nice presentation on gps, geotagging and its future

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locate, communicate, accelerate Now where was I? Now, where was I? Dr Chris Marshall chris.marshall@u-blox.com chris.marshall@u blox.com November 2010 IET Buckinghamshire region

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Page 1: Nice presentation on GPS, Geotagging and its Future

locate, communicate, accelerate

Now where was I?Now, where was I?

Dr Chris Marshall [email protected]@u blox.comNovember 2010IET Buckinghamshire region

Page 2: Nice presentation on GPS, Geotagging and its Future

Where we will go…g

• Your many photos

• GPS• Assisted GPS

C t d P l t t h l• Capture and Process later technology• and what we can do with it

• Useful information out of location• Useful information out of location

Page 3: Nice presentation on GPS, Geotagging and its Future

Imaging and the WebImaging and the Web

Page 4: Nice presentation on GPS, Geotagging and its Future

Large photo collections lead to challenges

??

Where is the photo I want?

Where was this photo taken?

How do I get more from my photos?

How can I share the story?Where was this photo taken?

© u-blox AGSlide 4

Page 5: Nice presentation on GPS, Geotagging and its Future

Need to add extra data to photos

Time

Location

Subject

LondonLondonEye

© u-blox AGSlide 5

Page 6: Nice presentation on GPS, Geotagging and its Future

Applications/Websites ready for geotagged images

iPhoto 09

PicasaWeb

Flickr

© u-blox AGSlide 6

Page 7: Nice presentation on GPS, Geotagging and its Future

locate, communicate, accelerate

The Global Positioning System

Page 8: Nice presentation on GPS, Geotagging and its Future

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)

Page 9: Nice presentation on GPS, Geotagging and its Future

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

ARa ARa

BRb

Page 10: Nice presentation on GPS, Geotagging and its Future

To measure the distance from a satellite…

• Measure the time taken for a signal to l f h lli h itravel from the satellite to the receiver

• 3ns 1m

• Distance = time × c• Distance = time × c

Page 11: Nice presentation on GPS, Geotagging and its Future

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 i k hi h i l i f hi h t llit (CDMA)• So the receiver knows which signal is from which satellite (CDMA)

• The spreading code takes exactly 1ms to send and it is sent every ms• 1 023Mb/s1.023Mb/s

• Symbolically (the code is actually 1023 bits long):

sent

0mstime

1ms 2ms 3ms 4ms

Page 12: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

• The signal has a delay when it arrives at the receiver

sentsent

τ

received

time

Page 13: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

• The signal has a delay when it arrives at the receiver

sentsent

τ

received

sent

time

Page 14: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

• So the receiver scans all time offsets for the signal…

sentsent

received

replica

time

Page 15: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

• So the receiver scans all time offsets for the signal…

sentsent

received

replica

time

Page 16: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 17: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 18: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 19: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 20: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 21: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 22: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 23: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

sentsent

received

replica

timetime

Page 24: Nice presentation on GPS, Geotagging and its Future

Measuring Propagation Time

• To find the time where they match (“correlate”)

sentsent

received

replica

τ

timetime

Page 25: Nice presentation on GPS, Geotagging and its Future

In 3 D spaced 3 di• Need to measure 3 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)2Rc (X Xc) + (Y Yc) + (Z Zc)

Page 26: Nice presentation on GPS, Geotagging and its Future

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• An offset δt is caused by the discrepancy between our clock and “GPS time”

• In our 2D example:(Ra + c×δt)2 (X Xa)2 + (Y Ya)2 + (Z Za)2p(Ra + c×δt)2 = (X-Xa)2 + (Y-Ya)2 + (Z-Za)2

(Rb + c×δt)2 = (X-Xb)2 + (Y-Yb)2 + (Z-Zb)2

ARac.δt ARac.δt

BRb c.δt

BRb c.δt

Page 27: Nice presentation on GPS, Geotagging and its Future

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(Ra + c×δt) = (X Xa) + (Y Ya) + (Z Za)

(Rb + c×δt)2 = (X-Xb)2 + (Y-Yb)2 + (Z-Zb)2

2 2 2 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

Page 28: Nice presentation on GPS, Geotagging and its Future

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• The basic satellite signal is modulated with a 50 bits/s data message

• The message lasts 18s,d i t d 30and is repeated every 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 startthe “Time To First Fix”.

