nice presentation on gps, geotagging and its future

locate, communicate, accelerate

Now where was I?Now, where was I?

Dr Chris Marshall chris.marshall@u-blox.comchris.marshall@u blox.comNovember 2010IET Buckinghamshire region

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

Imaging and the WebImaging and the Web

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

Need to add extra data to photos

Time

Location

Subject

LondonLondonEye

© u-blox AGSlide 5

Applications/Websites ready for geotagged images

iPhoto 09

PicasaWeb

Flickr

© u-blox AGSlide 6

locate, communicate, accelerate

The Global Positioning System

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)

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

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

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

Measuring Propagation Time

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

sentsent

τ

received

time

Measuring Propagation Time

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

sentsent

τ

received

sent

time

Measuring Propagation Time

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

sentsent

received

replica

time

Measuring Propagation Time

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

sentsent

received

replica

time

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

sentsent

received

replica

timetime

Measuring Propagation Time

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

sentsent

received

replica

τ

timetime

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)

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

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

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”.

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

Assisted GPSAssisted GPS

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

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

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

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

Software GPS and Capture and Process technology

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

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

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

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

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

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

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

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

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

Doing things with Capture and Process GPS

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

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

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

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

Taking the students to university

• Crossing Europe

• 5 days

• Captures every 2.5min

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

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

Taking the students to university

• Boarding the ferry dat Rotterdam

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

We’re all going on a summer holiday…

• For 2 weeks

• Sailing around Fynn, Denmark

• Samples every 3min

© u-blox AGSlide 53

locate, communicate, accelerate

51º14.51’N, 000º12.29’WhWhat next?

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

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

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

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

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

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

The end of our journeyThe end of our journey

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…

Thank you!

locate, communicate, accelerate