Construction Surveying Guideline

 

General

The following guideline has been developed to assist, project managers, superintendent's and their representatives in sourcing the survey construction needs of their projects using internal & or external support.

1 Surveying Personnel

At a minimum, survey personnel engaged on Main Roads construction projects should possess the following survey qualifications:

1.1 Contractor's Surveyor (SCC15)

• The contractor shall only use surveyors who are third party certified to AS/NZS ISO 9001:2015 .
• Alternatively, where the contractor uses their own in-house surveying resources, the contractor’s third party certified quality system should include surveying as a special process.
• A surveyor who is eligible for Membership of the Surveying and Spatial Sciences Institute as a certified engineering or mining surveyor shall be on-site at all times during survey work.

1.2 Superintendent's Surveyor

        As Above

1.3 Procurement of Survey Superintendents Surveyor for Audit and Support Services

Due to the irregular frequency of survey audit and support requirements on construction contracts, it is recommended that flexibility be built into the contract when engaging survey audit and support services for the lifetime of a project. In addition to flexibility other considerations should be given to response time, availability and mob/demob costs particularly on remote rural projects.

Main Roads primarily uses Engineering Technical Services (ETS) & or Contract c154_13 Survey and Mapping Panel Contract for procurement of survey and audit services:

• Contract C154_13 Survey and Mapping Panel Contract

Survey Services 1 Request Form: c154_13

• Period Contract for Engineering ,Technical Services
  The following ETS survey audit and support briefs are available for general use and may be modified to suit individual project requirements:

ETS Survey Audit and Support For AS2124
ETS Survey Audit and Support For Design and Construct

• Public Tender

Up to $5,000: - Direct Purchase
$5,001 - $20,000: - Request sufficient verbal quotations
$20,001 - $150,000: - Request sufficient written quotations. 
Above $150,000: - Open tender through a public advertisement

2 Construction Survey Control

The control network provides the basis for all design set out, measurement, compliance and audit surveys and therefore represents the critical datum reference for all road construction projects. The accuracy and quality of the network will directly affect the quality and accuracy of the final product and earthwork measurements for payment.

2.1 Establishment

2.1.1 Random Construction Control

A network of control points must be established over the proposed construction area.

All Construction Control shall be located, installed, and surveyed in accordance  with Main Roads Geodetic Control Survey standard.

2.1.2 Bridge works

The contractor must establish/nominate two random construction control points for each bridge site. The two marks will provide line, level, and origin for the bridge set out. Only these control points should be used for the bridge construction. This will eliminate the introduction of error from additional control and ensure a high level of relative internal precision as opposed to absolute location.

All Construction Control shall be located, installed and surveyed in accordance with Main Roads Geodetic Control Survey standard.

2.2 Re-establishment:

• If during the construction phase, control points have to be relocated or additional points installed, then these points shall be connected to the existing network and surveyed in accordance with the Main Roads Geodetic Control Survey standard.
• Computations of coordinates for these new control points shall be ancillary to the main traverse adjustment so that minor adjustments to previously fixed points are avoided.

2.3 Control Network Verification and Maintenance

• If the survey control has been established prior to the start of construction, the superintendent's representative should check to ensure the survey control points have not been disturbed or moved. An agreed value between principal and contractor for all road reference marks must be obtained prior to commencement of construction.
• Verification of the control network should be conducted periodically over the project duration by the contract surveyor. The frequency will vary in accordance with the environment. For example, control points located in marshland are more prone to subsidence than those located in pindan soils.
• If discrepancies are observed between adjacent control points and they appear undisturbed then this may indicate a need for network verification.
• The verification process should be clearly indicated in the quality plan.

2.4 Protection of Survey Marks

• Any road reference marks disturbed by the contractor during construction will be replaced by the contractor in accordance with Main Roads Geodetic Control Survey standard.
• The contractor will be responsible for all associated re-establishment costs resulting from any disturbance to existing established survey marks (BM’s,SSM’s and boundary/ fencing pegs) resulting from the contractor's activities under the contract.
• When the contractor is required to re-establish either of these types of mark, the following will apply:

(a) Cadastral Marks: In accordance with the Landgate regulations, a licensed surveyor must carry out all re-establishment cadastral surveys. The contractor will ensure that its licensed surveyor provides a "Regulation 25A certificate" for the superintendent upon completion of the survey.

