OSG Geodetic Surveying FAQs
OFFICE OF THE SURVEYOR-GENERAL
Geodetic Surveying FAQs
1. What does Geodesy mean?
Geodesy is the scientific discipline concerned with the measurement and representation of the Earth's shape, orientation, and gravitational field. Geodesy plays a crucial role in the determination and establishment of the geodetic reference frame, which is standardized coordinate system and datum for precisely representing the position of locations on Earth. The geodetic reference frame serves as the foundational basis for geodetic measurements and calculations, and as a framework to integrate and manage geospatial information.
2. Which is the South Australian geodetic reference frame or datum?
The Geocentric Datum of Australia 2020 (GDA2020) is a modern geodetic reference frame used in Australia for positioning and mapping. It is an update to the previous datum, GDA94. The Map Grid of Australia 2020 (MGA2020) is the official map projection for Australia.
More information about GDA2020 can be found on the Intergovernmental Committee on Surveying and Mapping (ICSM) website.
3. How can I transform a GDA94 coordinate into GDA2020?
To transform coordinates from the Geocentric Datum of Australia 1994 (GDA94) to the Geocentric Datum of Australia 2020 (GDA2020), you can use one of the three transformations methods recognised by the Intergovernmental Committee on Surveying and Mapping: A 7 parameter similarity (conformal) transformation, and two transformation grids.
The grids, online transformation service and tools can be accessed on the website of the Intergovernmental Committee on Surveying and Mapping.
4. What is the Australian Height Datum (AHD)?
The Australian Height Datum (AHD) is a vertical datum used as a reference for measuring elevations and heights in Australia. It serves as a standardized reference point for establishing vertical positions, primarily for surveying, mapping, and construction. The AHD provides a consistent and reliable reference for comparing elevations across different regions of the country.
More information about AHD can be found on the Intergovernmental Committee on Surveying and Mapping (ICSM) and the Geoscience Australia websites.
5. What is the Australian Geoid model or AUSGeoid?
The Australian Geoid Model, often referred to as AUSGeoid, is an irregular surface that approximates mean sea level. AUSGeoid can be used to converts ellipsoidal heights measured by GPS into heights above mean sea level referred to AHD, very useful for applications like mapping and surveying.
More information about AUSGeoid can be found on the Geoscience Australia website.
6. What are the Continuously Operating Reference Stations (CORS)?
CORS network is an essential geodetic infrastructure that ensures accurate positioning for users globally. It serves as a reliable reference frame, supporting various precise positioning and guidance applications. These applications include Surveying, Mapping, Precision Agriculture, Construction, Mining, Navigation, Natural Hazards and Emergency Response Services, and Scientific Research.
7. Where can I get CORS data from?
Geoscience Australia provides open access to the historic data and data streams observed from all stations that contribute to the National Positioning Infrastructure Capability.
Receiver independent exchange data (RINEX) from South Australian CORS can be accessed through the Geoscience Australia GNSS Data Centre.
Differential GPS real time data (DGPS) and real time kinetic data (RTK) from single stations of South Australia can be accessed freely through the Geoscience Australia AUSCORS NTRIP Broadcaster.
RTK Network services are available for access via subscription through a network of Australian based Value-Added Resellers (third-party service providers such as AllDayRTK, HxGN SmartNetAus, VRSNow, and Mondo Pin). These Value-Added Resellers combine the Geoscience Australia data streams with their own infrastructure to provide supported positioning services, which are available across most areas of South Australia with access to mobile phone coverage.
8. I need to calibrate my electronic distance measurement (EDM) instrument, do you provide a baseline for the calibration and a software?
Yes, we do. We provide a baseline to calibrate your EDM instrument along with the latest software. To book the baseline or obtain the latest calibration software please email us at DTI.SurveyOperations@sa.gov.au or call us at (08) 7133 2300.
View more information about equipment calibration.
9. Where can I find information about surveying procedures using GNSS to achieve the highest level of rigour and integrity in South Australia?
You can find information about surveying procedures using GNSS within the Guideline for Control Surveys by GNSS published by the Intergovernmental Committee on Surveying and Mapping (ICSM). This guideline promotes standardized GNSS surveying in Australia to maintain accurate geospatial data. It covers measurement collection, baseline derivation, factors affecting quality, real-time vs. post-processing, and recommended procedures.
10. Where can I find information about surveying procedures using total station to achieve the highest level of rigour and integrity in South Australia?
You can find information about surveying procedures using total station within the Guideline for Conventional Traverse Surveys published by the Intergovernmental Committee on Surveying and Mapping (ICSM). This guideline promotes using consistent conventional traverse surveys with advanced equipment like total stations or theodolite-EDM combinations to ensure accurate survey control marks in Australia. It offers recommended procedures and examples for assessing position uncertainties, enhancing data reliability.
11. Where can I find information about differential levelling procedures to achieve the highest level of rigour and integrity in South Australia?
You can find information about differential leveling procedures within the Guideline for Control Surveys by Differential Levelling published by the Intergovernmental Committee on Surveying and Mapping (ICSM). This guideline outlines the recommended equipment and procedures for conducting differential leveling, including examples for evaluating the uncertainty of estimated height differences between survey control marks.
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