What is a Class A Utility Survey?

The Main Roads Underground Utilities Survey Standard (67-08-121) has been structured to provide several different utility survey accuracy classes (A, B, C and D). These classes address the different types of utility surveys available during the design process and are presented as a series of options, not a course of compulsory action.

A Class A utility survey requires the utility to be “potholed” (exposed) and directly measured by a total station, theodolite or RTK GPS instrument. The expected accuracy for locating the utility is + 50mm for x, y & z.

Class A is the only method where the utility data gathered is considered “verified” as the utilities have been directly measured, and their position has been confirmed underground.

A Class A utility survey is costly and involves the risk of exposing and measuring the utility without damaging or affecting its’ integrity. The project manager and RM Surveys Service Locator must work together to determine where the utilities are located economically. Assumptions on pipe directions and joins to maintenance holes and structures must be minimised, and all practical efforts must be made to minimise disruption or damage.

Utility Locating Classes

ClassAccuracy ToleranceMethod of Detection and LocationRisk of Utility Damage During Project Works
Class A
Horizontal ±50mm, Vertical ±50mmUtilities potholed and traced / or surveyed at installationLow
Class B
Horizontal ±300mm, Vertical ±500mmUtilities located and marked (Electro / GPR)Medium
Class CHorizontal ±500mm, Vertical UnknownVisual utility identification (Pits & Manholes Surveyed)High
Class D
Horizontal & Vertical UnknownDBYD Plans or unknown sourceHigh
The following is a brief description of the accuracy classes within the Underground Utilities Survey Standard (67-08-121).


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