(b) SSM's and BM's: The contractor must, through the superintendent, notify the Main Roads Senior Geodetic Surveyor who will arrange re-location and/or replacement through Landgate. Once the notification has been made, no delay to the works is required for the re-location and/or replacement of SSM's and BM's, unless directed otherwise by the superintendent.

2.5 Controlled Survey Mark Records

• The contract surveyor shall maintain a site listing of all the survey control mark coordinates, summary sheets and adjustments. A logbook shall be available indicating control point history clearly indicating where survey points have been disturbed or moved.
• This process should be clearly indicated in the quality plan.

3 Main Roads Supplied Survey Information for Set Out

To enable survey set out to be performed on a construction project, the following information should be supplied to the surveyors onsite. This is the minimum information required to perform all survey duties pertaining to the project.

• Digital Design Model
• A1 Construction Drawings
• Survey Control Point listing and Summaries: Note this information is also available from the “Survey Portal”
• Technical Specification
• String reports (992 MX output) and cross section reports (994 MX output) can be supplied if requested.

MX Digital Design Amendments

In the event of a digital design amendment, the following information should be supplied to the contractor:

• The amended full digital design in default MX genio format (cleaned of all designer construction strings);

and in addition

• A separate MX genio file consisting of just the amended design strings.

This enables the surveyor the option of updating his design model with just the amended strings (in the event significant work as been conducted on the surveyor’s model to date) or replacing the entire model.

4 Surveying as a “Special Process” – (AS 2124 Contracts Series 201)

Where the surveyors are not 3^rd Party Certified the construction contractor’s quality system requirements, Special Process procedures shall be prepared for all surveying and measuring activities. The contractor shall treat as a "special process" those surveying and measuring activities which:

• Verify conformance with all design surfaces, layers, dimensions, locations and positions within specified tolerances.
• Determine lengths, areas or volumes of materials, products or scheduled work items within specified tolerances.

In some cases the procedures provided may simply consist of a cross-reference to another section of the contract quality plan, or to existing procedures in the contractor's quality management system. In the former case, the cross-referencing must occur in both sections of the plan.

It is recommended that at a minimum, the following criteria are addressed in the quality plan, and where applicable cross-reference made to the relevant Survey and Mapping standards.

4.1 Qualifications, Experience and Responsibilities

4.1.1 Contract Surveyor (as defined in SCC 15 clause 28.5 ):

• Eligible for membership within the Surveying and Spatial Sciences Institute as a certified Engineering or Mining Surveyor,
• Knowledge and understanding of the different accuracy classes for control surveys, construction set out surveys and construction audit surveys,
• Knowledge and understanding of the different materials/construction methods to be used for each class of control point.

For Road Construction Contracts:

• Knowledge and understanding of the interpretation of MX genio digital design models and use of road construction plans, string reports, etc for construction set out.

For Bridge Construction Contracts:

• Knowledge and understanding of the interpretation of MX genio digital design models and use of bridge structural construction plans, etc for construction set out.
• Knowledge and understanding of deformation monitoring.

For Compliance (Audit) Surveying:

• Knowledge and understanding of analysis / statistical reporting of audit results against digital design models.

4.1.2 Surveyors Responsibilities- Typical

• Prepare set out data from plans and digital design, prior to and during construction.
• Identify any design errors or ambiguities and provide immediate feed back to project manager.
• Implement any design changes as advised.
• Collect and collate data to assist with reports and to monitor project progress.
• Ensure suitable survey procedures and accuracies are adopted for construction set out to satisfy required accuracies.
• Maintain a current survey control listing and update as necessary.
• Maintain and periodically calibrate survey instrumentation to ensure good working order.
• Maintain a complete record of surveys for inspection by the quality control officer or project manager.

4.2 Survey Equipment and Calibration

The following items need to be addressed:

• Storage and handling.
• Calibration regime.
• Types of equipment and fitness for purpose.
• Details of computer hardware / software for survey computations.

