Plan orientation

Datum line

The datum line for a survey must be adopted in accordance with clause 12 Surveying and Spatial Information Regulation 2017. The orientation of the datum line must be derived from MGA co-ordinates except for an urban survey under clause 12(2)(c)(ii) Surveying and Spatial Information Regulation 2017. Further information may also be found in the Surveyor-General’s Direction – No. 7

Urban Survey

If there are 2 established survey marks within 300 metres of the land surveyed the datum line must be adopted from the grid bearing derived from the MGA co-ordinates of those marks.

If there are not 2 established survey marks within 300 metres of the land surveyed the datum line must be adopted from:

  • The grid bearing derived from the MGA co-ordinates of 2 established  survey marks with 1500 metres of the subject land, or
  • The grid bearing derived from the MGA co-ordinates of 2 permanent survey marks or reference marks within 300 metres of the land surveyed, as determined using an approved GNSS method, or
  • a survey plan which is filed or recorded by the Registrar General. This method does not require the orientation to be adopted from MGA.

The MGA co-ordinates referred to above must be obtained or determined no more than 6 months before the completion of the survey.

If the bearing of a datum line is derived from the MGA co-ordinates of established survey marks it must be verified by connection to at least 1 other established survey mark.

If the comparison of the connections to the verifying mark exceeds 40mm + 175ppm the survey must comply with clause 12(7) Surveying and Spatial Information Regulation 2017. See also Surveyor-General’s Direction – No. 7

Rural Survey

All rural surveys must have an orientation adopted from MGA.

If there are 2 established survey marks within 1000 metres of the land surveyed the datum line must be adopted from the grid bearing derived from the MGA co-ordinates of those marks.

If there are not 2 established survey marks within 1000 metres of the land surveyed the datum line must be adopted from the grid bearing derived from the MGA co-ordinates of:

  • 2 established survey marks within 5000 metres of the land surveyed, or
  • 2 permanent survey marks or reference marks within 1000 metres of the land surveyed, as determined using an approved GNSS method.

The MGA co-ordinates referred to above must be obtained or determined no more than 6 months before the completion of the survey.

If the bearing of a datum line is derived from the MGA co-ordinates of established survey marks it must be verified by connection to at least 1 other established survey mark.

If the comparison of the connections to the verifying mark exceeds 40mm + 175ppm the survey must comply with clause 12(7) Surveying and Spatial Information Regulation 2017. See also Surveyor-General’s Direction – No. 7

Recording the datum line

Clause 61 Surveying and Spatial Information Regulation 2017 indicates the method for recording the datum line. The terminals of the datum line must be show by distinguishing characters on the face of the plan and these characters must be identified in the survey certificate. If the terminals are Permanent Survey Marks the reference PM (number) or SSM (number) will be sufficient. If the terminals are another survey mark it is recommended they be identified by an alpha character e.g. “A and B” or “X and Y”.

The datum line must show the scaled ground distance calculated from the co-ordinates (or as is provided in the plan of origin) compared to the distance measured.