Coordinate Systems & Satellite Positioning: Introduction to Geodesy

This set of vocabulary flashcards covers the foundational concepts of geodesy, coordinate systems, and the specific Australian geospatial datums and reference frames discussed in Workshop 1.

Geodesy

The science of accurately measuring and understanding the Earth's geometric shape, orientation in space, and gravity field.

Coordinate Reference System (CRS)

A system that defines the parameters of the axes and units, with reference to the Coordinate Reference Frame (CRF), to enable the communication of coordinates for one point relative to another.

Coordinate Reference Frame (CRF)

The practical realisation of a Coordinate Reference System (CRS).

Cartesian Coordinate System

A coordinate system using $X$, $Y$, and $Z$ axes to define a position.

Geographic (Polar) Coordinate System

A coordinate system that defines position using Latitude ($\phi$), Longitude ($\lambda$), and Height.

Australian Geospatial Reference System (AGRS)

A collection of datums, reference frames, working surfaces, infrastructure (such as GNSS CORS), models, and standards used to define latitude, longitude, and height throughout Australia.

Static Datum

A spatial reference system held fixed at a specific point in time, known as a reference epoch, and considered as 'plate fixed'.

Geocentric Datum of Australia 2020 (GDA2020)

A static coordinate datum based on the ITRF2014, fixed to the Australian tectonic plate at the epoch of January $1$, $2020$.

Dynamic Datum

A datum that changes with time to capture the temporal component of Earth's movements, considered as 'Earth fixed' and $4$-dimensional.

Plate Motion Model (PMM)

A model that accounts for the horizontal motion of the Australian tectonic plate, which moves approximately $7\,cm/year$ to the northeast.

Australian Terrestrial Reference Frame (ATRF)

A dynamic reference frame that uses the Australian PMM based on the site velocities of $109$ sites, providing a legally traceable link to the RVS Determination.

Australian Height Datum (AHD)

The vertical datum adopted by the National Mapping Council in $1971$, aligned to the approximate mean sea level (MSL) realised between $1966$ and $1968$ at $30$ tide gauges around the Australian coastline.

Australian National Levelling Network (ANLN)

A network of junction points and level sections created by combining levelling observations, used to establish the AHD.

AHD-TAS83

The version of the Australian Height Datum specific to Tasmania, based on the MSL for $1972$ at Burnie and Hobart.

Australian Vertical Working Surface (AVWS)

A component of the AGRS used for defining height throughout Australia in conjunction with the Australian Quasigeoid Model.