Lecture 1 May 3rd 2006 Wednesday: 16:00-17:30 Rocco Malservisi: e-mail...

Lecture 1 May 3rd 2006

Wednesday: 16:00-17:30

Rocco Malservisi: e-mail [email protected] 21804202

Class Web page: www.geophysik.lmu.de/~malservisi/TectGPS.html

mailto:[email protected]


“Geodesy is the branch of applied

mathematics concerned with the

determination of the size and shape of

the Earth, with the exact positions of

points on its surface, and with the

description of variations of its gravity

field.”International Association of Geodesy definition

From Greek: “ DIVIDING THE EARTH ”`


How big is the Earth?

Which is the shapeof the planet?

How tall is a mountain?

Where my property ends? How big is my property?

Where am I?

How far am I from a place?

In which direction should I go?


If we want to have a mathematical representation of a point (point’s coordinate) we need to have a reference surface we can refer to.

Knowing the shape of the Earth we can define this surface.

The gravity field gives the best representation of the shape of the Earth.


The Earth is “almost” a sphere with a circumference ~40000 km longThe meter was defined using this length.


Eratosthenes (215 BC)

R~ 6267 km

S=4400 stadia ~787kmC=39376km


XVII XVIII Century Discussion of Oblate-Prolate spheroid

Cassini meridian south of France shorter than in ParisPROLATE

British Pendulum slower at equator and Newton equationsOBLATE

XVIII Century (1730) Expedition of France Academy:Peru measurement: 6376.45 km (Equatorial Radius)Lapland measurement: 6355.88 km (Polar Radius)OBLATE!!Difference: 1350m in 111km!!!


The Earth is “almost” a sphere with a circumference ~40000 km longThe meter was defined using this length.

Better approximate by an oblate ellipsoid

Today accepted Value Equatorial Radius 6378 kmPolar Radius 6357 kmSphere of Equal Volume Radius 6371 kmFlattening 1/298.257223563


The “real” shape of the planet is approximated by the Geoid:THE EQUIPOTENTIAL SURFACE AT THE MEAN SEA LEVEL

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.


We can divide geodesy

Space Geodesyuse of extra-terrestrialobject as observable.

Terrestrial GeodesyUse of terrestrial toolsAnd observable

Global GeodesyDetermination of shape of the Earth, global references.Geodetic SurveyDetermination of positions,and references over a regionfor which the Earth’s curva-ture can have influences.Plane SurveyDetermination of positions and references on a local level.

According to method

OR

According to what we observe


TRADITIONAL SURVEY

Horizontal positioning Vertical positioning

TRIANGULATION

TRILATERATION

TRAVERSING

ASTRONOMICALPOSITIONING

GEODETIC LEVELING

TRIGONOMETRIC HEIGHTING

BAROMETRIC LEVELING

TILTING


TRADITIONAL SURVEY

Horizontal positioning

TRIANGULATION


TRADITIONAL SURVEY


TRILATERATION


TRADITIONAL SURVEY


TRAVERSE

EDM


TRADITIONAL SURVEY

Vertical positioning

GEODETIC LEVELING

TRIGONOMETRIC HEIGHTING


SPACE SURVEY

VLBI Very Long Baseline Interferometry

SLR Satellite Laser Ranging

GPS Global Positioning System Glonass Galileo

DORIS

InSAR Interferometric Synthetic Aperture Radar


Very Long Baseline Interferometry

VLBI is a geometric technique: • It measures the time difference

between the arrival at two Earth-based antennas of a radio wavefront emitted by a distant quasar.

• Using large numbers of time difference measurements from many quasars observed with a global network of antennas, VLBI determines the inertial reference frame defined by the quasars and simultaneously the precise positions of the antennas.


SLR Satellite Laser Ranging

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture. QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.


The Global Positioning System• The Global Positioning System (GPS) is

a satellite-based navigation system.• GPS was originally intended for military applications, but in the

1980s, the government made the system available for civilian use.• GPS works in any weather conditions, anywhere in the world, 24

hours a day. There are no subscription fees or setup charges to use GPS

• Some civilian uses:– Navigation on land, sea, air

and space– Geophysics research– Guidance systems– Geodetic network densification– Hydrographic surveys

• The Global Positioning System (GPS) is a satellite-based navigation system.

• GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use.

• GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS

• Some civilian uses:– Navigation on land, sea, air

and space– Geophysics research– Guidance systems– Geodetic network densification– Hydrographic surveys


GlonassGlonass GLObal NAvigation Satellite System

Glonass is a Soviet space-based navigation system comparable

to the American GPS system.

The operational system contains 21 satellites in 3 orbital planes,

with 3 on-orbit spares.

Glonass provides 100 meters accuracy with its C/A

(deliberately degraded) signals and 10-20 meter accuracy with

its P (military) signals.

http://samadhi.jpl.nasa.gov/msl/Programs/gps.html


Doppler Orbitography and Radio positioning Integrated by Satellite

Precise orbit determination and location system using Doppler shift measurement techniques. A global network of 52 Doris orbitography beacons has been deployed. Doris was developed by Cnes, the French space agency, and is operated by CLS.

DORIS


• Two or more data acquisition of the same area from nearby location (< 1000 m)

• Enables detection of surface changes within cm level accuracy

InSAR

Lecture 1 May 3rd 2006 Wednesday: 16:00-17:30 Rocco Malservisi: e-mail...

Documents

Transcript of Lecture 1 May 3rd 2006 Wednesday: 16:00-17:30 Rocco Malservisi: e-mail...