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  • 1. locate, communicate, accelerate Now, Now where was I? Dr Chris Marshall chris.marshall@u blox.com chris.marshall@u-blox.com November 2010 IET Buckinghamshire region
  • 2. Where we will go… g • Your many photos • GPS • Assisted GPS • C t Capture and P d Process l t t h l later technology • and what we can do with it • Useful information out of location
  • 3. Imaging and the Web
  • 4. Large photo collections lead to challenges ? Where is the photo I want? Where was this photo taken? Slide 4 © u-blox AG How do I get more from my photos? How can I share the story?
  • 5. Need to add extra data to photos Time Location Subject London Eye Slide 5 © u-blox AG
  • 6. Applications/Websites ready for geotagged images iPhoto 09 PicasaWeb Flickr Slide 6 © u-blox AG
  • 7. locate, communicate, accelerate The Global Positioning System
  • 8. The GPS satellites • US government work started 1973 • First satellite launched 1989 • 24-31 satellites, in 12 hour orbits • Altitude of ~20,200km, speed ~3.9km/s • 6 orbital planes, at 55° inclination Overnight trace of satellite orbits (2004)
  • 9. To find your position using GPS • Just measure the distance to the satellites • And solve. In 2 dimensions… Ra2 = (X-Xa)2 + (Y-Ya)2 Rb2 = (X-Xb)2 + (Y-Yb)2 Ra A B Rb
  • 10. To measure the distance from a satellite… • Measure the time taken for a signal to travel from the satellite to the receiver lf h lli h i • 3ns 1m • Distance = time × c
  • 11. To measure the time accurately • Each GPS satellite transmits a Direct Sequence Spread Spectrum (DSSS) signal • Centre frequency 1.575GHz • Each satellite uses a unique pseudo-random pattern, called a “spreading code” • S th receiver k So the i knows which signal is from which satellite (CDMA) hi h i li f hi h t llit • The spreading code takes exactly 1ms to send and it is sent every ms • 1 023Mb/s 1.023Mb/s • Symbolically (the code is actually 1023 bits long): sent 0ms 1ms 2ms time 3ms 4ms
  • 12. Measuring Propagation Time • The signal has a delay when it arrives at the receiver sent τ received time
  • 13. Measuring Propagation Time • The signal has a delay when it arrives at the receiver sent τ received sent time
  • 14. Measuring Propagation Time • So the receiver scans all time offsets for the signal… sent received replica time
  • 15. Measuring Propagation Time • So the receiver scans all time offsets for the signal… sent received replica time
  • 16. Measuring Propagation Time sent received replica time
  • 17. Measuring Propagation Time sent received replica time
  • 18. Measuring Propagation Time sent received replica time
  • 19. Measuring Propagation Time sent received replica time
  • 20. Measuring Propagation Time sent received replica time
  • 21. Measuring Propagation Time sent received replica time
  • 22. Measuring Propagation Time sent received replica time
  • 23. Measuring Propagation Time sent received replica time
  • 24. Measuring Propagation Time • To find the time where they match (“correlate”) sent received τ replica time
  • 25. In 3 D space • Need to measure 3 di d distances • And solve with 3 equations Ra2 = (X-Xa)2 + (Y-Ya)2 + (Z-Za)2 Rb2 = (X-Xb)2 + (Y-Yb)2 + (Z-Zb)2 Rc2 = (X-Xc)2 + (Y Yc)2 + (Z Zc)2 (X Xc) (Y-Yc) (Z-Zc)
  • 26. But, we also need to know satellite time… • Distance = speed × elapsed time • Satellites have atomic clocks, monitored from the ground, but hand held receivers only have quartz oscillators • An offset δt is caused by the discrepancy between our clock and “GPS time” p • In our 2D example: (Ra + c×δt)2 = (X Xa)2 + (Y-Ya)2 + (Z-Za)2 (X-Xa) (Y Ya) (Z Za) (Rb + c×δt)2 = (X-Xb)2 + (Y-Yb)2 + (Z-Zb)2 c.δt Ra A B Rb c.δt
  • 27. So GPS receivers use 4 satellite signals • In 3 D space we have 4 unknowns X, Y, Z, and δt • 4 measurements, from 4 satellites, and 4 equations… (Ra + c×δt)2 = (X Xa)2 + (Y Ya)2 + (Z Za)2 (X-Xa) (Y-Ya) (Z-Za) (Rb + c×δt)2 = (X-Xb)2 + (Y-Yb)2 + (Z-Zb)2 (Rc + c×δt)2 = (X-Xc)2 + (Y-Yc)2 + (Z-Zc)2 (Rd + c×δt)2 = (X-Xd)2 + (Y-Yd)2 + (Z-Zd)2
  • 28. The location of the satellites • Each satellite tells you where it is in space • Each transmits detailed information about its current orbit “Ephemeris” information. • The basic satellite signal is modulated with a 50 bits/s data message • The message lasts 18s, and i repeated every 30 d is t d 30s • From the ephemeris you can calculate the position of the satellite for the next 2-4hours • So now you can calculate where you are. • This is why a GPS receiver normally needs 30s to start the “Time To First Fix”.