4.3 Survey Control Establishment and Maintenance

The following requirements apply to existing (Principal Supplied) control, and control installed under the contract:

• Verification of existing survey control network.
• Action required if control not in place or additional control to be installed.
• Maintenance of control - method / frequency of audit, records.
• The quality plan shall document the contractor’s intended compliance with the contract specifications and Main Roads Geodetic Control Survey standar for the maintenance and re-establishment of the control network.

4.4 Survey Methods for Set Out and Compliance

The following should be documented in any contract:

• Required accuracy, frequency and methodology for different stages of construction.
• Survey methods for major structures. i.e. All major structures will have separate fixed control stations established solely for setting out those structures. The relative position of the structure is more critical than the absolute.
• Survey methods for joint surveys.
• Survey methods for compliance surveys.
• Limits of vegetation clearing, pegged vegetation clearing and as constructed vegetation clearing area.
• Overall responsibility matrix defining the reporting line for the surveyor.

4.5 Survey Data Control

• Data storage/ backup / registration: who, when, where, why, how, must all be recorded.
• All digital terrain models shall be supplied in MX Genio format.
• All naturally occurring and man made features, both above ground and below, shall be captured, labelled and lodged in accordance with the Main Roads Survey and Mapping standard 67-08-43 "Digital Ground Survey".

4.6 Document Control

Documentation of the process for data storage,  back up, registration and controlled distribution of survey records on site. The procedure should include reference to:

• Certificates, sketches, tables and printouts prepared and endorsed by surveyors.
• Product conformance spreadsheets and reports.
• Field notes and calculations
• Calibration certificates and records.
• A register of all raw data files and the purpose for which they were taken.
• A register of all computer jobs (with a description of their purpose) created for volume calculation or set out, or verification.
• A register of field book allocations, issue dates and contents.
• A control registry which should include summary sketches, least square and third order level adjustments, field observations and quality statements, as stipulated in the Main Roads Geodetic Control Survey standard.
• Limits of vegetation clearing, pegged vegetation clearing and as constructed vegetation clearing area.

4.7 Reporting Standards for as Constructed Data (Compliance Surveys)

• Provide an audit schedule for each lot stipulating the product to be sampled; sampling frequency, size and observation density; and order of accuracy and confidence level.
• The quality plan shall include a sample of presentation for the compliance reporting.
• At a minimum the compliance report spreadsheet should include the Easting, Northing, Chainage and offset of the observed point and the corresponding ascon elevation and design elevation. The spreadsheet should include the elevation differences and a status of compliance for each sample point relative to design tolerances.

5 Construction Pegging

It is the responsibility of the contract surveyor to determine and undertake all construction pegging requirements. This section has therefore been included as a guide only based on past MRWA practice.

RTK GNSS complies with vertical accuracy to sub-grade only. It is not to be used for vertical set out on sub-base (where applicable), base-course final level or for structural set out (vertical or horizontal).

RTK GNSS provides an acceptable accuracy for horizontal set out of all sub-grade, sub-base and base-course pegging.

5.1 Construction Peg Set Out

5.1.1 Clearing Vegetation & Limits of Clearing

• The limits of vegetation clearing; Shall mean the clearing footprint to be communicated to the contractor.The limits of vegetation clearing shall be in accordance with the definition of designated and other areas required to undertake works under the contract.
• The Contractor shall receive the limits of vegetation clearing from the Superintendent in a shape file and/or in nominated drawings.
• The Contractor shall confirm receipt of the clearing line data to the Superintendent if required.
• The clearing line shall be pegged in accordance with the Pegging and Flagging Clearing Lines Principal Environmental Management Requirements. (D19#260830).
• All vegetation proposed to be cleared will be demarcated by PINK flagging tape on site prior to the commencement of project activities.
• Any vegetation or trees that are to be retained will be marked by WHITE flagging tape.
• Pegging is done by either stakeout from digital design model using RTK GNSS, string line radiation, offsetting from previously set out string lines, scaling and measuring from the plan using established features such as fences, edge of road, cadastral boundary etc.
• Accuracy required for this work is generally 0.5m or as specified by the contract documents or the project engineer.
• The pegged vegetation clearing line shall be sent to the Superintendent. The Superintendent will send this to the relevant Environmental officer. The Environmental officer will confirm that the pegged vegetation clearing line is within the “approved” clearing area.
• The format of the pegged vegetation clearing line shall be detailed in Spec 301.
• The as constructed vegetation shall mean the final clearing area that occurred over the duration of the contract.
• Vegetation outside the approved clearing area shall not be disturbed. The contractor shall take all necessary precautions to protect all tagged declared rare flora and nominated vegetation to be retained within the limits of clearing.

