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Survey Control -provides the physical (mark on the ground) positional framework for spatially referenced projects. It is required for all survey applications such as digital ground surveys for design, construction set out and cadastral backgrounds.
There are three types of Survey Control used on Main Roads projects which have different in accuracies, use and appearance. They are:
1. Standard Survey Marks2. Road Reference Marks3. Minor Control Marks
The application and suitability of each type of Survey Control can vary depending on your project requirements. In some circumstances the existing control may be adequate for your project needs. For your special project needs or for further clarification please contact the Senior Geodetic Surveyor.
SSMs are the basis of the survey control framework within Western Australia and are controlled by Landgate. Generally, SSMs are the most accurate and permanent type of survey control used by Surveyors.
All survey work which requires the installation of new or the relocation of existing SSMs must be completed to Landgate Standards and registered through the Senior Geodetic Surveyor. SSMs are registered survey control points and are protected by the Standard Survey Mark Act 1933. It is an offence to move or destroy SSMs without permission.
Main Roads uses SSMs as the base survey control for most spatially referenced projects and typical spacing of SSMs in rural areas is between 2 and 5 km. In addition, SSMs form the basis for the road reserve boundary definition in remote rural regions. In urban areas, where the existing geodetic control network is extremely dense, sufficient SSMs are usually in existence to meet project requirements.
To maintain the integrity of the SSM control framework, all SSMs that will be disturbed by road works must be relocated prior to the disturbance of the mark. It is the responsibility of the Project Manager to identify all SSMs located within the project area and to notify the Senior Geodetic Surveyor of those likely to be affected by road works.
My Landgate Map Viewer - Provides a direct link to the Standard Survey Marks and Benchmarks database at Landgate.
Typical Rural SSM
RRMs form the majority of survey control established by Main Roads to provide horizontal and vertical control on all road construction projects. Summary Sheets identifying the location and coordinates of the RRMs can be supplied to the road construction contractor at the beginning of the construction phase and are available from the Mainroads WA Survey Portal. www.mainroads.wa.gov.au/portal/survey
RRMs are used as the primary base control for all set out works, additional control establishment and construction audit and can be established either during the data capture for the design phase or just prior to construction.
RRMs can also be utilised for digital ground surveys. Depending on project lead times between the design and construction phase, RRMs can be established to supplement Minor Control Points for the capture of the Digital Terrain Model used for design. (Refer to Minor Control Points below for additional information).
RRMs are connected to Landgate's Standard Survey Mark network and are registered with Main Roads. All RRMs are differential levelled to the Australian Height Datum (AHD).
Typical Rural RRM
These control marks are generally established at a spacing of 400 metres. The type of mark and location of witness plate should ensure the safety of the surveyor and the public at all times.
Construction for Urban marks as per Appendix A must be adhered to for all RRMs installed in metropolitan area and country towns or where the construction of these marks could expose the Surveyor and the public to safety risks.
RRMs may be placed under a plastic or concrete Reticulation type cover to improve the amenity and aid in future re-location and use.
In rural situations RRMs can be established as per Appendix B or C.
An indicator, for easier location of the RRM, shall be used, typically in the form of a star iron picket, 1.5 metres long, with a stamped RRM witness plate attached. The star iron picket shall be driven in behind each RRM only if the installation of the indicator will not compromise the safety of the surveyor or public.
Brass Plaques and witness plates may be obtained from the Main Roads Senior Geodetic Surveyor (Phone 9323 4152).
These control points will usually be required every 3 to 6 km in the project area depending on terrain. Thus the types of typical marks at Appendix B and C may be replaced by more solid construction pillars with stainless plate and forced centering to facilitate efficient instrument setup (Photos below). These marks need to be coordinated as accurately as possible into the State Geodetic network as well as 12√k levelled - prior to the start of construction.
If the pillars are within the road corridor or on Crown land, they could become SSMs in their own right with appropriate numbers obtained from the Survey Section of Landgate. Advice from Landgate should be sought on what raw survey data they require for lodgement to enable the new SSMs to be incorporated into the State Geodetic network.
During construction it will be necessary to place coordinated control (RTK horizontal accuracy)at 300 metre intervals for machine benching. These marks may be of less-permanent type (eg. stake or spike flush, ideally set in concrete) and may be MCPs as allocated by the Senior Geodetic Surveyor.
Such marks will need to be spirit levelled as per Differential levelling Standard as accurate height for final road surface is critical. Refer to the Standard for Differential levelling.
Station summaries will be required for only RRM control placed, unless there is a request to provide them for other marks placed as part of the contract.
This type of construction would typically be carried out on remote roads where no level control is required. Accurately coordinated(X,Y,Z) RRMs to serve as Base stations for horizontal control would only be required at 2 to 4 km intervals depending upon topography, with high open locations being the most suitable.
Sandstone road construction-typical remote project utilising RTK GPS
MCPs are the third tier of survey control and are only to be used for the capture of digital terrain models (i.e. Digital Ground Survey) and not for construction projects as they are not constructed to the same quality as RRMs.
However, if the final design alignment is known at the time of Digital Ground Survey, it can be more cost-effective to install RRMs every 400 metres and infill the spacing with MCPs to reduce the duplication of survey control. Please contact the Senior Geodetic Surveyor for further advice on this matter.
MCPs shall be installed at a maximum spacing of 260 m along the alignment of the project to meet the requirements of MRWA Digital Ground Survey Standard 67/08/43 and can vary in physical appearance depending on project specifics. (eg spike in bitumen, star iron picket in road shoulder sunk 0.2 m, wooden peg or other similar marker.)
Please refer to the MCP Standard for more detailed information.
Sample MCP Summary sheet
Project Managers should be aware of their and the contractor's responsibility to protect survey marks. Failure to do so may result in penalties which are provided by law for the removal or disturbance of any survey markers. The information below should be made available to contractors on all projects and included in the contract specifications:
The Contractor's attention should be brought to the existence of cadastral survey marks defining property boundaries and the road reserve, Road Reference Marks (RRMs) for construction control and State Survey Marks (SSMs) or Bench Marks (BMs) established on or within the vicinity of the Works.
The Contractor will be aware of these marks and shall be responsible for all associated re-establishment costs as a result of any disturbance to these marks resulting from the activities under the Contract.
The Contractor will follow the following procedures when re-establishing these marks.Cadastral Marks: All re-establishment surveys are to be carried out by a Licensed Surveyor and a "Regulation 25A certificate" provided to the Superintendent in accordance with the regulation.
Road Reference Marks: All re-establishment surveys are to be undertaken in accordance with Mainroads Standard 67-08-36 "Road Reference Marks" SSMs and BMs: Notify Main Roads WA, Senior Geodetic Surveyor, who will arrange re-location and/or replacement through Landgate. Mainroads Standard 67-08-35 "Standard Survey Marks" applies.
URBAN AND RURAL TOWNSITE AREAS
ROAD REFERENCE MARK- PERMANENT MACHINE CONTROL