• ACT spatial data is aligned with the Australian Geospatial Reference System (AGRS).
  • Spatial data professionals can access a range of resources to help calculate spatial data adjusted to ACT requirements.

ACT spatial data is now aligned with the Australian Geospatial Reference System (AGRS). If you need to perform geodetic calculations, you can use the resources below to adjust data to ACT requirements.

Calculations on GDA2020/MGA2020

These tools will help you perform geodetic calculations on:

  • Geocentric Datum of Australia 2020 (GDA2020)
  • Map Grid of Australia 2020 (MGA2020) projection

Australian Geospatial Reference System (AGRS)

GridCalc (GDA2020)

GridCalc (GDA2020) is available at the ICSM's GitHub repository. The package includes Combined Scale Factor (CSF) calculation and arc-to-chord corrections for GDA2020. The spreadsheet is suitable to use in the ACT.

The GitHub repository has other spreadsheets you can use to help you with:

  • transformation of spatial data between geodetic datums (e.g. GDA94 to GDA2020),
  • conversion of coordinate systems (e.g. Geographic (lat, lon) to Cartesian),
  • projection of data to a map grid,
  • common geodetic computations (e.g. azimuths and distances).

Calculations on AGD66/ACT standard grid

These spreadsheets will help you perform calculations on:

  • Australian Geodetic Datum 1966 (AGD66),
  • ACT Standard Grid projection.

These resources are modified from the ICSM Geocentric Datum of Australia Technical Manual v2.4 (GDA94) to include calculations on the ACT Standard Grid.

You'll find conditions of use within each spreadsheet.

Combined Scale and Height Factors

The Combined scale and height factors spreadsheet [37.0 KB] has been developed from the NSW LPI's GDA94 product. It will help you calculate:

  • elevation-dependent line scale factors for MGA94
  • scale factors on the ACT Standard Grid.
Distance Reduction (ACT)

The Distance reduction (ACT) spreadsheet [67.0 KB] has ACT spheroid details. It allows you to perform calculations 'on the surface' of the modified ellipsoid.

You can also reconstruct a slope distance that emulates a field-observed distance, corrected for ambient weather conditions.

Rigorous Formulae between Ellipsoid and Grid

The Rigorous formulae between ellipsoid and grid spreadsheet [86.5 KB] uses Redfearn's Formulae to calculate:

  • between the ACT Standard Grid Coordinates (SGC) and AGD66
  • easting, northing, grid convergence and point scale factor from latitude and longitude
  • latitude, longitude, grid convergence and point scale factor from easting and northing.
Formulae on the Grid

The Formulae on the grid spreadsheet [36.3 KB] can help you:

  • radiate via grid bearing and distance from a known mark to generate coordinates for another mark
  • calculate a join between a known mark and another mark
  • account for geodetic corrections and terrain differences.

It’s optimised for the ACT (added 610 meters to the ANS semi-major axis length). You'll find more details about this in the parameters and notes tab.

Formulae on the Ellipsoid

The Formulae on the ellipsoid spreadsheet [107.5 KB] has the ACT Ellipsoid's parameters added (a=6,378770m, f=1/298.25). The formulae are those of Vincenty.

If you have the azimuth and spheroidal distance, you can calculate:

  • latitude and longitude
  • reverse azimuth from a mark.

If you have the latitude and longitude of two marks, you can calculate:

  • spheroidal distance
  • forward and reverse azimuths between them.

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