A coordinate file can look precise and still be unsuitable for setting out the work. Before a crew relies on its eastings, northings or reduced levels, the project needs a shared reference system, dependable control marks and an agreed record of which information is current. Those decisions connect design, construction and the final asset survey.
Treat control as part of the project
Surveyor-General Victoria describes permanent survey marks as stable reference points carrying coordinate and height information aligned to national datums. Its survey-control guidance supports the whole project cycle, from planning and design through construction, as-constructed information and monitoring. [1]
For a site engineer, that makes control an interface to manage early. Establish who maintains the project control register, who authorises changes and how survey requirements appear in the work package. Discuss access, staging and the location of marks before temporary roads, stockpiles or excavation make the arrangement difficult to maintain.
Name the horizontal reference
Land Use Victoria identifies GDA2020 as Australia’s official geocentric datum and MGA2020 as the associated map projection. It also notes that GDA94 and MGA94 remain supported in Victoria. A file labelled only with a site name does not establish which coordinate reference system it uses. [2]
The practical handover should identify the datum, projection, zone, units and any approved project-grid relationship. Carry that information with the drawing or digital model, rather than leaving it in an email that the next contractor may never receive. If a local grid is used, its relationship to the wider survey framework needs to be defined by the project’s survey team.
When receiving legacy information, make the required reference system explicit before conversion. Land Use Victoria provides separate guidance for transforming GDA94 information to GDA2020. Changing a label on a file is not evidence that a transformation has been performed and checked. [2]
Keep the height reference explicit
Geoscience Australia identifies the Australian Height Datum as the national vertical datum and provides AUSGeoid2020 to support AHD height estimates from GNSS observations. The relationship between a positioning system’s height output and the project’s required levels therefore needs to be understood and documented. [3]
For example, a drainage work package might combine design levels, a survey export and machine-control information. Confirm that the three use the intended height reference before judging whether they agree. Any conversion, local adjustment or acceptance check belongs in the approved survey procedure, with the required evidence retained.
Check the mark and its information
Victoria’s Survey Marks Enquiry Service provides GDA2020 and former GDA94 coordinates, AHD heights, horizontal and vertical uncertainty estimates, mark status, observation methods, adjustment details and sketch plans. That is more useful than an isolated coordinate copied from an old drawing. [4]
Use the available metadata to frame a discussion with the surveyor about suitability for the task. A mark’s identifier, its recorded condition and the source of its coordinates should remain traceable. A position displayed to several decimal places does not, on its own, demonstrate that the underlying control meets the project’s requirements.
Protect the physical reference as well as the record. Land Use Victoria stresses the importance of maintaining permanent marks and provides guidance for engineers, councils and surveyors. Include relevant marks in work-area planning and raise potential disturbance with the survey team before the work reaches them. [1]
Make changes visible at handover
Civil Insight’s suggested control register would connect each mark identifier with the adopted coordinates and levels, reference systems, source, issue date, status and relevant verification record. The purpose is to make the current approved information easy to distinguish and trace.
When a mark is damaged, inaccessible or suspected of movement, record the issue and refer the affected work to the responsible surveyor for assessment under the project procedure. Any replacement or revised values should flow through the same document-control process as the design information used by the crew.
At work-package handover, ask for the survey basis as well as the finished coordinates. A future maintenance team needs to understand how the asset information relates to the control framework. Keeping that relationship clear makes the survey record useful beyond the day the work is set out.
Sources and photograph
[1] Surveyor-General Victoria, Victorian Survey Control Requirements; current resource links the December 2022, Edition 1 requirements.
[2] Land Use Victoria, Geocentric Datum of Australia 2020, updated 18 October 2024.
[3] Geoscience Australia, Australian Height Datum and geoid models.
[4] Land Use Victoria, Survey Marks Enquiry Service, updated 23 February 2026. Sources checked 4 November 2026.
Cover: surveying during concrete works at Powidz, Poland, 17 March 2022. Photo: Chris Gardner / U.S. Army Corps of Engineers, public domain. Illustrative international photograph.
The appearance of U.S. Department of War (DoW) visual information does not imply or constitute DoW endorsement.
