Transcript Lecture09 - UCSB Geography

Mobile and Distributed GIS and
LBS
Geog 176B Lecture 9
The network is the computer
Computer
Network
Software
Localizer
Wired Networks
• “Last Mile to the house”
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300 baud dial-up early ‘80s
56 kbps dial-up (since mid 1990s)
ISDN 64-128 kbps (digital)
DSL: 1.5Mb down/64Kb up (6Mb/640K in future)
cable modem: 2 Mbps (load dependent)
• LANs (local area network) within building or campus
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300 baud RS232 (1970s)
10MB Ethernet (1980s)
100MB Ethernet (mid 1990s)
1GB Ethernet (late 1990s)
• WANs (wide area network) connects LANs
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shared, public facilities (Internet)
Dedicated Telco leased lines (fixed bandwidth)
• T1 (24 x 64 Kbps channels: 1.54MBps)
• T3 (28 T1 circuits: 45MBps; requires fiber)
Dedicated fiber (usually SONET protocol)
• OC1 (base rate) 50 mbps
OC12 = 600 Mbps
• OC3 = 150 Mbps
OC48 = 2.4Gbps
‘virtual circuit’ protocols (max. guaranteed bandwidth)
More “wires”
Twisted pair wire: (now up to 1Gbps)
distance/speed trade-off
150m. max. for highest speed
high speed: closet to desktop
(using Level 5 cable)
low speed: home to Telco office
Maximum leased line over copper is T1 (1.4Mbps)
Coaxial cable (up to 200Mbps):
longer distances (up to 20 miles)
was fading but cable TV and Internet brought revival for “last mile”
applications
Fiber optic (exceeds 100Gbps & doubling every 9
months--twice Moore’s Law)
single mode for distances over 1 or 2 miles
Multi mode within buildings
Wireless
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infrared (1 mile)
microwave (35 miles line of site)
satellite geostationary (22,000 miles up)--’group’ links
satellite low orbit --individual links
radio--mobile data networks (police)
Wireless LANs
(WiFi 802.11b/g)
• Cellular data: 3G services
• Satellite telephone link
Closer to
the Wire
Types of Protocols
• WAN transmission protocols:
– T1/T3 (old faithful for copper/fiber dedicated lines)
– SONET(Synchronous Optical Network)
– Virtual circuits: Frame Relay, SMDS (Switched Mutimegabit Data Service),
ATM (Asynchronous Transfer Mode) All are fading!
• LAN Transmission Protocols:
– Ethernet 10MB/100MB/1GB (the standard) (IEEE 802.3)
– Wireless: replaces wires over short distances
• 802.11b (WiFi): 11Mbps on 2.4GHz band (crowded spectrum)-300 feet coverage
• 802.11g: faster (54 Mbps) version of 802.11a
• Bluetooth: small, cheap (eventually) but doesn’t run tcp/ip
• Data Communication Protocols
– tcp/ip (transmission control program/internet protocol) the standard
– Tcp/ip has replaced
• WAN: SNA( old IBM proprietary), X.25 (old open)
• LAN: XNS (Xerox), IPX (Novell), Ethertalk(Apple), NetBIOS
Closer to – Internet: interconnected LANs and WANs running tcp/ip
the User – Internet2/NGI: Next Generation Internet univ/vendor coop. research
Bluetooth GPS
Example: AT&T at UCSB
Characteristics of Circuits and Networks
• circuit switched v. packet switched
– end-to-end connection established (e.g voice call)
– or, electronic packet traverses the network (like parcel via UPS)
• typology: star, hierarchy, bus, ring
• baseband v. broadband
– one service/channel/protocol per cable v. Multiple (e.g. cable TV is broadband)
• switched v. dedicated lines
– compete for circuit when needed
– or, have your own all the time
• public v. private
– share with all others (e.g. Internet)
– or, have your own (e.g. Intranet)
Networked GIS
• Configured within an organization or lab
• Collaboration across organizations
• Tools relatively undeveloped “Virtual
Organization” original vision of web
• Web portals offer GIS “services”
• Wireless access can be “on-the-spot”
• New industry-LBS
Ubiquitous Computing
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Computing any time, anywhere
Always on, trackers
Monitoring activity
Sensor networks
Localizers, Actuators
The GRID
Sensitive to multiple inputs
Emergence of LBS
• Convergent
technologies
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Cell phone
GPS
GIS
Wireless networking
• Impact has been on the
“where” of computing
For highly mobile GIS
GPS is critical
Wearable computing
http://www.itmedia.co.jp/broadband/0309/18
Vehicle navigation and tracking
Time-space Geography
Source: Jonathan Raper,
City University, London
A new role for GIS: highly
integrated spatial problem solving
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Need a theory of human mobility and access
Need real time multi-source data fusion
GIS continues to play the major role
Tools for 4D GIS only now getting started
Major constraint remains the human
computer interface
What is GPS?