Page 29: Nice presentation on GPS, Geotagging and its Future

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

d• measured

• The satellites describe their orbits with a slow additional modulation of the signalwhich takes ~30s to receive

• GPS receivers requires measurements from 4 satellites to calculate their position in 3D space and GPS time

Page 30: Nice presentation on GPS, Geotagging and its Future

Assisted GPSAssisted GPS

Page 31: Nice presentation on GPS, Geotagging and its Future

GPS Signals are very weak

Earth radius

6,378 km

• 45W transmitter

• 20,180 km away, y

• 10 million times weaker than WiFi signals

© u-blox AGSlide 31

Page 32: Nice presentation on GPS, Geotagging and its Future

It can be difficult to download the data from the satellites

• You need a reasonable signal (-142dBm)f bl i ( )for reasonable time (>18s)

• to demodulate the data message

• to get ephemeris orbit information• to get ephemeris orbit information

• to calculate the satellites’ location

• This limits practical performance• Starting in urban canyons

• Using indoors• Using indoors

© u-blox AGSlide 32

Page 33: Nice presentation on GPS, Geotagging and its Future

Assisted GPS

• Ephemeris information gathered f ll lli ld idfrom all satellites, worldwide.

• Satellite orbit information provided on request to userprovided on request to userover communication channel

• Current ephemeris data: 1-3KBlid f 2 4 hvalid for 2-4 hours

ReceiverReceiver

ite it ase

cellular

Merge

Sat

ell

Orb

iD

atab

a

Internet Internet

Page 34: Nice presentation on GPS, Geotagging and its Future

Benefits of Assisted GPS

• Faster response• No need to wait 30s to download ephemeris information

from the GPS satellites

• Better coverage and availabilityBetter 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

Page 35: Nice presentation on GPS, Geotagging and its Future

Software GPS and Capture and Process technology

Page 36: Nice presentation on GPS, Geotagging and its Future

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 d i ill i i l t i d• Consumer devices will increasingly contain processors and memory• Able to share resources with other functions

• Continuing improvements from Moore’s lawContinuing improvements from Moore s law

• The most expensive part of GPS is the baseband processing chip

• To make everything position-aware, can we implement baseband y g p pprocessing in software?

• Standard software (C), processor platform, and memory

A ti it i d b bl i 2009• Activity acquired by u-blox in 2009

Page 37: Nice presentation on GPS, Geotagging and its Future

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• To demodulate data

• Plus high accuracy calculations• For position calculation 3%

AcquisitionMeasure

p6% 3%

91%

easu eFix

Page 38: Nice presentation on GPS, Geotagging and its Future

Conventional, hardware signal processor

• Baseband signal processing i.c., containing banks of correlators

• Real time signal processing• Signal processed, then discarded

R l ti t t f “ d ”• Real time output of “pseudo-ranges”

• Fix calculated live from the current pseudo-range values

Page 39: Nice presentation on GPS, Geotagging and its Future

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

Page 40: Nice presentation on GPS, Geotagging and its Future

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

Page 41: Nice presentation on GPS, Geotagging and its Future

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 PC processor and memory resources

• Access to internet and assistance services• Provides the satellite location information

Page 42: Nice presentation on GPS, Geotagging and its Future

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• Worldwide orbit information provided on request for the time when the GPS signal captured

Page 43: Nice presentation on GPS, Geotagging and its Future

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• 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

Page 44: Nice presentation on GPS, Geotagging and its Future

Key benefits of Capture & Process

• Instant capture of location data: No waitingNo change in user experienceg p

l i lif f h h• Very low power consumption: Battery life of months, not hoursVirtually no impact on battery life.

• Lowest cost• Lowest costOnly require a GPS radio, antenna and software

© u-blox AGSlide 44

Page 45: Nice presentation on GPS, Geotagging and its Future

Doing things with Capture and Process GPS

Page 46: Nice presentation on GPS, Geotagging and its Future

Adding to a camera

• Just add antenna and front end radio

• Captured GPS signal data stored with photo• Captured GPS signal data stored with photo

• Processed later when picture uploaded to PCPrototyping C17-C1 board

© u-blox AGSlide 46

Page 47: Nice presentation on GPS, Geotagging and its Future

Making a camera accessory

• Held and triggered by h h hthe camera hot shoe

• JOBO PhotoGPS• No waiting when taking a photo• No waiting when taking a photo

• No on-off switch

• No manual clock alignment needed (to synchronise the accessory and camera)