5.1.2 Batter Line

• The batter line shall be set out by either stakeout from digital design model using RTK GNSS, string line radiation or from cross section reports which define position and level.
• It is necessary to confirm the actual ground levels at points set out as any level discrepancy affects the batter grade, hence to string line radiation shall be used as a guide only.
• The toe of batter shall be located where the design batter slope from the hinge point intersects with the natural surface.
• Accuracy for batter pegging is generally 0.2m horizontally and 0.1m vertically or as specified by the project engineer.
• During construction of the batter, the shape is generally controlled either by the stepping method or fixed batter boards depending on the depth of the earthworks and the soil type.

5.1.3 Drainage Manholes, Gullies and Culverts

• Position is set out from the primary control and the pegs are placed at an offset to enable excavation and construction.
• Pegs are marked with the centre line offset, top of excavation offset and cut to invert level.
• To ensure the structure remains parallel to the kerb line, additional points may be required adjacent to the structure on the kerb line.
• Vertical accuracy in drainage works especially flat terrain, is critical and shall be surveyed to 5mm, or as specified in the contract document and or Project Manager.
• For sub soil drains and table drains the horizontal and vertical alignment of these structures is set out using the appropriate string line from the cross section report.

5.1.4 Formation

• The edge of formation is set out using the verge or shoulder strings and is placed by either stakeout from digital design model, string line radiation from the cross section reports or by offset from the existing centre line pegging.
• The shoulder string is usually offset by 0.3 – 1.0m to allow compacting machinery to operate to the edge of the formation. If the verge string is set out, no offsetting is usually required. These string lines form the basis of horizontal and vertical control for the pavement construction. It is the surveyor’s responsibility to maintain a continuous control on alignment and levels.
• The pegging interval for sub-grade should be no more than 20 metres and every 10 metres for sub-base and base-course.
• When machine guidance with GNSS or laser is being used then it is recommended that shoulder pegs are installed every 200 metres so that chainage is readily located.
• These must be installed to sub metre accuracy.

5.1.5 Priming, Sealing Edge

• Usually only one edge of the pavement requires marking out for the primer seal edge to ensure that spray run is on correct alignment and uniform.
• The alignment should be nailed every 10m with spring head nails and flagging under the nail for better visibility. Paint can also be used for better visual affect.

5.1.6 Kerbing

• Set out will be to face of kerb
• Kerbing alignments shall be surveyed in from control points and nailed with springhead nails and flagging.
• Intervals between nails should not exceed 15m on straights and 5m on large radius curves. On traffic islands and median noses, the interval must be adequate to define the alignment clearly and precisely.

5.1.7 Asphalt Pavement, Lane Marking

• Before asphalt paving can proceed, the proposed lane marking has to be established in order for the asphalt joins to coincide with the line markings.
• These may be set out using RTK GNSS.

5.2 Peg Colour Coding Systems

5.2.1 Urban Projects

• As a guide for all projects, construction pegs can be colour coded as follows:

5.3 Construction Peg Offests and Intervals

• Construction pegs will be located at fixed offsets from their design positions to avoid disturbance from machinery and to ensure compaction to the road edge. The offset distance shall be set by the project engineer and can vary from 0.3 – 1.0m from project to project.
• The pegging interval will vary according to the type of work and the construction environment. ( i.e thickness of the vegetation).
• Generally, the pegging interval is the same as the cross section drawings, however additional cross sections may need to be created from the digital model as required. Metropolitan projects usually peg at 10m intervals due to the increase in complexity of designs and drainage.
• Lighter traffic volumes and less refined tolerances result in most rural projects being pegged at 20m intervals.