• GPS is a Satellite-based Navigation System
• Generic term: Location Determination
Technology
• Funded by and controlled by the U. S.
Department of Defense (DOD). Originally
NAVSTAR
• Designed for military tasks: Dual Use
• Civil uses now far exceed military
One of three such systems
• GLONASS
• Galileo
• GPS Blocks I and II
– Block III and beyond
– Many new LDTs, some using GPS
– Pseudolites
The GPS System has the
following components
• Space Segment
• Ground/Control Segment
• User segment
What the Satellite Does
Radio signal transmission
Onboard atomic clock
Metadata in ephemeris
Carrier signal
The constellation
24 satellites
6 orbital tracks
4 satellites/track
12 hour orbits
Control Segment
• The Control Segment consists of a system of tracking stations located
around the world.
• GPS Master Control and Monitor Network located at Schriever Air
Force Base in Colorado
• These monitor stations measure signals from the
SVs which are incorporated into orbital models for each satellite
• The models compute precise orbital data (ephemeris) and SV clock
corrections for each satellite
• The Master Control station uploads ephemeris and clock data to the SVs
as they pass over
• The SVs then send subsets of the orbital ephemeris data to GPS
receivers over radio signals
The User Segment: The Signal
• Signals Specified In The Federal Radionavigation
Plan
• PPS: Precise Positioning Service
– Military/encrypted
– 22 m hor. 27.7 m vert. 200 ns accuracy
• SPS: Standard Positioning Service
– Civil users
– Subject to SA, but turned off May 1st, 2000
– 100m hor. 156m vert. 340 ns accuracy
GPS Satellite Signals
• The SVs transmit two microwave carrier signals.
• The L1 frequency (1575.42 MHz) carries the
navigation message and the SPS code signals.
• The L2 frequency (1227.60 MHz) is used to
measure the ionospheric delay by PPS equipped
receivers.
• Can process carrier phase delay for extra accuracy
Digital signal processing
• Three binary clock-tied codes shift the L1
and/or L2 carrier phase.
– The C/A code
– The P-code
– The Y-code
• Plus the navigation message
Received
Signal
In GPS
distance (m) = time (s) * c (m s-1)
4+ distance, three unknowns
Dilution of Precision
Ionospheric Effect
GDOP-PDOP
Pts w/ No Diff Correction
Pts w/ Diff Correction
Adeline Dougherty’s 176A project
Lots of multipath error!
Multi-path Error
WAAS network
• ~25 precisely
measured WRS (Wide
Area Reference
Stations)
• Receive signal from
GPS satellites, check
for error, then
broadcast the
correction
Accuracy
Usually about, 4-8m
With correction (WAAS), 1-3m
$150-300 gets you a new GPS
Garmin Quest $599
WAAS
Casio Protrek GPS Watch
Garmin Forerunner 201
$100-150
Garmin eTrex Vista
$60-150
Magellan Meridian
Gold GPS $250
WAAS
Precision Agriculture
GPS enabled innovation
Smart dust
MEMS and WINS
• Microelectromechanical systems
• Using semiconductor manufacturing techniques to
make analog devices
• Also called localizers
• Wireless Integrated Network Sensors (WINS)
provide distributed network and Internet access to
sensors, controls, and processors that are deeply
embedded in equipment, facilities, and the
environment.
Smart Dust Applications: Sensor webs
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Personal location
Object location (geosensors)
Autonomous bots (geoprobes)
Inventory control
Localized intelligence for IVHS
Machine control
Infrastructure inspection
Smart homes
Biosensors
Agrisensors!