Historical Development of Satellite Positioning System (SPS)

Geodesy

is the science of measuring and mapping the Earth’s surface, including the determination of the Earth’s external gravity field.

Satellite geodesy

refers to the observational and computational techniques that use precise measurements to, from, or between artificial satellites to solve geodetic problems.

shape of the Earth, its gravity field, and the relationships between distant locations

From the beginning of the Space Age, scientists recognized that artificial satellites could be used to study the

J. A. O’Keefe;

“On the Utility of an Artificial Unmanned Earth Satellite,”;

intercontinental distances;

Earth’s gravity field

The first idea for using satellite geodesy was proposed by planetary scientist ___ in 1955. His proposal, ___ suggested using an inflated satellite illuminated by searchlights or radar. By tracking the satellite, scientists could potentially measure ___ and map the ___.

line of sight

raditional surveying methods such as triangulation, trilateration, traversing, and leveling were strongly limited by

about 100 m

Astronomic positions used to control classical surveying could have errors of up to

Satellite-based positioning

is the determination of the positions of observing sites on land, at sea, in the air, or in space using artificial satellites.

space program and military-funded research

Satellite-based positioning developed from the ___ intended to create a global navigation and guidance system.

Global Navigation Satellite Systems (GNSS)

Today, the overall group of satellite systems used for positioning is called

GNSS

provides positioning and timing information with high reliability and relatively low cost.

GNSS

t can operate day or night and in different weather conditions, and unlike conventional surveying, it does not require a direct line of sight between ground survey stations.

Distance = Travel Time × Signal Speed

Basic Principle of Satellite Positioning

Earth-to-space methods

occur when a satellite is observed using ground-based instruments.

Space-to-Earth methods

occur when a satellite carries an instrument or sensor in its payload to observe the Earth.

Space-to-space methods

occur when one satellite uses its instruments to track another satellite, or when satellites track one another.

1. determination of precise global, regional, and local three-dimensional positions
2. determination of the Earth’s gravity field and functions related to it
3. measurement and modeling of geodynamical phenomena

three major functions or problems addressed by satellite geodesy

engineering

for navigation, GPS, civil engineering, deformation monitoring, cadastral information, and GIS.

geophysics and geology

for mineral exploration, monitoring crustal and earthquake deformation, and studying plate tectonics.

oceanography and navigation

for studying sea-level rise, tides, ship routing, and hydrography.

geoinformatics

for spatial data gathering, manipulation, and retrieval.

geometrical method

also called the direct method, treats the satellite as a high target.

geometrical method

allows long geodetic distances to be established, such as connections between islands or continents.

dynamical method

also called the orbital or indirect method, treats the satellite as a sensor or probe in the Earth's gravity field.

dynamical method

satellite's orbital motion and changes in its orbital parameters are observed to determine the forces acting on the satellite.

1. high-orbiting targets
2. probes or sensors in the Earth's gravity field

artificial satellites have two fundamental uses in geodesy

1. R is the position vector of the antenna relative to the origin
2. r is the position vector of the satellite relative to the origin.
3. ρ (rho) is the range vector between the antenna and the satellite.

In basic satellite point positioning, three important vectors are used.

SPUTNIK-1 on October 4, 1957

The proper development of satellite geodesy began with the launch of ___, the first artificial satellite to achieve Earth orbit.

f = 1/298.3

One of the early major discoveries was the confirmation of the Earth's flattening, with an approximate value of

:EXPLORER-1 and SPUTNIK-2

f = 1/298.3 This value was obtained from observations of ___

1955

J. A. O'Keefe proposed using an artificial satellite for geodetic purposes.

1957

SPUTNIK-1 was launched and became the first artificial satellite to achieve Earth orbit.

1958

Earth's flattening was determined from satellite observations as approximately f = 1/298.3.

1958

EXPLORER-1 was launched.

1959

The third zonal harmonic was identified, contributing to the understanding of the Earth's pear-shaped form.

1959

Brouwer developed the theory of the motion of artificial satellites.

1960

TRANSIT-1B was launched.

1960

ECHO-1 was launched.

1960

Kaula developed the theory of satellite orbits.

1962

ANNA-1B was launched.

1962

A geodetic connection between France and Algeria was established by IGN.

1964

major geodetic problems had been successfully addressed, including determining a precise value for Earth's flattening, determining the general shape of the global geoid, and establishing connections between important geodetic datums to approximately ±50 m.

Navy Navigation Satellite System (NNSS) or the TRANSIT system

The first generation of satellite positioning systems began in 1958 with the

Doppler principle

TRANSIT was based on the

Doppler shift

is the change in frequency of a signal caused by the relative motion between the satellite and receiver.

5 to 7 satellites;

1,100 km

The TRANSIT constellation generally consisted of ___ operating at an altitude of approximately ___ in polar orbits.

U.S. Navy Polaris submarine fleet

The original purpose of TRANSIT was to support the navigation of the

Doppler principle

is based on the apparent change in frequency of a signal caused by relative motion between the signal source and observer.

Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning System (GPS)

Because of the success of the Doppler program, the U.S. Department of Defense (DoD) began developing the

GPS

was developed as a global satellite-based positioning system, like TRANSIT, it relies on signals transmitted from satellites whose orbital positions are precisely determined.

December 8, 1993;

July 17, 1995

GPS became initially fully operational on ___, and achieved Full Operational Capability (FOC) on ___.

Cold War

Satellite positioning technology emerged during the

Phase 1: 1958–around 1970

Development of Basic Satellite Methods

Development of Basic Satellite Methods

This phase focused on developing basic methods for satellite observation, orbit computation, and orbit analysis.

Smithsonian Astrophysical Observatory Standard Earth Models (SAO SE I to SAO SE III) and the Goddard Earth Models (GEM)

Examples of early Earth models included the

PAGEOS (Passive Geodetic Satellite)

a metallic balloon or balloon satellite.

Phase 2: 1970–around 1980

Scientific Projects

Scientific Projects

This phase was characterized by the development and refinement of new observation techniques.

TRANSIT system

was used for geodetic Doppler positioning.

Phase 3: 1980–around 1990

Operational Use of Satellite Techniques

Operational Use of Satellite Techniques

During this phase, satellite techniques became increasingly operational in geodesy, geodynamics, and surveying.

Satellite techniques

almost completely replaced classical astrometric techniques for monitoring polar motion and Earth rotation.

Phase 4: 1990–around 2000

International and National Permanent Services

International and National Permanent Services

This phase saw the development of major international and national permanent satellite services.

International Earth Rotation Service (IERS)

was initiated in 1987 and uses space techniques to provide highly accurate Earth orientation parameters.

International Celestial Reference Frame (ICRF)

based on interferometric radio observations.

International Terrestrial Reference Frame (ITRF)

based on different space geodetic techniques.

International GPS Service (IGS)

began in 1994 and became an important source of precise GPS orbits, coordinates, and observations from a global network of more than 300 permanently observing reference stations.

Phase 5: 2000 Onwards

Continued Development of Satellite Geodesy

1. CHAMP
2. GRACE
3. GOCE

Important developments included the launch of dedicated gravity-field missions, such a