© u-blox AGSlide 47

Page 48: Nice presentation on GPS, Geotagging and its Future

Jobo photoGPS

• Accessory device• Captures 200ms GPS signal

• Stores up to 4000 geotags

• 120mAhour internal battery yrecharged by USB, lasts up to 4 weeks

• PC processing software C p ocess g so t a e• matches captures

with photos

• GPS position accuracy 10mGPS position accuracy 10m

• finds Reverse geocode

• places result in photo EXIF

• Distributor MINOX (GB) Ltd, Luton. www.minox.uk

© u-blox AGSlide 48

Page 49: Nice presentation on GPS, Geotagging and its Future

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 monthson just a 130mAhr battery

100000on just a 130mAhr battery

• Memory for storing Captures 1000

10000

s pe

r day

Battery emptyM f ll• Capture size typically 128KB

• 8Gb memory gives >8000 Captures 10

100

Cap

ture

s Memory full

g p

• Capacity for a 1 month sampling every 5 minutes

10 10 20 30 40 50 60 70 80 90 100

Days usage

Page 50: Nice presentation on GPS, Geotagging and its Future

Taking the students to university

• Crossing Europe

• 5 days

• Captures every 2.5min

Slide 50 Copyright © 2007: u-blox AG, 5 December 2010

Page 51: Nice presentation on GPS, Geotagging and its Future

Taking the students to university

• Driving around Belgium d h h l dand the Netherlands

Slide 51 Copyright © 2007: u-blox AG, 5 December 2010

Page 52: Nice presentation on GPS, Geotagging and its Future

Taking the students to university

• Boarding the ferry dat Rotterdam

Slide 52 Copyright © 2007: u-blox AG, 5 December 2010

Page 53: Nice presentation on GPS, Geotagging and its Future

We’re all going on a summer holiday…

• For 2 weeks

• Sailing around Fynn, Denmark

• Samples every 3min

© u-blox AGSlide 53

Page 54: Nice presentation on GPS, Geotagging and its Future

locate, communicate, accelerate

51º14.51’N, 000º12.29’WhWhat next?

Page 55: Nice presentation on GPS, Geotagging and its Future

Maps used to be expensive

• Nokia acquired Navteq, for $8.1bn i i f h i hnavigation now free on their phones

• except that you have to pay for the data traffic for the mapsp

• TomTom acquired TeleAtlas for $4.3bn

f i h h i i i d i• for use with their navigation devices

• Google provides maps for free• except that you look at their• except that you look at their

advertising

Ordanance SurveyNational Library of Scotland

© u-blox AGSlide 55

National Library of Scotland

Page 56: Nice presentation on GPS, Geotagging and its Future

Open Street Map

• A map for all, by all

• Hosted at UCLwww.openstreetmap.org

• Supported worldwide• Supported worldwide

• Lots of content• 321 114 contributing users321,114 contributing users

• Governments and organisationsalso making their data available

2 054 774 073 GPS i• 2,054,774,073 GPS points

• 829,249,405 nodes 69,300,449 ways

• Highlights at www.bestofosm.org

© u-blox AGSlide 56

Page 57: Nice presentation on GPS, Geotagging and its Future

Mapping of photos, good for routes and tripspp g p g p

Page 58: Nice presentation on GPS, Geotagging and its Future

Describe the location by “Reverse Geocoding”

• Converts lat long• Converts lat-long coordinates into:

• Road

• Nearest town

• Region

• Country

• Also add nearbyPoints Of Interest

© u-blox AGSlide 58

Page 59: Nice presentation on GPS, Geotagging and its Future

Location labelling service

• Labelling with address, or points of interest

• Database of worldwide geographic information• Generated using OSM data

“R G di ” i• “Reverse Geocoding” service

• Using the internet connection

Page 60: Nice presentation on GPS, Geotagging and its Future

Finally, label the image

• Geotag in standard fEXIF format

• Read by most photo applicationsapplications

• (XMP sidecar for RAW images)

• Latitude and Longitude

• Address label &• Address label & tags

Page 61: Nice presentation on GPS, Geotagging and its Future

The end of our journeyThe end of our journey

Page 62: Nice presentation on GPS, Geotagging and its Future

So, Where was I?

• GPS is fantastic!

• Assistance from a service is a Good Thing• it improves performance

d ll t t ll diff t thi• and allows totally different things

• You can Capture the signal, and Process it later• instant convenient operationinstant, convenient operation

• 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 thi b f h it i ( ) h t h• Everything can be aware of where it is (or was) – even photographs…

Page 63: Nice presentation on GPS, Geotagging and its Future

Thank you!

locate, communicate, accelerate