metis second master training & seminar

METIS Second Master Training & Seminar, Cairo (Egypt), 06-07.11.2007

METIS Second Master Training & Seminar

Augmentation Systems Available in Egypt

ByEng. Ramadan Salem

M. Sc. Surveying and Geodesy

Email: [email protected]


The METIS project is managed by the European GNSS Supervisory Authority through Euro-MED GNSS I project

1. GNSS Error Sources2. What Is Augmentation?3. Benefits of Augmentation4. Different Types of Augmentation Systems Available in Egypt5. Comparing Free EGNOS vs. Commercial OmniSTAR VBS

Augmentation Systems Available in Egypt:Plan of the Presentation


GNSS Error Sources

GNSS Satellites

User’s Receiver Calculates Position

• Errors in calculated position:– Multipath– Ionospheric & Tropospheric Delays– Satellite Clock and Orbit Errors– Receiver Clock and Noise Errors– Selective Availability (S/A) if any (GPS Only).

– Dilution of Precision (DOP)


User’s Receiver Calculates PositionReference Receiver

Calculates Position

Compares to its own fixed position

Calculates Error

Transmits Corrections

Applies Correction to Calculated position

What Is Augmentation ?

User Receiver

GNSS Satellites


GPS-LikeSignal

DifferentialCorrections

Use/Don’t UseMessage

+ ACCURACY+ AVAILABILITY+ CONTINUITY

+ Integrity

Benefits of Augmentation


1. Differential Positioning:A. Post-Mission.B. Real-Time:

i. Local Coverage (RTK)ii. Global Coverage (OmniSTAR VBS & HP).

2. Ground-Based Augmentation System (GBAS)• Pseudolite (Beacons)

3. Space-Based Augmentation System (SBAS)• EGNOS

Augmentation Systems Available in Egypt


Then data is downloaded to PC

(1-A) Post-Mission Diff. Positioning

Base Receiver(Known Point)

Rover Receiver(Unknown Point)

GNSS SatellitesGNSS Satellites

The software matches the time tags, detects error at base station and subtracts the same error at the same time from the roving file.

The data is collected at the sametime by the 2 receivers having thesame record interval.

Post-ProcessingSoftware

Rover (Unknown)Position


(1-B) Real-Time Diff. Positioning

Base Receiver(Known Point)

Rover Receiver(Unknown Point)

GNSS SatellitesGNSS Satellites

computes the satellite range corrections

applies the corrections to their measured ranges, using the corrected ranges to compute their position

TelemetryLink

Global(e.g. OmniSTAR)

Global(e.g. OmniSTAR)

Local(e.g. RTK)

Local(e.g. RTK)

Real-Time Corrections

Both Base and Rover observe at least 4 common satellites at the same time

METIS Second Master Training & Seminar, Cairo (Egypt), 06-07.11.2007Base Station

Base Radio

Rover Radio Antenna

GPS Antenna

Rover Radio

(1-B- i) Real-Time Kinematic (RTK)

Base Radio Antenna

RTC

M M

essa

ges

Choke Ring Antenna

• According to RTCM Message Type:– RTK Remote: Centimeter Accuracy– DGPS Remote: Sub-meter Accuracy

• Data Link: a radio link, telephone line, cellular phone or any other medium that can transfer digital data.


(1-B- ii) OmniSTAR Services Types

Virtual Base Station Virtual Base Station ((VBSVBS) Method) Method

Meter-Level Accuracy

WideWide--Area Carrier Phase Area Carrier Phase Positioning MethodsPositioning MethodsDecimeter-Level Accuracy

The OmniSTAR L-Band Signal:- First provided in Australia in 1995.- Available in the USA since 1997.

