/dual frequency datasets observed in static/kinematic mode**. **Finally, an overview of the RT GPS wide-area correction service (GPS·C) distributed nationally through the Canada-wide DGPS will be given.*

***Real-Time and Near Real-Time GPS Products and Services from Canada***