The Commonwealth, on behalf of ICSM, has decided to make available the GDA logo for use on GDA Compliant or GDA Compatible Products.  Both GDAy and the GDA Software Development Kit satisfy all GDA software product compliance requirements.

 

• Transforming between AGD84 and GDA94.
• Transforming between AGD66 and GDA94
• Software
• Distortion grids
• Support

The state datum in Queensland is the Geocentric Datum of Australia 1994 (GDA94) replacing the previously adopted Australian Geodetic Datum 1984 (AGD84).

Transforming between AGD84 and GDA94

Alternate methods for converting coordinates between these datums are discussed in the GDA Technical Manual (ICSM Web Site). The recommended method in Queensland is distortion modelling.

In some cases, users may have very specific metadata about their spatial information. Questions such as 'How the data was initially captured?' and 'How it has been manipulated over time?' provide the necessary metadata to consider the optimal method for the transformation of coordinates. If this metadata is not available, it is recommended that spatial information be transformed from AGD84 to GDA94 using distortion modelling.

Transformations between AGD84 and GDA94 using distortion modelling requires software and an AGD84 distortion grid. Both are available from this page.

Transforming between AGD66 and GDA94

It is recognised that a significant amount of spatial information is still related to the Geocentric Datum of Australia 1966 (AGD66). To support transformations between AGD66 and GDA94, an AGD66 distortion grid is also available from this page.

Software

ICSM maintains a List of Software Vendors (ICSM Web Site) and the current functionality regarding the transformation of coordinates to GDA94 for particular software programs. It is recommended that you consult your particular vendor regarding their implementation strategies for the adoption of GDA94.

Notes

• GDAy and the GDA Software Development Kit (SDK) have been designed for Windows 32-bit platforms and as such, they are not suitable for other operating platforms. Windows 64-bit and PocketPC versions of the GDA SDK have been developed and are available upon request by contacting Geodetic Support.
• GDAy and the GDA SDK are available free of charge, but are subject to License Agreement.

GDAy

GDAy is a Windows based utility for the transformation of coordinates using distortion modelling, in either interactive mode or file conversion mode. The software handles a range of ASCII formats as well as file formats of particular relevance to Queensland standards, eg 'QIF' format for DCDB data. Grid Extractor is included in the GDAy setup and may be installed independent of GDAy.

View the GDAy Readme for information on how to install GDAy.

• GDAy Readme.
• GDAy Self Extracting Installation (Self extracting executable, 3.2 MB) Quick installation for Windows platforms. Requires Windows Installer 2.0.
  Includes User Guide and Qld Grid
• GDAy CD (Self extracting executable, 7.6 MB) Complete installation for all Windows platforms. Installs Windows Installer 2.0.
  Includes User Guide and Qld Grid
• GDAy Users Guide (PDF, 629 kB)

GDA Software Development Kit (SDK)

There are certain circumstances where neither the propriety software and/or GDAy will satisfy specific user requirements. To accommodate and support special circumstances, a Dynamic Link Library (DLL) called "GCalc.dll" has been developed. GCalc is a Windows 32-Bit DLL and can only be used with programming languages supporting DLLs, eg ANSI C, C++, Visual Basic, Pascal or Fortran. To date, it has been tested only with Visual C++ and Visual Basic compilers.

All datum transformation methods exported by GCalc.dll apply the distortion modelling technique and, where applicable, a conversion of coordinates is performed between the supported coordinate types. Refer to the GCalc Technical Specification for details.

• GDA SDK (Self extracting executable, 583 kB) Suitable for all Windows platforms. Includes Technical Specification
• GCalc Technical Specification (PDF, 506 kB)

The GDA SDK contains the following files: GCalc.dll, GCalc.lib, GCalcext.h, GCalcext.bas, GCalc Tech and Spec.pdf

Distortion grids

The selection of a grid of distortions is clearly dependent on the current datum of the spatial information.

NOTE: The Distortion Grids have been designed for Windows 32-bit platforms and as such, they are not suitable for all operating platforms.

Datum AGD84-GDA94

• Queensland AGD84 distortion grid (GSB file, 2 MB)
• National AGD84 distortion grid (Zip archive, 7.9 MB)

Datum AGD66-GDA94

• National AGD66 distortion grid (Zip archive, 3.1 MB)

Qld_0900 Distortion Grid

The current version of the AGD84 Queensland distortion Grid is QLD_0900.gsb

Due to interpolation problems offshore and in remote areas of Queensland, the QLD_0400 has been recomputed. The worst case is shifts in the order of 10 metres between QLD_0400 and QLD_0900. These worst cases are in those areas offshore and in areas where the State Control Network is very sparse. Opportunity was taken to merge the Queensland data with South Australia in preparation for the National Grid.

To date Caloundra City Council has transformed their GIS system and as such analysis of the new grid was undertaken to assess the impact of the new grid for Caloundra CC. It was possible to retain the grid values impacting Caloundra CC to ensure identical transformations with both grids, however the grid will change in all other areas of Queensland.

Qld_0400 Distortion Grid

Whilst the QLD_1299 grid satisfied requirements for the Australian implementation, it did not rigorously comply with the Canadian implementation of the NTv2 file format. The variations only impacted the formatting of some header information contained in the first 10 lines of the binary file. The ASCII version of the file was not affected. Hence QLD_0400 corrected this formatting problem, ensuring compatible with all Australian NTv2 software as well as all international software implementing NTv2 distortion modelling.

Both the QLD_1299 and QLD_0400 grids give identical results.

Qld_1299 Distortion Grid

The QLD_1299 distortion grid (QLD_1299.gsb) was initially released in December 1999, substantially complying with the NTv2 file format.

Support

To obtain support for general matters relating to local installations and user privileges, seek advice from your local administrator.

For all technical matters relating to GDAy software installation, technical problems, software development issues, bugs or general feedback, please email Geodetic Support, Land Information Systems.

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