METIS Second Master Training & Seminar Augmentation Systems Available in Egypt By Eng. Ramadan Salem M. Sc. Surveying and Geodesy Email: ramadan_salem@link.net Page 1
Augmentation Systems Available in Egypt: Plan of the Presentation 1. GNSS Error Sources 2. What Is Augmentation? 3. Benefits of Augmentation 4. Different Types of Augmentation Systems Available in Egypt 5. Comparing Free EGNOS vs. Commercial OmniSTAR VBS The METIS project is managed by the European GNSS Supervisory Authority through Euro-MED GNSS I project Page 2
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) Page 3
What Is Augmentation? GNSS Satellites Reference Receiver Calculates Position Compares to its own fixed position Calculates Error Transmits Corrections User s Receiver Calculates Position User Receiver Applies Correction to Calculated position Page 4
Benefits of Augmentation GPS-Like Signal Differential Corrections Use/Don t Use Message + ACCURACY + AVAILABILITY + CONTINUITY + Integrity Page 5
Augmentation Systems Available in Egypt 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 Page 6
(1-A) Post-Mission Diff. Positioning GNSS Satellites The data is collected at the same time by the 2 receivers having the same record interval. Base Receiver (Known Point) Then data is downloaded to PC Rover Receiver (Unknown Point) Rover (Unknown) Position Post-Processing Software The software matches the time tags, detects error at base station and subtracts the same error at the same time from the roving file. Page 7
(1-B) Real-Time Diff. Positioning GNSS Satellites Both Base and Rover observe at least 4 common satellites at the same time Page 8 Base Receiver (Known Point) computes the satellite range corrections Local (e.g. RTK) Real-Time Corrections Telemetry Link Global (e.g. OmniSTAR) Rover Receiver (Unknown Point) applies the corrections to their measured ranges, using the corrected ranges to compute their position
(1-B- i) Real-Time Kinematic (RTK) RTCM Messages Rover Radio Antenna GPS Antenna Page 9 Choke Ring Antenna Base Station Base Radio Antenna Base Radio Rover Radio 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 (VBS)) Method Meter-Level Accuracy User Segment: Single Frequency Receiver Wide-Area Carrier Phase Positioning Methods Decimeter-Level Accuracy User Segment: Dual Frequency Receiver The OmniSTAR L-Band Signal: - First provided in Australia in 1995. - Available in the USA since 1997. Page 10
OmniSTAR System Concept Component of Work 6 L- Band Geostationary Satellite GPS Satellite DGPS Up-Link Atmospheric Correction Message GPS Signal Virtual Base Station (VBS) OmniSTAR GPS Subscribed Land or Air User 6 Uplink Station 3 Network Control Centers 100 OmniSTAR GPS Monitor Sites Page 11
OmniSTAR Worldwide Coverage Page 12
OmniSTAR EA-SAT Coverage Map Satellite EA-SAT (Europe) Frequency 1535.1525 MHz Baud Rate 1200 Page 13
Advantages of OmniSTAR VBS 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. Page 14
Wide-Area Carrier Phase Positioning Methods Wide Area Carrier Phase Positioning Methods Multiple Reference Station Precise Orbit and Clock Method OmniSTAR-HP (Land) StarFix-HP (Marine) Note: The distance to the closest station is more than 500 km StarFix GSS (Marine) SkyFix XP (Marine) Not location dependent Page 15
(3) Pseudolites (Beacons) In Egypt 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. Page 16
Pseudolite Concept of Work GPS Satellite A Pseudolite works as a complete ground-based satellite. Difference between GPS satellite and pseudolite: Pseudolite position is described in geographical terms not in the orbital elements used by satellites. satellite signal to Pseudolite satellite signal direct to user 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. Page 17 Pseudolite at a known point on the ground User
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. Station Location Frequency (khz) Power (Watt) Expected Range at 75 μv/m (NM) Mersa Matrouh 31º 21 33 N 27º 14 48 E 307.0 200 150 Alexandria 31º 09 14 N 29º 52 47 E 284.0 200 150 Port Said 31º 16 22 N 32º 17 32 E 290.0 200 126 Ras Gharib 28º 21 07 N 33º 06 37 E 298.0 200 150 Ras Umm Sid 27º 50 56 N 34º 18 50 E 293.5 200 126 Quser 26º 08 16 N 34º 15 39 E 314.5 500 260 Page 18
Pseudolite Coverage In Egypt Mersa Matruh Alexandria Port Said Ras Gharib Ras Umm Sid Quseir Page 19
(4) EGNOS 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. Page 20
EGNOS Concept of Work GNSS Satellites 3 Geo Satellites AOR-E / IND-W/ ARTEMIS SBAS Message Augmented Navigation EGNOS Wide Area Network (EWAN) 33 Reference & Integrity Monitoring Stations (RIAM) Integrity & Ranging + Corrections 6 Navigation Land Earth Stations (NLES) 4 Mission Control Centers (MCC) Page 21
EGNOS vs. OmniSTAR VBS Test 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 Z-MAX DGPS MAX Page 22
EGNOS vs. OmniSTAR VBS Test CDA-3 Antenna Antenna Splitter EGNOS OmniSTAR Page 23
EGNOS vs. OmniSTAR VBS Test 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). Page 24
EGNOS vs. OmniSTAR VBS Test 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. Page 25
EGNOS vs. OmniSTAR VBS Test 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 28 th of February, 2005 End Time: 00 UTC on 1 st of March, 2005 Mask Angle: 5 Record Interval: 1 sec Observations with PDOP > 6 are excluded from graphs and statistics. Page 26
Number of Viewed & Used Satellites Page 27
Used Satellites PRN Numbers OmniSTAR VBS: 01 02 03 04 07 08 10 11 13 14 15 16 18 19 20 21 22 24 25 26 27 28 29 For EGNOS: 01 03 04 07 08 10 11 13 14 15 16 18 19 20 22 24 25 26 27 28 29 EGNOS Min. Max. VBS Min. Max. # Sat. Viewed 9 12 # Sat. Viewed 9 12 #Sat. Used 4 9 #Sat. Used 7 11 Page 28
Used Satellite Availability over Time OmniSTAR EGNOS Page 29
DOP Values Over Time EGNOS Min. Max. VBS Min. Max. PDOP 3.0 98.0 PDOP 1.3 2.5 HDOP 0.9 7.7 HDOP 1.4 14.8 VDOP 1.1 12.7 VDOP 1.0 2.2 Page 30
DOP Values Over Time Page 31
E, N and Alt. over Time VBS Min. Max. Average E -1.293 1.182 0.185 N -3.101 0.515-0.724 Alt. -3.372 4.028 0.082 EGNOS Min. Max. Average E -3.87 2.02 0.041 N -3.60 3.86-0.0781 Alt. -3.97 10.03 1.230 Page 32
E, N and Alt. over Time N E Alt. Page 33
E, N and Alt. over Time Average E, N and Alt. for each 1hr over Test Period EGNOS OmniSTAR VBS Page 34
Scatter Plot over Test Period For EGNOS: 2D Offset Distance (m) = 0.0885 m For OmniSTAR VBS: 2D Offset Distance (m) = 0.7475 m Page 35
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