5.4 Peg Annotation

• To define levels, self adhesive tape (eg insulation tape) is attached to each peg so that the bottom of the tape is at the construction level for that peg position.
• Due allowance shall be made for the offset distance when determining construction levels so that the level is placed with cross fall taken into account.
• In areas of cut the level placed on the peg shall be an even increment of 0.5m from the final level and the amount of cut to come down from the tape clearly marked on the peg.
• Pegs should be clearly annotated with a reference chainage relative to the master alignment, an offset relative to a reference design string and the reference design string label.

5.5 Peg Materials

• Pegs can be timber, aluminium, steel or plastic depending on environmental constraints and local needs.
• The pegs are driven firmly into the ground, positioned vertically and annotated with the respective chainage, offset from the centre line and design elevation.
• All pegs are to be placed within 50mm of their true horizontal position.

5.6 Pegless Construction

• Modern construction techniques are now utilising machine control technologies to enable them to construct with minimal pegging. Project Managers must be aware that GNSS technology will not enable final pavement level tolerances to be achieved and Laser systems must be utilized for final pavement accuracy.
• All AS2124 Contracts require pegging at a minimum as stated in General Requirements 100 Series (102.06).

6 Measurement Surveys

Measurement surveys or foundation surveys, are performed by the superintendent. This survey defines a particular surface of a feature for area and volume earthwork computations and subsequent schedule of rates payment.

• The ground model is captured in accordance with the Main Roads Survey and Mapping standard 67-08-43 "Digital Ground Survey".

Measurement surveys are used to determine:

• Actual earthwork quantities against design quantities (extent of cuts and fills, batter slopes etc).
• Identification of lots and layers for embankment fill (i.e. to control and ensure that all lots were tested for compaction).
• Calculating volumes of cuts and embankment fill.
• Calculating foundation areas for payment verification.

6.1 Embankment Foundation Surveys

Embankment foundation surveys (stripped ground surveys) are performed prior to the commencement of any earthworks or culvert work, and subsequent to clearing, removal of topsoil and compaction of the embankment foundation.

The contractor shall give the superintendent at least 24 hrs notice of when levelling is required for the purpose of earthworks measurement.

6.2 Joint Survey Requirement

• Joint surveys are performed when both the superintendent's and contractor's surveyor are present during the field observations. This minimises disputation.
• There is no set joint survey procedure for data capture, this is usually agreed on site between both parties. The observations are performed using either party’s total station and or RTK GNSS.
• Joint surveys can help eliminate issues relating to the ground model integrity in the event volume discrepancies should arise over the course of the project. It is recommended joint surveys be performed on all earthworks where the volumes are a schedule of rates payment.
• A hardcopy raw data output of the survey should be signed in agreement by both parties and forwarded, with the digital ground model, to the superintendents representative. The raw data output should include the date of survey and a descriptive of the lot location, survey methodology and equipment used.

6.3 Typical Measurement Survey Applications

6.3.1 Area Definition

• Clearing
• Spoil and borrow pits
• Sub-grade
• Bitumen removal

6.3.2 Volume Definition

• Borrow pits
• Rock
• Unsuitable material
• Stockpiles
• Bulk earthworks / mass haul.

6.4 Controlled Data Records

• Copies of all details including survey requests, raw data hardcopies and MX genio files of the digital ground model should be retained by the superintendent’s representative. The lodged information should be supplied to the superintendent’s representative in accordance with the lodged information and data format requirements stipulated in the Main Roads Survey and Mapping standard "Data Lodgement".
• In regards to joint surveys, a hardcopy of the raw data (unprocessed observational data  direct from instrument) is signed in agreement by both parties and forwarded, together with the MX genio digital terrain model, to the superintendent's representative. The raw data output should as a minimum include a date, lot location, survey methodology and equipment used. Control points used during the survey and appropriate check shots should be clearly defined in the raw data.

7 Compliance Surveys

Compliance surveys are undertaken by the contractor to ensure as constructed products comply with project specification tolerances. They are usually required on 100% of all as constructed surfaces and structures, as defined in the quality plan.

The compliance survey results provide the superintendent's representative with evidence for the release of hold points. The survey results should clearly indicate the product to be sampled; sampling frequency, size and observation density; and order of accuracy and confidence level. These criteria should be reflected in the contractors quality management system.

