GPS Technologies in PPUs Clarifying some misunderstandings. A presentation to the Latin American Forum, September Peter Selwyn Chief Executive

Transcription

1 GPS Technologies in PPUs Clarifying some misunderstandings A presentation to the Latin American Forum, September 2013 Peter Selwyn Chief Executive Photo courtesy of Flinders Ports

2 Our Company Our staff: Experienced mariners Marine electronics experts PPU experts Our customers: Government Marine Departments Port Authorities Terminal operators Pilotage companies Independent pilots Large oil & gas corporations Coast Guards In over 25 countries

3 Experience Producing PPUs since 2003 Supported by world-leading software, electronics and GPS experts Presented and published a wide variety of industry papers Industry members of bodies such as IHMA

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5 What is a PPU (Portable Pilot Unit)? Is it the display? (Laptop, Tablet, ipad, etc) Is it the Software? (Basic, Advanced) Is it the sensor equipment? Ship-based (normally via AIS interface) Wired (AIS Cable) Wireless (AISPilot) Independent GPS Single GPS antenna Without gyro assistance (LightPilot) With gyro assistance(channelpilot) Semi independent heading/rot Dual GPS antenna (HarbourPilot) Fully independent heading/rot

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8 Wired and Wireless AIS connectors

9 Single antenna GPS with and without gyro assistance LightPilot (no gyro) ChannelPilot (with gyro assistance)

10 Dual antenna (fully independent system) HarbourPilot

11 Single antenna, gyro assisted

12 The PPU is the combination of all the above Only as good as the data from the sensors Only as good as the software being used Only as good as the chart on which it s displayed Only as good as the level of training of the user to use it This presentation will concentrate on the data generation aspects A lot of confusion over accuracy and terminology

13 How accurate is my PPU Position? Basic GPS (iphone/android/handheld GPS) 15-30m Basic GPS with DGPS corrections 10-15m High quality GPS 2-3m High quality GPS with DGPS corrections <1m RTK corrections 2-20cm

14 But - what s the most important factor? Any GPS will give you a position But knowing the position only tells you where the antenna is It doesn t tell you where the bow or the stern are The most important factor is: HEADING (Proa)

15 What happens if we don t know heading? Ship points in wrong direction on screen Position showing with 15m error circle

16 What happens if we don t know heading? Position with 2m error

17 What happens if we don t know heading? If ship is moving, the heading will follow COG, not true heading

18 What happens if we don t know heading? If we add the true heading, with ROT as well, we get a much better image of what is happening

19 Where does heading come from? Ship s gyro via AIS Pilot Plug Gyro error Whole-degree rounding Gyro-assisted PPU Single-antenna system with gyro assistance Eg ChannelPilot Fully independent PPU Dual antenna system Eg HarbourPilot

20 Antennas 1.6m apart = 0.1 deg error (95%) Error at bow (250m distance) = <0.5m

21 A little about terminology? GNSS (Global Navigation Satellite System) GPS American System GLONASS Russian System Beidou (Compass) Chinese System Dual Frequency L1/L2 Making Position more accurate DGPS (Ground-based) SBAS (Space-Based Augmentation Systems) (WAAS/EGNOS/MSAS/GAGAN) RTK (Real Time Kinematic)

22 Do I need GLONASS as well as GPS? For position accuracy absolutely NO! Glonass by itself is less accurate than GPS GPS + GLONASS is not possible (clock systems are incompatible) Only advantage is it gives an alternative system when GPS reception is poor For heading accuracy Yes. More data for heading computer to use Heading is calculated quicker and more reliably Allows for greater antenna separation (dual antenna systems) Single antenna systems Glonass does very little except provide redundancy

23 Do I need Dual Freq (L1/L2)? For position accuracy a qualified yes, but not much Civilian users cannot use the all the data from the L2 freq Addition of L2 data helps to reduce Ionospheric errors For heading accuracy Yes. More data for heading computer to use Heading is calculated quicker and more reliably Allows for greater antenna separation in dual antenna systems Single antenna systems for pilotage Dual frequency is not so important

24 Do I need better position accuracy? Yes but not so much for the absolute positional information itself How accurately do you measure your antenna offsets? How accurate is the chart? Pilots use their eyes Velocity data is improved if position is more accuracy

25 How do I make heading more accurate? Don t rely on AIS (notoriously poor data) Single antenna PPU Make sure it s gyro integrated (eg ChannelPilot) Dual antenna systems By putting the antennas further apart Add GLONASS for more data Add L2 frequency for more data

26 In summary 1 Dual antenna systems For Position accuracy DGPS is fine. RTK adds a little but really only to velocity For Heading accuracy Glonass and dual freq allow greater antenna separation hence more accurate Single antenna systems Get the best you can Be gyro-integrated

27 In summary 2 Most important of all.. Don t forget to look out the window This is not a video game!!! It s just an aid no different from any other aid

28 MUCHAS GRACIAS MUITO OBRIGADO THANK YOU