Geodesy and Surveying: Reference Systems and Joint Evaluation

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Questions and Answers

What is the recommended approach for evaluating GPS data records in a terrestrially specified datum?

Elimination of GPS data by additional parameters

Joint evaluation of GPS and terrestrial measurements without additional parameters

Transformation of GPS data into the available coordinate system and joint equalisation of GPS and terrestrial measurements (correct)

Separate evaluation of GPS and terrestrial measurements

What is the primary function of a geodetic reference system?

To establish a local land survey

To provide a physical definition of a point in space

To determine the spatial position, location, height, or gravity of points (correct)

To define the position coordinates, heights, and gravity values of points

What are the three types of geodetic reference systems?

Ellipsoid, geoid, and topographic reference systems

Position, height, and gravity reference systems (correct)

Local, national, and global reference systems

Terrestrial, GPS, and satellite reference systems

What is the primary purpose of combining GPS and terrestrial measurements in land surveying?

To eliminate disturbing influences of the subsoil and object Signup and view all the answers

What is the purpose of transforming GPS data into the available coordinate system?

To enable joint evaluation of GPS and terrestrial measurements Signup and view all the answers

What is the reference system used for GPS coordinates?

WGS84 Signup and view all the answers

What is the result of jointly processing GPS and terrestrial measurements?

A combined set of GPS and terrestrial coordinates Signup and view all the answers

What is a geodetic reference system physically defined by?

Position coordinates, heights, and gravity values Signup and view all the answers

What is the dimensionality of GPS measurements?

Three-dimensional Signup and view all the answers

What is the purpose of creating a joint model for terrestrial and satellite-based observations?

To combine the advantages of both methods Signup and view all the answers

What is the purpose of a geodetic reference system?

To define the spatial position, location, height, or gravity of points Signup and view all the answers

What is the role of additional parameters in the joint evaluation of GPS and terrestrial measurements?

To eliminate the date-determining part of GPS data Signup and view all the answers

What is the reference surface used for height measurements?

Geoid Signup and view all the answers

What is the purpose of using GPS points as a frame around the terrestrial network?

To control network points close to objects Signup and view all the answers

Why are calculation algorithms necessary when combining GPS and terrestrial measurements?

Because of the different reference systems Signup and view all the answers

What is the benefit of using three-dimensional measurements and analyses in engineering surveying tasks?

Enhanced monitoring capabilities Signup and view all the answers

What is the purpose of leveling geodetic instruments with spirit levels and compensators?

To align the vertical axes in the direction of gravity Signup and view all the answers

What is the geoid?

A level surface that best approximates the actual undisturbed sea surface Signup and view all the answers

What is the purpose of geodetic measurements?

To map the coordinates of points in a defined mathematical coordinate system Signup and view all the answers

What is a levelling area?

The surface of the world's oceans at rest Signup and view all the answers

What is the relationship between the geoid and the ocean surface?

The geoid is equivalent to the ocean surface at rest Signup and view all the answers

What is the purpose of reference systems?

To determine the coordinates of points on the Earth's surface Signup and view all the answers

What is the equilibrium surface that is perpendicular to the direction of gravity at any point?

The geoid Signup and view all the answers

What is the result of levelling geodetic instruments?

The vertical axes are aligned in the direction of gravity Signup and view all the answers

Study Notes

Basic Networks: Joint Evaluation of GPS and Terrestrial Measurements

GPS measurements are used to determine points in land surveying, and can be combined with terrestrial measurements to create and consolidate 3D engineering networks.
Control of network points close to objects (e.g. dams, landslide slopes) is achieved by connecting them to GPS points, which provides a frame around the terrestrial network or its extension in the rearward direction.
Disturbing influences of the subsoil and object (e.g. dead weight, water pressure) can be eliminated as far as possible by combining GPS observations with terrestrial measurements.

Reference Systems

GPS coordinates are referenced to the geocentric WGS84, while country coordinates are referenced to a reference ellipsoid.
GPS coordinates are three-dimensional, and three-dimensional measurements and analyses are increasingly being used for engineering surveying tasks.
The coordinate reference is the ellipsoid, and the height reference surface is the geoid.
A joint model is recommended to equalize terrestrial and satellite-based observations.

Evaluating GPS Data

GPS data is evaluated in a terrestrially specified datum by transforming the GPS data into the available coordinate system (national network or local construction site or monitoring network).
The joint equalization of GPS and terrestrial measurements is performed, eliminating the date-determining part by additional parameters (translations, rotations, scale).

Geodetic Reference System

A geodetic reference system is a basic determination system for defining the spatial position, location, height, or gravity of points.
A reference system consists of a coordinate system and a fixed point field.
There are three types of geodetic reference systems: position reference system, height reference system, and gravity reference system.

Reference Surfaces

Geodetic instruments are levelled with spirit levels and compensators to align the vertical axes in the direction of gravity.
The level surface (equipotential surface) is an infinite number of surfaces perpendicular to gravity.
The geodetic measurements refer to a specific level surface, known as the geoid.
The geoid is a level surface that best approximates the actual undisturbed sea surface, imagined to continue under the continents.
The geoid is represented by the ocean surface at rest, unaffected by tides and continuing beneath the continents.

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Description

Learn about the integration of GPS and terrestrial observations in geodesy and surveying, and how they are joined to produce accurate results. Understand the basics of reference systems and their importance in geodesy.