What is GPS??

• Only system today able to show you your exact position on the Earth anytime, in any weather, anywhere.

• Network of satellites that continuously transmits coded information, which makes it possible to precisely identify locations on earth by measuring distance from the satellites

• First GPS satellite was launched in 1978

• It is constellation of 24 satellites with the solar panels extended powered by solar energy continuously broadcast coded radio signal

• The GPS satellites are uniformly distributed in a total of six orbits such that there are four satellites per orbit

Each satellite transmits low power radio signals on several frequencies

The three parts of GPS are:

• Satellites

• Receivers

• Software

(satellites)

(tracking stations)(receivers)

Satellite

• GPS satellites circle the earth twice a day in very precise orbit and transmit information to earth.

• GPS units are made to communicate with GPS satellites (which have a much better view of the Earth) to find out exactly where they are on the global scale of things.

Receivers • Receiver take all information and use Triangulation

to calculate the users exact location

• Now, receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is.

• With distance measurement from a few more satellite,the receiver can find the users position and display it on the unit electronics map.

How GPS Works…

1 Distance fromsatellites needsto be known

4 Correct for atmosphericand ionospheric errors

3 Need to knowSatellite position

2 Accurate(Atomic)Clocks arerequired

Calculating Distance

Velocity x Time = DistanceRadio waves travel at the speed of light, roughly

186,000 miles per second (mps)

If it took 0.06 seconds to receive a signal transmitted by a satellite floating directly overhead, use this formula to

find your distance from the satellite.

186,000 mps x 0.06 seconds = 11,160 miles

Pocket PC

• A Pocket PC, abbreviated P/PC or PPC, is a hardware specification for a handheld-sized computer (Personal Digital Assistant) that runs the Microsoft Mobile Operating system.

• It may have the capability to run an alternative operating system like NetBSD , Linux , Android or others. It has many of the capabilities of modern desktop PCs.

• The Pocket PC includes Excel, Word, Microsoft Reader, Windows Media Player, File Explorer, Internet Explorer, Calendar, Contacts, Tasks, and Notes (voice, text and ink).

• Microsoft compliant Pocket PCs can also be used with many other add-ons like GPS receiver , barcode readers,RFID readers, and cameras.

• Devices without an integrated phone are called Windows Mobile Classic instead of Pocket PC. Devices with an integrated phone and a touch screen are called Windows Mobile Professional.

For instance, any device which is to be classified as a Pocket PC must

• Run Microsoft's Windows Mobile, PocketPC edition

• Come bundled with a specific suite of applications in ROM

• Include a touchscreen. • Include a directional pad or touchpad• Include a set of hardware application buttons • Be based on an ARM version 4 compatible CPU,

Intel Xscale CPU, MIPS CPU or SH3 CPU.

OS versions

• Windows Mobile 6.1• Windows Mobile 6.1• Windows Mobile 5• Windows Mobile 2003• Pocket PC 2000 and 2002

Pocket PC with GPS system

• Normally a Pocket PC has space upto 100 MB,to increase its storage capacity we add storage cards which increase its space upto 6 GB

• To install GPS in Pocket PC we required:- Hardware,which communicate with satellite Software,which display required information

Hardware for Pocket PC

• Notebooks (Web Server + ArcIMS)

ArcIMS-it is a GIS that is designed to serve maps across the internet

• Pocket PC (Clients + Wi-Fi compact flash card)

• Wireless Access Point (Hub)+ Twisted Ethernet Cable (directly from Server to Hub)

Software for Pocket PC

• TomTom Navigator 3 for PocketPC SmartPhone and Palm Tungsten T3

• Powerloc Destinator 3, PocketMap Navigator, Rayming iGuide, Pharos Pocket GPS Navigator, Powerloc Destinator 3,SATNAV for pocket PC

• Route 66 from Route 66 Graphical Information Systems is for PocketPC.

Type of Software system

• Offline Software system no internet required information already store in fed software

• Online Software system internet connect required e.g:- Google map

• Need signal from at least four SVs for 3D position

• One SV provides a time reference

• Distance to three remaining SVs is determined by observing the GPS signal travel time from SV to the receiver

• With three known points, and distances to each, we can determine the GPS receiver’s position

TO GET A POSITION

Offline Software system• First hardware communicate with satellite (mium.

4 satellite required) and get information at a point where all 4 satellite signals intersect

• then,it send information to fed software,here software calculate point’s latitude and longitude,then compare its value with already stored value and finally display exact position

• I-Mate use SATNAV software

• Wireless Local Area Network (WLAN) IP address-based (130.191.118.30)

Wi-Fi• is the trade name for a popular wireless

technology used in home network,mobile phone, video games and more.

• The purpose of Wi-Fi is to hide complexity by enabling wireless access to applications and data, media and streams. The main aims of Wi-Fi are to:

ensure compatibility and coexistence eliminate cabling and wiring eliminate switches, adapters, plugs and

connectors.

Online Software system • For this purpose there has to a internet connection

• E.g:- Google map

• that take information through GPRS(General Packet Radio Service) then send it to GPS to display

Internet Map Server on notebook computer with wireless access port.

Field workers: Pocket PC, GPS, and wireless card.

Wi-Fi wireless communication (up to 300 feet)

Research Agenda

• Enhance Information Security – Wireless

Communication. (for sensitive data) PDA:

Fingerprint ID.

• Data Transmission Efficiency (compression

techniques)

• User Interface Design (Different from Desktop PC)

• Smart Display for different devices (Software

Agents)

Current Limitations and Problems

• Wireless Technology is changing fast.

• The short range of current commercial devices

(300 – 1000 feet)

• Limited Software Customization Capability (only

user interface customization, no system function

level, such as direct data upload)

• Pocket Internet Explorer (No Java applets

capability)

Sources Of Errors• Atmospheric Delay

• Single Multipath

• Receiver Clock Error

• Orbital Error

• Satellite Geometry/Shading

Atmospheric Delay

• The satellite signal slows as it passes through the atmosphere.

• The GPS system uses a built in model that calculate an average amount of delay to partially correct for this type of error

Multipath means that the same radio signal is received several times through different paths. For instance, a radio wave could leave a satellite and travel directly to the receiver, but it also bounces off a building and arrives at the receiver at a later time.

Multipath Errors

The internal satellite and receiver clocks have limited accuracy, and they are not precisely synchronized. Since position computations are highly dependent on accurate timing information, small clock errors can cause significant errors in position computations.

Clock Limitations

Ephemeris Error (Orbital errors)

Inaccuracies in reported position of satellite

Satellite Geometry/Shading

This refer to the relative position of the satellite at any given time.Ideal satellite geometry exists when the satellite are located at wide angle relatives to each other.Poor geometry results when the satellite are located in a line or in a tight grouping

How accurate is GPS

Depend on some variables• Time spent on measurement

• Design of receiver

• Relative position of satellite

• Use of Differential Techniques

Application

Military• GPS allows accuracy

targeting of various military weapons including ICBMs,missiles etc

• Used to navigate and coordinate the movement of troops and supplies

• GPS receivers have been minimized to just a few integrated circuits and so are becoming very economical.

• These days GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers.

Bibliography

• Http://map.sdsu.edu/mobilegis

• Google.com

• The Gps Handbook: A Guide for the Outdoors by Robert I. Egbert, Joseph E. King