Survey Control Marks

User Instructions

  1. Selection of Survey Control Marks
  2. Summaries and Reports
  3. Explanation of Terms and Abbreviations

1. Selection of Survey Control Marks

1.1 Survey control marks may be selected by entering information in one of the following fields:

An asterisk (*) may be used as a wild card in these fields and a comma may be used to specify multiple entries.

1.2 Survey control marks may also be selected by specifying the bounding coordinates of a rectangle.

1.3 You may filter the marks that will be returned by including only, or excluding, marks with certain attributes.

1.4 Click on the Search button or hit Enter to start the search process.

2. Summaries and Reports

2.1 Choose a Horizontal Datum

Before selecting a summary or report a horizontal datum must be specified. The default datum is GDA94.

2.2 Survey Control Site Summary

This contains information relating to all Survey Control Marks at a Survey Control Site. It includes:

2.3 Survey Control Mark Summary

This contains information relating to an individual Survey Control Mark. It includes all the above information with the exception of site ID and site access details.

2.4 Basic Mark Report

This is a plain text report in available in fixed field or comma separated format. It contains the following information:

3. Explanation of Terms and Abbreviations

These are the terms and abbreviations used in SurCoM Summaries and Reports.

Height Class

This is a measure of the precision of the heights in a survey control network and is tested by examining the results of a minimally constrained least squares adjustment. It depends on the network design, the instruments used and the survey methods used. This information is generally not available for survey control marks in Tasmania. The survey method is often used to give an indication of the Height Class of a survey control mark. The following abbreviations are used in Basic Mark Reports:

DIR Direct measurement. By tape, or taped measurement and vertical angle.
GPS Global positioning system
LEV Differential levelling
RES Resection
INT Intersection
TRG Trigonometric levelling
UNK Unknown

Height Order

This is a function of the Class of the levelling, the order of the heights used to constrain levelling adjustments, and in the case of differential levelling, the loop closures. The following abbreviations are used in Basic Mark Reports:

3RD Third order
4TH Forth order
L3RD Third order differential (12 root K)
L4TH Fourth order differential (18 root K)
PRV Provisional. Determined using a survey method that does not contain redundancies.

Horizontal Class

This is a measure of the quality of the positions in a survey control network and is tested by examining the results of a minimally constrained least squares adjustment. It depends on the network design, the instruments used and the survey methods used. Marks with GDA Coordinates are classified as follows:

Class A National and state geodetic surveys.
Class B Densification of geodetic surveys.
TRA Determined from AGD66 coordinates using a precise transformation process.

The information required to assign Horizontal Class is generally not available for survey control marks with AGD coordinates. The survey method is used to give an indication of the quality of the positions. The following abbreviations are used in Basic Mark Reports:

CRA Closed radiation
GPS Global positioning system
INT Intersection
RAD Radiation (unclosed traverse)
RES Resection
T/T Triangulation/trilateration
TRA Traverse
UNC Unclosed traverse

Horizontal Order

This is a function of the Class of a survey and its conformity with existing network coordinates determined from a least squares adjustment. It involves an assessment of the sizes of the semi-major axes of relative standard error ellipses. The maximum sizes of the semi-major axis allowed for stations 1 km apart (95% confidence level) are as follows:

1ST 22 mm
2ND 44 mm
3RD 88 mm
4TH 147 mm

Two other statements of Horizontal Order are also used:

PRV Provisional. Coordinates determined using a survey method that does not contain redundant observations.
SCA Coordinates scaled from a map.

Positional uncertainty is a value available to internal users which specifies accuracy more precisely.

Reference Mark

A survey mark placed in the vicinity of a survey control mark for the purpose of preserving the horizontal and vertical position of the mark. If a survey control mark is destroyed or damaged the reference mark may be used to re-instate it, or to provide an alternative instrument stand point.

Survey Control Mark

A permanently monumented survey mark with horizontal coordinates and/or height of known accuracy. It usually takes the form of a disc made of non-ferrous material, such as bronze, with a mark identifier engraved or stamped on it.

Survey Control Site

An unbounded locality containing one or more Survey Control Marks.

Status

Survey mark status.

The following abbreviations are used in Basic Mark Reports:

D Destroyed
N Reported "not found"
R Mark destroyed but reference marks remain

Target

A structure erected over, or adjacent to, a Survey Control Mark. It enables directions to be read to the mark or adjacent structure using a theodolite or similar surveying instrument. The following abbreviations are used in Basic Mark Reports:

BCN Beacon
CRN Cairn
FC Fire cabin
FT Fire tower
LH Lighthouse
LT Navigation light
MON Monument
MST Mast
MTT Mobile telephone tower
MWT Microwave tower
PIL Pillar
PO Pole
RT Radio tower
SPI Spire
TVT Television tower

Vertical Reference Mark

A survey mark placed in the vicinity of a survey control mark for the purpose of preserving its vertical position. If a survey control mark is destroyed or damaged the reference mark may be used to provide an alternative instrument stand point. In survey control site and mark summaries the abbreviation VR mark is often used.