Segment:UserSingle Frequency Receiver

Segment:UserDual Frequency Receiver


OmniSTAR System Component

Atmospheric Correction Message

GPS Satellite

SubscribedLand or Air User

3 Network Control Centers

100 OmniSTARGPS Monitor Sites

6 L- Band Geostationary

Satellite

OmniSTAR Concept of Work

GPS Signal

DGPS Up-Link

6 Uplink StationOmniSTAR GPS

Virt

ual B

ase

Stat

ion

(VB

S)


OmniSTAR Worldwide Coverage


Baud RateFrequencySatellite12001535.1525 MHzEA-SAT (Europe)

OmniSTAR EA-SAT Coverage Map


• Provides Meter-level Accuracy Real-Time positioning using pseudorange code observations.

• Suitable for Moving Applications: the reference station follows the user around.

• Regular Accuracy over The Entire Coverage Area.

• Highly Reliable: It is not dependent on any single reference station.

• No position jumps: VBS gradually changes the contribution of any reference station in the position solution, as the user moves.

• Correction data is available for all GPS satellites in view at the user’s location.

Advantages of OmniSTAR VBS


OmniSTAROmniSTAR--HP HP ((LandLand))

StarFixStarFix--HP HP ((MarineMarine))

Multiple Reference Multiple Reference StationStation

Precise Orbit and Precise Orbit and Clock MethodClock Method

Wide Area Carrier Phase Wide Area Carrier Phase Positioning MethodsPositioning Methods

StarFixStarFix GSS GSS ((MarineMarine))

SkyFixSkyFix XP XP ((MarineMarine))

Wide-Area Carrier Phase Positioning Methods

Note: The distance to the closest station is more than 500 km

Not location dependent


• In 1997, Egypt Ports and Lighthouse Authority (PLA) established marine differential GPS radio-beacon service,

• These six stations are in service since 1998(Egyptian notice to mariner number 8/1998 published by PLA on 17/9/1998).

• Cover the two coastlines along the Mediterranean and the Red Sea.

Objective:To provide safe GPS navigation to vessels approaching the Egyptian water and the Suez Canal.

Each DGPS radio-beacon contains:• 2 Single Frequency (L1) GPS reference stations,• 2 Integrity Monitors, • 4 GPS Antennas,• High Frequency Communication Station.

(3) Pseudolites (Beacons) In Egypt


Difference between GPS satellite and pseudolite: Pseudolite position is described in geographical termsnot in the orbital elements used by satellites.

GPS Satellite

satellite signal direct to user

satellite signal to

Pseudolite

Pseudolite at a known point on the ground

A Pseudolite works as a complete “ground-based satellite”.

Pseudolite makes the following:1. Measures the satellite signals,2. Creates a precisely timed GPS-like signal,3. Then transmits it over a datalink to user.

User

Pseudolite Concept of Work


Expected Rangeat 75 μV/m (NM)

Power(Watt)

Frequency(kHz)LocationStation

150200307.031º 21´ 33´´ N27º 14´ 48´´ E

MersaMatrouh

150200284.031º 09´ 14´´ N29º 52´ 47´´ EAlexandria

126200290.031º 16´ 22´´ N32º 17´ 32´´ EPort Said

150200298.028º 21´ 07´´ N33º 06´ 37´´ ERas Gharib

126200293.527º 50´ 56´´ N34º 18´ 50´´ ERas Umm Sid

260500314.526º 08´ 16´´ N34º 15´ 39´´ EQuser

Pseudolite Locations in Egypt

They are 6 in number located: • 3 along the Mediterranean: Port Said, Alexandria and Mersa Matrouh.• 3 along the Red Sea: Ras Umm Sid, Ras Gharib and Quser.


Mersa MatruhMersa MatruhAlexandriaAlexandria Port SaidPort Said

Ras GharibRas GharibRas Umm SidRas Umm Sid

QuseirQuseir

Pseudolite Coverage In Egypt


• EGNOS stands for European Geostationary Navigation Overlay Service

• It’s the European version of Satellite Based Augmentation Systems (SBAS)

• It is a joint project of the European Tripartite Group (ETG):– European Space Agency (ESA), – The European Commission (EC) and– The European Organization for the safety of the Air

Navigation (EUROCONTROL).

