Survey control marks provide a reference framework which enables the position of earth related information to be expressed in a common coordinate system. They provide a practical basis for position fixing for a wide range of users who deal with geographically related information.
The following networks of survey control marks with directly measured Geocentric Datum of Australia 1994
(GDA94) horizontal coordinates have been established in Tasmania:
Number of Marks
Estimated Positional Uncertainty (metres)
700m (mostly in urban areas)
|Third and Fourth|
In total, approximately 7200 survey control marks have an Australian Height Datum (Tasmania) 1983 (AHD83) elevation value but approximately 2000 of these marks only have SCALED GDA94 horizontal coordinates.
Survey control mark information can be obtained from the Survey Control Marks Database (SurCom) and through LISTmap.
The current Standard for the Australian Survey Control Network produced by ICSM completes the transition from CLASS and ORDER to Uncertainty as the basis for evaluating and expressing the quality of measurements and
positions that was introduced in earlier versions of the Standard. The quality of Tasmanian Survey Control mark locations in SurCom is still indicated by CLASS and ORDER (as described in the SurCom Instructions page) and the transition to Positional Uncertainty for describing horizontal position quality will be undertaken in conjunction with the delivery of a modernised Australian Datum called GDA2020.
Coordinates on the new Australian geodetic datum, GDA2020, will be available from SurCom in approximately mid 2017. However GDA94 coordinates will be the default coordinates reported to users until the Tasmanian GDA2020 implementation plan is finalised. GDA2020 coordinates will be accompanied by a Positional Uncertainty value and a statement on the method of determination - rigorous or estimated.
From the Survey Control Marks Database you can:
- Select survey control marks by name or number
- Identify survey control in an area defined by grid or geographic coordinates
- Download a variety of reports, including one in .csv format that contains an extract of basic coordinate information about all control marks in Tasmania with survey accurate horizontal coordinates and/or heights.
From the LISTmap you can view available survey control over a map background and obtain survey control site summaries for individual control sites.
- Go to LISTmap
- The Survey Control Layer
will not display at this initial zoom scale – it will display automatically
when you zoom into your area of interest using any of the zooming options.
- Click on a survey control mark you are interested in and select the GDA94 Site Summary from the Identify Results box
When using survey control information, you must be aware of the warnings
associated with its use.
To report any issues associated with the Survey Control Marks Database (SurCom) or request additional information, please contact Scott Strong (contact details below).