presented by rehana jamal (gis expert & geographer) dated: 18.11.14 advance applications of...

Presented by

Rehana Jamal

(GIS Expert & Geographer)

Dated: 18.11.14

Advance Applications of RS/GIS in Geo-Environmental Conservation

Subject

Lecture-6 M.Phil & P.hd

Topic

Original GPS Technologies

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Russian: GLONASS(Global Navigation Satellite system) available to civilian in 2007

European Community: Galilio Positioning System

Chinese: Compass Navigation System

Indian: Indian Regional Navigation Satellite System

United States: NAVSTAR(Navigation Signal Time and Ranging) Global Positioning System

Advance GPS Technologies

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Advance GPS Technologies

Definition“A system of satellites, computers, and receivers that is able to determine the latitude and longitude and altitude of a receiver on Earth by calculating the time difference for signals from different satellites to reach the receiver.”

NAVSTAR Global Positioning System

Global Positioning System (GPS) is a DoD developed, worldwide, satellite-based radio navigation system .

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GPS project

was worldwide, satellite-based radio navigation system

was developed in 1973

was created by the U.S. Department of Defense (DoD)

run with 24 satellites

became fully operational in 1995

NAVSTAR Global Positioning System

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Orbital inclinationPolar Orbit 80-90°Sunsyncronous Orbit 55°Geostationary Orbit 0°

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Polar Orbit 80-90°Sunsyncronous Orbit 55°/60°Geostationary Orbit 0°

Orbital inclination

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Polar Orbit 80-90°

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Sunsyncronous Orbit 55°/60°

Geostationary/Geosynchronous orbit 0°

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Geostationary Orbit 0° Side view

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GPS is a Constellation of satellites

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Old Orbits 3 Orbits & 8 Satellites

New Orbits 6 Orbits & 4 Satellites

Satellite Distances of New Orbits

105°

30°

120°

105°

Satellites orbit

The constellation of GPS consists of 24 operational satellites. The U.S. Air Force Space Command (AFSC) formally declared the GPS satellite constellation as having met the requirement for Full Operational Capability (FOC) as of July 27, 1995.

GPS capabilities

Two service levels of GPS

1. SPS

2. PP S

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1. SPS(Standard Positioning Service)

2. PPS (Precise Positioning Service )

Provided on GPS L1 Frequency having C/A codeHorizontal accuracy = 100meters(95%)Vertical accuracy = 156meters (95%)Time transfer accuracy = 340 nanoseconds (95%)

Provided on GPS L1 & L2 Frequencies, both having P -code Horizontal accuracy = 22meters(95%)Vertical accuracy = 27.7meters (95%)Time transfer accuracy = 200 nanoseconds (95%)

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Figure:GPS signal structure

The satellites transmit on two L-band frequencies: L1 = 1575.42 MHz and L2 = 1227.6 MHz. Three pseudo-random noise (PRN) ranging codes are in use.

•The coarse/acquisition (C/A) code has a 1.023 MHz chip rate, a period of 1 millisecond (ms) and is used primarily to acquire the P-code. •The precision (P) code has a 10.23 MHz rate, a period of 7 days and is the principal navigation ranging code. •The Y-code is used in place of the P-code whenever the anti-spoofing (A-S) mode of operation is activated.

Original Design of GPS signals /GPS signal characteristics

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Selective Availability

A protection technique employed by the DOD to deny full system accuracy to unauthorized users.

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A Selective Availability Anti-spoofing Module (SAASM) is used by military Global Positioning System receivers to allow decryption of precision GPS coordinates, while the accuracy of civilian GPS receivers may be reduced by the United States military through Selective Availability.

This is a plot of GPS navigational errors through the SA transition prepared by Rob Conley of Overlook Systems for the GPS Support Center in Colorado Springs, Colorado. The GPS errors can be seen diminishing significantly around 0405 UTC (shortly after midnight EDT). The data indicates a circular error of only 2.8 meters and a spherical error of 4.6 meters during the first few hours of SA-free operation. The data was measured using a Trimble SV6 receiver.

Selective Availability (SA) was an intentional degradation of public GPS signals implemented for national security reasons.

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GPS Structure/GPS Segments

The SPACE segment consists of

24 operational satellites in six orbital planes (four satellites in each plane).

Orbits circular: 20,200 km (10,900 nm)

Inclination angle of 55 degrees

Period :12-hour

The position same at the same sidereal time each day

SPACE segment

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CONTROL segmentThe CONTROL segment consists of Five Monitor Stations (Hawaii, Kwajalein, Ascension Island, Diego Garcia, Colorado Springs)Three Ground Antennas, (Ascension Island, Diego Garcia, Kwajalein)Master Control Station (MCS) located at Schriever AFB in Colorado.

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The USER segment consists of Antennas and receiver-processors that provide positioning, velocity, and precise timing to the user.

USER segment

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GPS system time

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GPS system time is the atomic time scale implemented by the atomic clocks/Composite Clock (CC) in the GPS ground control stations and GPS satellites themselves GPS time was at 0h on 6 Jan,1980 and since it is not perturbed by leap seconds. The CC or "paper" clock consists of all operational Monitor Station and satellite frequency standards.

Semi-major axis

a Defines the size of the orbit.

Eccentricity e Defines the shape of the orbit.

Inclination i Defines the orientation of the orbit with respect to the Earth's equator.

Argument of Perigee

Defines where the low point, perigee, of the orbit is with respect to the Earth's surface.

Right Ascension of

the Ascending Node

Defines the location of the ascending and descending orbit locations with respect to the Earth's equatorial plane.

True/Mean Anomaly

Defines where the satellite is within the orbit with respect to perigee.

Orbital Elements Orbital elements are the parameters required to uniquely identify a specific orbit and are used to describe the motion of satellites within an orbit.

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Fig. A scale diagram showing earth and various orbits above it18 Nov-14 28

GPS Block IIIA

Lecture to be continued ………till Advance GPS Satellites

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Early Delta Flights

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“GPS is a system of satellites, computers, and receivers that provides 3 dimensional data.

developed in 1973 by the U.S. Department of Defense (DoD)

Old Orbits------3 Orbits & 8 Satellites

New Orbits--------6 Orbits & 4 Satellites

GPS capabilities

Satellite Distances of New Orbits

GPS Structure/GPS Segments

Design of GPS signals /GPS signal characteristics

Selective Availability

Summary

References

http://tycho.usno.navy.mil/gpsinfo.html

http://www.wisegeek.com/how-many-satellites-are-orbiting-the-earth.htm

http://www.gma.org/surfing/satellites/orbit.html

http://www.ehow.com/how-does_4900025_satellite-stay-orbit.html

http://spaceflight.nasa.gov/realdata/elements/index.html

http://marine.rutgers.edu/cool/education/class/paul/orbits2.html

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