Antenna Baseline Measurement System 29 January 2010 Mark Phillips, Research Assistant Ohio University, Athens OH Research Intern Naval Research Laboratory

2 Outline Common uses of differential systems What is ABMS Uses of ABMS System construction overview Conclusions Questions Ohio University - Avionics Engineering Center

3 Common Uses of Differential GPS Wide Area Augmentation System (WAAS) Local Area Augmentation System (WAAS) - First certified LAAS installed at Newark NJ Ohio University - Avionics Engineering Center

4 Wide Area Augmentation Systems 38 Reference Stations 3 Master Stations 4 Ground Earth Stations 2 Geostationary Satellite Links 2 Operational Control Centers Currently Available in North America Reference Stations collect GPS Data Master Stations collect data from reference stations and creates correction message Correction Messages is Broadcast to the Geostationary Satellites Satellite Orbits Clock Drift Atmospheric WAAS Capable GPS Receivers then Correct the GPS Message * FAA Eastern Services Area NAVAIDS Meeting March 2009

5 Local Area Augmentation System Designed to replace Instrument Landing Systems (ILS) for precision approach and Landing Composed of 3 subsystems –Satellite –Ground –Airborne Navigation Performance requirements –Must meet three-tiered structure of ILS Approach Services –ICAO Ground Based Augmentation System Standards

6 What is Antenna Baseline Measuring System? (ABMS) Real time kinematic (RTK) System that uses the GPS technique of double differencing Measures precise distances between the phase center of two antennas. Can give a accurate relative frame of reference or given a surveyed point can give accurate positioning with respect to GPS coordinate system. Ohio University - Avionics Engineering Center

7 How the System Works Components - 1 Reference Box (REF) - 1 Rover Box (ROV) - 1 User computer with Matlab REF and ROV communicate observation files wirelessly to user computer. The user computer calculates the baseline between the antennas and displays result to the screen. Ohio University - Avionics Engineering Center

8 System Illustration Ohio University - Avionics Engineering Center ROV REF GPS Observation file1 GPS Observation file 2 Computer Calculated Baseline

9 Examples Of Uses To End Users Precision local area coordinate frame measurements - Precision surveying - Precise position of array elements for radar - Real time truth reference system Ohio University - Avionics Engineering Center

10 Example Application to Aviation Precision Landing of UAV’s Ability to calculate a precise 3D vector from aircraft to runway on approach Able to perform with very little ground based infrastructure or human input. Ohio University - Avionics Engineering Center

11 Precision Landing Ohio University - Avionics Engineering Center baseline

12 Potential in Flight Applications Calculate and track multiple baselines once other system users come available. Giving each aircraft a ground based tracking system independent position of other aircraft relative to its position. If GPS reference stations were updated they could be used in differential GPS calculations. Ohio University - Avionics Engineering Center

13 UAV Relative In Flight Positioning Ohio University - Avionics Engineering Center Baseline 1 Baseline 2 Differential Corrections

14 User Screens Ohio University - Avionics Engineering Center

15 What My Role Has Been? Complete computer replacement on boxes Novatel OEM 4 and BeagleBoard hardware integration Miniaturization Act as an interface between Naval Research Lab (NRL) and Ohio University AEC department System testing –Accuracy –System Reliability Ohio University - Avionics Engineering Center

16 Miniaturization (Old System) Ohio University - Avionics Engineering Center

17 Miniaturization What's been done? New smaller computer Removed Novatel OEM4 from factory case Integrated Novatel patch antenna ground plane in to top of the box Created a custom expansion and communication board for Novatel-computer communication Utilized external mobile power supply Ohio University - Avionics Engineering Center

18 Miniaturization (new system) Ohio University - Avionics Engineering Center

19 Stargate Computer Ohio University - Avionics Engineering Center

20 Stargate Specifications 32-bit, 400 MHz Intel PXA255 XScale RISC processor. SA1111 StrongARM companion chip for multiple I/O access. 32 MB of Intel StrataFlash. 64 MB of SDRAM. Type II CompactFlash slot. 16-bit PCMCIA slot. 51 pin expansion connector Ohio University - Avionics Engineering Center

21 BeagleBoard Computer Ohio University - Avionics Engineering Center

22 BeagleBoard Specifications 600MHz ARM Cortex-A8 (>1GHz ARM11 MIPS) NEON and VFP extensions for additional acceleration Programming: gcc compiler for ARM CortexA8 Programming: free, non-commercial TI compiler for C64x+ Utilities: serial and USB boot-loader tools Ohio University - Avionics Engineering Center

23 Advantages BeagleBoard is completely open source Not limited to Stargates Operating System Now running a full version of xUbuntu Linux Faster CPU Expandable and Upgradeable –Current Revision C3 Ohio University - Avionics Engineering Center

24 Future Development Compile user computer Matlab code to C and let each ROV box calculate it’s own baseline Make system work with multiple ROV boxes Make user computer passive and able to select multiple boxes and view baselines between the multiple boxes Ohio University - Avionics Engineering Center

25 Conclusions ABMS is a new form of differential GPS Potential applications are vast New system is robust and able to handle multiple applications Future work and implementations are being tested currently Ohio University - Avionics Engineering Center

Questions