For compliance testing of formations and pavement layers, a tabulated spreadsheet is an effective means of presentation and should include as a minimum:

• Sample point location by Easting, Northing, Chainage and offset.
• As constructed elevation and corresponding design elevation.
• Elevation differences and a status of compliance for each sample point relative to design tolerances.
• Straight edge delineations.

In the case of structures and culverts, diagrammatic representations showing the as constructed
dimensions can be an effective means of presentation.

It is recommended that compliance survey observations be conducted at corresponding locations on each respective pavement layer i.e. chainage 13500 o/s 5.0 on sub-grade, sub-base, base-course, and asphalt. A simple reduction of elevations from the previous pavements compliance results at each corresponding location will provide a test for layer thickness in addition to surface level tolerance.

RTK GNSS complies with vertical accuracy for earthworks only (up to sub-grade). RTK GNSS is not to be used for vertical compliance checks on drainage structures, culverts, sub-grade, Sub-base, base-course, asphalt and bridge structures.

8 Audit Surveys

An audit is the process by which the superintendent satisfies himself that he is actually getting the product specified in the contract. In that sense an audit can be a desktop examination of information supplied by others, or it could be a comprehensive on-site corroboration of the contractors checking team, or some combination of field inspection and verification of contractors’ records.

8.1 Audit Frequency and Observation Density

• The superintendent's representative should be requesting a minimum level of audit on all survey and construction products and processes. The superintendent's representative will determine if the audit frequency can be reduced or increased depending upon the confidence obtained from the initial minimum auditing regime.
• Physical spacing of audit survey capture points should include a minimum 3 points per lane, and cross-section interval to be no more than 20m for sub-grade and sub-base, and no more than 10m for basecourse.
• Minimum audit can be defined as the minimum survey requirement necessary to establish a degree of confidence that the product being delivered complies with contract specification.
• Minimum audit may well constitute 100% sampling of the product depending on the origins, however, generally minimum audit is in the order of 5 - 15% of the product being audited.
• The frequency of product audits will depend upon the confidence obtained from the contractor’s compliance test results when compared with audit results.
• A recommended minimum survey audit surveillance plan is available for reference: Survey Audit Surveillance Plan

8.2 Survey Control Requirements for Performing Audit Surveys

• Construction audit surveys shall be conducted using verified primary construction control as supplied at the commencement of the project by Main Roads.
• Supplementary construction control established by the contractor may be utilised for audit purposes provided it has been verified for horizontal and vertical position relative to the primary control network and the Main Roads Geodetic Control Survey standard . A minimum of two adjacent control points from the original primary network shall be utilised for the verification.
• If auxiliary control is required for audit purposes then it shall be established in accordance with the Survey and Mapping Geodetic Control Survey standard with the exception of its construction. The construction of the control point will be determined by the superintendents representative based on whether its retention will benefit future audit or construction set out.
• The surveyor will be required to submit in conjunction with the audit results, all field measurements and adjustments pertaining to the verification/establishment of construction control for survey audit.
• It is recommended verification of observations be an inherent requirement for all construction survey audits.

8.3 Supplied Information

The following information will be required by the superintendent's representative surveyor to perform survey audits:

• Construction control coordinates and summary sheets.
• MX cross section (994 output) and geometric string (992 output) reports.
• A1 construction drawings
• MX digital design model (default 081 genio output) if requested.
• Technical  specification

8.4 Survey Equipment

• A valid calibration certificate shall accompany all survey equipment utilised for survey audit and will be made available on request to the superintendents’ representative.

8.5 Recommended Audit Survey Verification Procedure

• Prior to the submission of audit results for analysis it is recommended that an overlap section, be captured from adjacent control points between observation sets. Common points to both observation sets within the designated overlap area will be measured from each independent control point and the elevation residuals calculated.

  Figure 1.Field checking procedure for audit measurements.

8.6 Observation Considerations

It is ultimately the responsibility of the project surveyor to ensure suitable survey practices are adopted to achieve and/or better the survey accuracies required for each respective survey application.