  • 29. Summary of GPS Fundamentals • GPS works by measuring the time it takes signals from satellites to reach a receiver • Spread spectrum signals received all at the same time • separated • measured d • The satellites describe their orbits with a slow additional modulation of the signal which takes ~30s to receive • GPS receivers requires measurements from 4 satellites to calculate their position in 3D space and GPS time
  • 30. Assisted GPS
  • 31. GPS Signals are very weak Earth radius 6,378 km • 45W transmitter , y • 20,180 km away • 10 million times weaker than WiFi signals Slide 31 © u-blox AG
  • 32. It can be difficult to download the data from the satellites • You need a reasonable signal (-142dBm) for f reasonable time ( bl i (>18s) ) • to demodulate the data message • to get ephemeris orbit information • to calculate the satellites’ location • This limits practical performance • Starting in urban canyons • Using indoors Slide 32 © u-blox AG
  • 33. Assisted GPS • Ephemeris information gathered from all satellites, worldwide. f ll lli ld id • Satellite orbit information provided on request to user over communication channel • Current ephemeris data: 1-3KB valid f 2 4 h lid for 2-4 hours Receiver Receiver Internet Satellite it Orbi ase Databa cellular Merge Internet
  • 34. Benefits of Assisted GPS • Faster response • No need to wait 30s to download ephemeris information from the GPS satellites • Better coverage and availability • Do not need to be able to see satellites at -142dBm • Sensitivity can be -147dBm … -155dBm • The device can use more satellites and get better accuracy • As a result of communicating with the satellite monitoring infrastructure at some time
  • 35. Software GPS and Capture and Process technology
  • 36. Software GPS Research • Started in 2000 at Philips Research, Redhill • Consumer devices should be aware of their location • Just as they are aware of the time • C Consumer devices will i d i ill increasingly contain processors and memory i l t i d • Able to share resources with other functions • Continuing improvements from Moore s law Moore’s • The most expensive part of GPS is the baseband processing chip y g position-aware, can we implement baseband p • To make everything p processing in software? • Standard software (C), processor platform, and memory • A ti it acquired b u-blox i 2009 Activity i d by bl in
  • 37. The GPS processing task • GPS is lots of “correlations” • To seek and find (acquire) each weak satellite signal in the noise • To measure the timing of each signal • To demodulate data • Plus high accuracy calculations • For position calculation p 6% 3% 91% Acquisition Measure easu e Fix
  • 38. Conventional, hardware signal processor • Baseband signal processing i.c., containing banks of correlators • Real time signal processing • Signal processed, then discarded • R l time output of “pseudo-ranges” Real ti t t f“ d ” • Fix calculated live from the current pseudo-range values
  • 39. Capture and Process later concept • Separates the two steps, Capture the GPS signal and then Process it later • Capture is instant and takes little energy
  • 40. Capture and Process later concept • Separates the two steps, Capture the GPS signal and then Process it later • Capture is instant and takes little energy • Processing is done later by software running on a PC
  • 41. Application and advantages of C&P using software GPS • Device capture instant – perfect for Cameras • Device capture very low energy – perfect for logging • Processing • Flexibility • Access to PC processor and memory resources • Access to internet and assistance services • Provides the satellite location information
  • 42. Assisted GPS C&P system • Uses internet connection to the PC • Database of historical satellite orbit information built (since Nov 2007) • Worldwide orbit information provided on request for the time when the GPS signal captured
  • 43. Assisted GPS use for Capture and Process GPS • No need to recover the information from the GPS signals themselves • Can use weak satellite signals (<27dB C/N) • Can use short signal samples (e.g. 200ms) • Satellite information conveniently provided over internet • when the processing is carried out and the location desired • not at the time of signal capture. g p • Accurate and correct information for the time of the capture