• ESSP has begun the Initial Operations in July 2005, under contract with ESA.

(4) EGNOS


33 Geo SatellitesGeo SatellitesAOR-E / IND-W/ ARTEMISGNSS SatellitesGNSS Satellites

6 Navigation Land Earth Stations (NLES)

4 Mission Control Centers (MCC)

33 Reference & Integrity Monitoring Stations (RIAM)

EGNOS Wide Area Network (EWAN)

EGNOS Concept of Work

Augmented Navigation

SBASSBASMessageMessage

Integrity & Integrity & Ranging + Ranging + CorrectionsCorrections


DGPS MAXDGPS MAXZ-MAXZ-MAX

Instruments Used in Test:• Z-Max GPS and GNSS Solution Software from Thales

Navigation:For fixing a point and its post-processing software, GNSS Studio, for post-processing.

• 2 DGPS Max GPS receivers from CSI-Wireless

EGNOS vs. OmniSTAR VBS Test


Antenna Splitter

EGNOS OmniSTAR

CDA-3 Antenna



Programs Used:– Autodesk AutoCAD 2004– Microsoft Excel 2003– NMEA Extractor v3.0 with UTM Calculator v1.2 module:

By Ramadan Salem using Microsoft Visual Basic v6.0– Satellite Availability v1.0:

By Ramadan Salem using Microsoft Excel Visual Basic for Applications (VBA).



Graphs Drawn over Time:

– Position Scatter Plot

– Used Satellite Availability

– Number of Viewed and Used Satellites in Position Calculation

– PDOP, HDOP and VDOP Values

– DGPS Age

– ∆Easting, ∆Northing and ∆Altitude over time

– 2D and 3D Error Distance

– Std. Dev. of Computed Latitude, Longitude and Altitude.



Data Collected with the Following Conditions:

– Data collected in form of NMEA Sentences using (GGA, GLL, VTG, ZDA, RMC, GSA, GSV, GST and RRE).

– Test Duration: 11 Hours

• Start Time: 13 UTC on 28th of February , 2005• End Time: 00 UTC on 1st of March, 2005

– Mask Angle: 5°

– Record Interval: 1 sec

– Observations with PDOP > 6 are excluded from graphs and statistics.



Number of Viewed & Used Satellites


1514131110080704030201292827262524222120191816

Max.Min.VBS129# Sat. Viewed117 #Sat. Used

151413111008070403012928272625242220191816

OmniSTAR VBS:

For EGNOS:

Used Satellites PRN Numbers

Max.Min.EGNOS129# Sat. Viewed94 #Sat. Used


Om

niST

AR

EGN

OS

Used Satellite Availability over Time


Max.Min.EGNOS98.03.0PDOP7.70.9HDOP12.71.1VDOP

Max.Min.VBS2.51.3PDOP14.81.4HDOP2.21.0VDOP

DOP Values Over Time


DOP Values Over Time


AverageMax.Min.VBS0.1851.182-1.293∆ E

-0.7240.515-3.101∆ N0.0824.028-3.372∆ Alt.

AverageMax.Min.EGNOS0.0412.02-3.87∆ E

-0.07813.86-3.60∆ N1.23010.03-3.97∆ Alt.

∆E, ∆N and ∆Alt. over Time



∆N

∆E

∆Alt.


EGNOS

OmniSTAR VBS

Average ∆ E, ∆ N and ∆ Alt. for each 1hr over Test Period



Scatter Plot over Test Period

For OmniSTAR VBS:2D Offset Distance (m) = 0.7475 m

For EGNOS:2D Offset Distance (m) = 0.0885 m

Thank youThank You!

http://www.aui.ma/GNSS/metis/

metis second master training & seminar

Documents