The following considerations have been supplied as a guide for superintendent representatives:

• All surveying methods have intrinsic weaknesses and errors. This error is minimised with correct survey practices using appropriate survey instrumentation.
• It is recommended the following sighting distances using Total Station not be exceeded:

(a)   High precision structures (sub 2mm): 80m
(b)   Pavement formations (incl. asphalt): 130m
(c)   Earthworks: 260m

• These distances are based on ideal survey conditions when total station observations are able to achieve highest accuracy. The surveyor shall reduce the sight distances accordingly if weather conditions are extreme.
• All surveying methods have intrinsic weaknesses and errors. This error is minimised with correct survey practices using appropriate survey instrumentation.
• As a guide for audit measurement, the automatic level and staff should be capable of repeatedly measuring a pavement to 2mm (1mm for structures) for vertical accuracy at the 95% confidence level using third order levelling techniques. Whereas the 3" total station using the trig heighting method is realistically capable of repeatedly achieving 3 to 5mm for vertical at the 95% confidence level in ideal observing conditions where the distance does not exceed 130m.
• This error associated with trig heighting can be attributed to instrument or prism pole height error, instrument collimation, poor target bisection and poor target point selection.
• It is recommended the trig heighting method be used for audit measurement. It provides an acceptable level of accuracy for pavement auditing and is significantly quicker and more efficient than conventional levelling. The error associated with trig heighting can be attributed to instrument or prism pole height error, instrument collimation, poor target bisection and poor target point selection.
• Technology today enables the uploading of vertical and horizontal design alignments directly into survey instrumentation. This enables instantaneous comparisons of as constructed pavements with design in the field from random sampling. All observations can be referenced to the master alignment by chainage and offset.
• RTK GNSS complies with vertical accuracy for Sub-Grade only. It is not to be used for vertical set out on sub-base (where applicable), base-course or final level and structural set out.

8.7 Data Records and Presentation

• Audit surveys will require the submission of a digital MX genio file together with a tabulated spreadsheet summarising the results in a format stipulated by the superintendents’ representative. Additional diagrammatic representation may be required if the tabulated output is inappropriate. A copy of the least squares adjustment is to be included in the quality statement if additional control is established.

9 “Limits of Vegetation Clearing” Pegging/Set-out and As-Con Vegetation Clearing Survey

Prior to construction works, it is generally necessary/requested to delineate the “Limits of vegetation clearing” on site. (This may be referred to as the construction footprint, or extents of works.) The extents are generally the result of environmental/heritage extents/constraints for the project, along with the extents of the road design, with allowance for practical construction. 

The extents for set-pegging/set-out should be provided, or/and be available in the design model/data.

Subsequent to completion of construction, it is generally necessary/requested that the true extents of works/clearing/disturbance on site be surveyed (As-constructed vegetation clearing survey). This may then be compared against the limits of vegetation clearing, and any environmental or heritage constraints.

9.1 Pegging/Set-out of Limits of vegetation clearing on site. (Construction footprint/extents of works)

• Set-out pegs to delineate lines from provided coordinated data files / relevant strings in design model/data
• Horizontal accuracy of pegs/stakes +/-40mm (i.e. RTK GNSS survey positioning is suitable)
  • z/Height not required.
• Set-out stakes/pegs at maximum 40m interval, and
  • Sufficient stakes/pegs to result in no more than 300mm of deviation from line in the file/data provided
  • Include stakes/pegs at significant vertices/changes of direction.
  • Sufficient stakes/pegs to maintain line-of-sight visibility
• Use PINK flagging ribbon unless otherwise stipulated.
• Label strings stakes “CLEAR”
• Capture location of all established stakes/pegs (by RTK GNSS - +/-40mm accuracy)
  • Lodge this captured as-staked data to the Main Roads officer that requested the survey, as coordinated
    • comma delimited file, and
    • .dxf file.

9.2 As-constructed vegetation clearing survey (Cleared Extents)

• Positional accuracy as-con survey capture +/-40mm (i.e. RTK GNSS)
• Capture points at maximum spacing of 40m, and otherwise suitable to define the shape of the As-constructed vegetation clearing to +/-200mm accuracy
• Where site may not have obvious remaining vegetation, survey is to capture/delineate the extents of construction works/disturbance zone.
• Lodge data in MGA2020 UTM zone coordinates unless otherwise stipulated.
• Lodge as-con cleared survey polygons as
  • .dxf format and
    • Data in the .dxf must form closed polygons
  • Comma delimited file text/csv file of coordinates.