  • 44. Key benefits of Capture & Process • Instant capture of location data: No waiting No change in user experience g p • Very l low power consumption: Battery lif of months, not hours i life f h h Virtually no impact on battery life. • Lowest cost Only require a GPS radio, antenna and software Slide 44 © u-blox AG
  • 45. Doing things with Capture and Process GPS
  • 46. Adding to a camera • Just add antenna and front end radio • Captured GPS signal data stored with photo Prototyping C17-C1 board Slide 46 © u-blox AG • Processed later when picture uploaded to PC
  • 47. Making a camera accessory • Held and triggered by the camera h shoe h hot h • JOBO PhotoGPS • No waiting when taking a photo • No on-off switch • No manual clock alignment needed (to synchronise the accessory and camera) Slide 47 © u-blox AG
  • 48. Jobo photoGPS • Accessory device • Captures 200ms GPS signal • Stores up to 4000 geotags y • 120mAhour internal battery recharged by USB, lasts up to 4 weeks • PC p ocess g so t a e C processing software • matches captures with photos • GPS position accuracy 10m • finds Reverse geocode • places result in photo EXIF • Distributor MINOX (GB) Ltd, Luton. www.minox.uk Slide 48 © u-blox AG
  • 49. Making a long term location logger with C&P GPS • Energy used only for receiving and storing a GPS Capture - no processing • Energy <50mJ/Capture • Battery life of up to 3 months on just a 130mAhr battery 100000 • Memory for storing Captures • Capture size typically 128KB • 8Gb memory g gives >8000 Captures p • Capacity for a 1 month sampling every 5 minutes Captures per day s 10000 1000 Battery empty Memory f ll M full 100 10 1 0 10 20 30 40 50 60 Days usage 70 80 90 100
  • 50. Taking the students to university • Crossing Europe • 5 days • Captures every 2.5min Slide 50 2010 Copyright © 2007: u-blox AG, 5 December
  • 51. Taking the students to university • Driving around Belgium and the Netherlands d h h l d Slide 51 2010 Copyright © 2007: u-blox AG, 5 December
  • 52. Taking the students to university • Boarding the ferry at Rotterdam d Slide 52 2010 Copyright © 2007: u-blox AG, 5 December
  • 53. We’re all going on a summer holiday… • For 2 weeks • Sailing around Fynn, Denmark • Samples every 3min Slide 53 © u-blox AG
  • 54. locate, communicate, accelerate 51º14.51’N, 000º12.29’W What next? h
  • 55. Maps used to be expensive • Nokia acquired Navteq, for $8.1bn navigation now free on their phones i i f h i h • except that you have to pay for the data traffic for the maps p • TomTom acquired TeleAtlas for $4.3bn • f use with their navigation devices for ih h i i i d i • Google provides maps for free • except that you look at their advertising Ordanance Survey National Library of Scotland Slide 55 © u-blox AG
  • 56. Open Street Map • A map for all, by all • Hosted at UCL www.openstreetmap.org • Supported worldwide • Lots of content • 321 114 contributing users 321,114 • Governments and organisations also making their data available • 2 054 774 073 GPS points 2,054,774,073 i • 829,249,405 nodes 69,300,449 ways • Highlights at www.bestofosm.org Slide 56 © u-blox AG
  • 57. Mapping of photos, good for routes and trips pp g p g p
  • 58. Describe the location by “Reverse Geocoding” • Converts lat-long lat long coordinates into: • Road • Nearest town • Region • Country • Also add nearby Points Of Interest Slide 58 © u-blox AG
  • 59. Location labelling service • Labelling with address, or points of interest • Database of worldwide geographic information • Generated using OSM data • “R “Reverse G Geocoding” service di ” i • Using the internet connection
  • 60. Finally, label the image • Geotag in standard EXIF f format • Read by most photo applications • (XMP sidecar for RAW images) • Latitude and Longitude • Address label & tags
  • 61. The end of our journey
  • 62. So, Where was I? • GPS is fantastic! • Assistance from a service is a Good Thing • it improves performance • and allows t t ll diff d ll totally different thi t things • You can Capture the signal, and Process it later • instant convenient operation instant, • very long battery life • Then you can do all sorts of things with the location • Identify, remember, label, find, sort, share, discover… and plot on a map! • It’s not “GPS” = “navigation” • E Everything can be aware of where it is (or was) – even photographs… thi b f h i ( ) h t h
  • 63. Thank you! locate, communicate, accelerate