Plan orientation

Survey control and SCIMS

Current information on survey control can only be obtained from the Survey Control Information Management System (SCIMS).

SCIMS is a computer database of the State Survey Control network. The system identifies established marks within the vicinity of a proposed survey including both State Survey Marks (SSMs) and Permanent Marks (PMs).

Note  In some instances SCIMS shows SSM's as SS's. This is due to an error in the data entry fields within SCIMS. In these instances the new plan should identify the permanent mark as 'SSM....' however if 'SS' is used it will not attract a requisition.

Enquiries regarding information available through SCIMS, deferment of placing marks and exemptions to requirements should be directed to the:

Cadastral Management Unit (Bathurst)
Cadastral Integrity Group LPI
PO Box 143
Bathurst NSW 2795

T: 61 2 6332 8224  cmu@lpi.nsw.gov.au

Plan orientation

The orientation of a plan must be based upon the requirements set out in clause 12 Surveying and Spatial Information Regulation 2012. It will either be adopted from:

  • MGA (Mapping Grid of Australia) co-ordinates
  • a survey plan which is filed or recorded at LPI
  • Astronomical or GNSS (Global Navigation Satellite System) observations.

However, where established permanent marks are available within the specified distances the MGA co-ordinates of those must be used to determine the bearing for the orientation of the survey. The meridian of the plan will refer to 'MGA' see cl.12(1)-(6) Surveying and Spatial Information Regulation 2012.

Note  Surveys completed before 31 March 2000 may still use ISG Co-ordinates provided they comply with the provisions set out in the Surveyors Practice Regulation 2001.

Datum Line

MGA

The Survey (Geocentric datum of Australia) Act 1999 (commencing 31 March 2000) replaced the Integrated Survey Grid (ISG) with the Mapping Grid of Australia (MGA).

Established Survey Mark is defined in clause 5 Surveying and Spatial Information Regulation 2012 it,...... means a survey mark that is described on SCIMS as having a horizontal position equal to or better than Class 'C'.

Where two or more established survey marks exist within 300 metres of an urban survey or 1000 metres of a rural survey;

  • The survey must adopt two of those marks as the terminals of the datum line.
  • The bearing of the datum line must be derived from the MGA co-ordinates of those marks as provided in SCIMS (Survey Control Information Management System).
  • The MGA co-ordinates must be obtained from SCIMS within six months before the date of completion of the survey.
  • The derived bearing must be verified by angular, and (if practicable) distance, connection to at least one other established survey mark of a class equivalent to or better than the survey marks used to orient the survey.
  • If a comparison of the measured and calculated connections for the datum line reveals differences exceeding 20 mm + 100 ppm, the surveyor must:
    • connect to at least one other established permanent survey mark and show this on the plan, or
    • forward a report to the Surveyor General.

Note  When there are not two established marks with 1000 metres of a rural survey but there are two marks with a horizontal position equal to or better than Class D. The orientation may be derived from those marks.

Non MGA

If there are not two established survey marks within the required distance of the survey, the bearing used for orientation must be taken from:

  • a survey plan which is filed or recorded at LPI
  • astronomical or GNSS observations.

The plan must indicate the origin of the orientation see cl.12(7) Surveying and Spatial Information Regulation 2012 and any GNSS observations are derived from at least two independent connections to established survey marks or reference stations.

Recording the datum line

On a plan of survey a surveyor must define the terminals of the datum line adopted by using distinguishing characters and making reference to the nature of the marks referred to. The bearing and distance of this azimuth must be shown on the plan. Reference to the terminal points must be included beneath the survey certificate on the Administration sheet.

Where the orientation adopted is MGA a schedule of co-ordinates showing values, zone, accuracy class and order, date, combined scale factor and source of all the established permanent survey marks used for orientation purposes must also be shown on the plan see cl.61(1)-(3) Surveying and Spatial Information Regulation 2012.

Schedule of co-ordinates

All permanent survey marks and bench marks shown on the plan must be listed in a schedule of co-ordinates. The schedule must include:

  • the number of each permanent survey mark and bench mark shown in the plan
  • the Easting and Northing co-ordinates of each mark
  • the accuracy (Class and Order) of the co-ordinates of each mark
  • if the plan shows a bench mark, the reduced levels for each mark and the accuracy (Class and order) of the reduced level
  • the combined scale factor for the co-ordinates (the mean of the CSF for all marks may be shown as in the example)
  • the MGA zone in which the land is situated
  • the date the co-ordinates were obtained from SCIMS.

Surveying and Spatial Information Regulation 2012 clauses 35 (1)(b), 61(2) and 62

Mark

MGA Co-ordinates

Class Order AHD AHD Class AHD Order Method Origin

Easting

Northing

PM 622 342424.711 6259416.278 B 2 4.578 LB L2 SCIMS
PM 6 23 341417.817 6259711.967 C 3 5.48 LB L2 SCIMS
SS 51647 341227 6259043 U N/A 5 U N/A Hand held GNSS Placed

BM 1

Triangle on kerb

341408.8 6259489.9 U N/A 4.72 B N/A Hand held GNSS & trig levelling Placed

Combined Scale Factor 0.999910
Zone 56
Adopted from SCIMS 25 October 2012