Map Grid of Australia 1994. Universal Transverse Mercator projection of the Geocentric Datum of Australia 1994. MSL Mean Sea Level A tidal datum derived from the arithmetic – mean of hourly heights of the sea at the tidal station observed over a period of time (preferably 19 years). NGRS National Geospatial Reference System is Australia’s – authoritative, reliable, high accuracy spatial referencing system. It includes the GDA94, AHD71 and AHD-TAS83 datums. PCG ICSM Permanent Committee on Geodesy Precision A term used to quantify the variability of a measurement or computed value. If several measurements are taken repeatedly to represent the same quantity, precision is used to refer to the degree of closeness or conformity of those measurements to each other. Quasi-geoid A reference surface based on the Earth’s gravitational potential. The geoid and quasi-geoid are approximately the same surface over the oceans but diverge over land due to the influence of topography. Survey control mark A monument that provides a physical realisation of one or more datums. The Standard This document, known as the Standard for the Australian Survey Control Network Special Publication 1 (SP1). – Uncertainty In accordance with the GUM meaning, uncertainty in this Standard means doubt about the validity of a measurement or result of a measurement (e.g. a coordinate). It is an indication of how wrong a value may be and is used in this Standard to quantify the level of survey quality. Uncertainty is expressed as a standard deviation in the International System of Units (SI) expanded to the 95% confidence level. Uncertainty, Positional The uncertainty of the horizontal and/or vertical coordinates (PU) of a survey control mark with respect to datum. Uncertainty, Relative The uncertainty between the horizontal and/or vertical (RU) coordinates of any two survey control marks. RU can be expressed in SI units at the 95% confidence level, or in a proportional form such as a ratio of uncertainty per unit length or survey misclosure. Uncertainty, Survey (SU) The uncertainty of the horizontal and/or vertical coordinates of a survey control mark independent of datum. That is, the uncertainty of a coordinate relative to the survey in which it
Map Grid of Australia 1994. Universal Transverse Mercator projection of the Geocentric Datum of Australia 1994. MSL Mean Sea Level – A tidal datum derived from the arithmetic mean of hourly heights of the sea at the tidal station observed over a period of time (preferably 19 years). NGRS National Geospatial Reference System – is Australia’s authoritative, reliable, high accuracy spatial referencing system. It includes the GDA94, AHD71 and AHD-TAS83 datums. PCG ICSM Permanent Committee on Geodesy Precision A term used to quantify the variability of a measurement or computed value. If several measurements are taken repeatedly to represent the same quantity, precision is used to refer to the degree of closeness or conformity of those measurements to each other. Quasi-geoid A reference surface based on the Earth’s gravitational potential. The geoid and quasi-geoid are approximately the same surface over the oceans but diverge over land due to the influence of topography. Survey control mark A monument that provides a physical realisation of one or more datums. The Standard This document, known as the Standard for the Australian Survey Control Network – Special Publication 1 (SP1). Uncertainty In accordance with the GUM meaning, uncertainty in this Standard means doubt about the validity of a measurement or result of a measurement (e.g. a coordinate). It is an indication of how wrong a value may be and is used in this Standard to quantify the level of survey quality. Uncertainty is expressed as a standard deviation in the International System of Units (SI) expanded to the 95% confidence level. Uncertainty, Positional (PU) The uncertainty of the horizontal and/or vertical coordinates of a survey control mark with respect to datum. Uncertainty, Relative (RU) The uncertainty between the horizontal and/or vertical coordinates of any two survey control marks. RU can be expressed in SI units at the 95% confidence level, or in a proportional form such as a ratio of uncertainty per unit length or survey misclosure. Uncertainty, Survey (SU) The uncertainty of the horizontal and/or vertical coordinates of a survey control mark independent of datum. That is, the uncertainty of a coordinate relative to the survey in which it