Why has my site moved? Australia's new coordinate system
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Australia has a new coordinate datum called GDA2020. This means that when you receive a CAD file, coordinate listing or spatial data, if you do not know the coordinate system then those coordinates and data are approximate at best.
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Why has my site moved? Australia's new coordinate system
- 1. Why Has My Site Moved? Moving To a New Datum Presented by Erik Birzulis
- 2. Overview 1. What is a datum? (How maps work) 2. What’s the problem? 3. A new datum GDA2020 4. What do I need to do? (Metadata)
- 3. What is a datum? • Reference system or starting point for measurements • The system that underlies location information • Latitude and longitude tied to known reference points
- 4. What is the problem? -Old datum GDA94 • Geocentric Datum of Australia 1994 • Plate Fixed (fixed to Australia’s surface) • National grid of latitude and longitude coordinates that move with the drift of the continent • Where Australia goes GDA94 goes https://www.icsm.gov.au/datum/what-changing-and-why
- 5. What is the problem? -Old datum GDA94 • GDA94 was adopted in 2000 • Australia has moved 1.5 metres north east • Australia moves 7cm per year • Where Australia goes GDA94 goes • Satellite positioning
- 6. What is the problem? -Satellite positioning • Satellites use a different datum • Fixed to centre of Earth (not surface) • More accurate consumer positioning • Driverless Cars • 7cm per year https://www.icsm.gov.au/datum/what-changing-and-why
- 7. A New Datum -GDA2020 • Still a plate fixed datum • Will align with satellite datums in 2020 • 1.5m to 1.8m difference https://www.icsm.gov.au/datum/what-changing-and-why
- 8. Intergovernmental Committee on Surveying and Mapping (ICSM) and Small Island Studio
- 9. What do I need to do? • Know your datum! • Extraction limits, heritage areas, non disturbance limits, landfill licence boundaries, underground services • Ensure coordinates are always accompanied by metadata
- 10. SUBSCRIBE www.landair.com.au/newsletter-signup/ Erik Birzulis erik@landair.com.au 1300 130 158 https://www.icsm.gov.au/what-we-do/geocentric-datum-australia
- 11. Land, Engineering and Aerial Surveying Services
Editor's Notes
- Hello, Thanks for watching. My name is Erik Birzulis and I’m the managing director of Landair Surveys. We provide land and aerial surveying services for corporate and government clients in the infrastructure, environment, property and resources industries. Why should you care about a new coordinate datum? Because if you have the wrong datum, your boundaries, infrastructure and other limits will in the wrong spot! Today I’ll be talking about Australia’s new coordinate datum.
- Australia is moving towards a new datum. This will change the coordinates of features on our current maps, such as quarry extraction limits, landfill licence boundaries, native vegetation non disturbance limits and property boundaries. So today I’m going to talk about…
- So, the basics: A geodetic datum is a tool used to define the shape and size of the earth, as well as the reference point for the various coordinate systems used ... Historically datums were tied to fixed points such as this trig station. Most of you would have seen these around; they mark a point of known coordinates. This is a photo of a trig station one of our surveyors took near a quarry in north east Victoria.
- The previous datum that we had been using since 2000 in Australia was called GDA94 or Geocentric Datum of Australia 94. Before then we used AGD84 and AGD66. All geodetic datums use latitude and longitude to define location. The projection of a datum onto a flat surface is called a map projection. The projection of the GDA94 datum is MGA94 or Map Grid of Australia. Projections use Eastings and Northings to define location. Generally eastings and northings are shown on large scale maps and plans and are used in all CAD packages So..
- The issue we have is that Australia’s tectonic plate moves. Since 2000 when GDA94 was adopted Australia has moved by 1.5 metres. Our continent moves by 7 cm per year towards the north east. Because GDA94 is a plate fixed datum, where Oz moves GDA94 moves. BUT, satellites use a different datum. AND that is the problem!
- Satellite positioning systems such as GPS base their coordinates on a framework that is fixed to the centre of the Earth, not on reference points fixed to the surface. So in the satellite's eyes, the coordinates for features on moving parts of the Earth's surface, such as Australia, are continually changing by 7 cm per year. In the past this has not been a problem as consumer devices could only measure accurately to several metres or more. But, consumer devices such as phones and car navigation systems will be getting more and more accurate. New technologies such as driverless cars will be measuring position accurately!
- So, the federal government and all the states worked together. The Intergovernmental Committee on Surveying and Mapping has decided on a new datum. GDA2020 was officially defined as Australia’s new geodetic datum in December 2017. This new continent-fixed datum will bring the coordinates of Australia’s mapped features back into line with global systems in 2020 . Still a plate fixed datum but coordinates will line up with coordinates from satellite systems in 2020. Depending on where in Australia you are, GDA2020 coordinates differ from GDA94 coordinates by approximately 1.5 to 1.8 metres and are more closely aligned with the reference frameworks used by modern satellite systems – such as Americas GPS, Russias GLONASS, European Galileo and Chines BeiDou.
- Here is a video summarising what I’ve said so far..
- A coordinate with an unknown datum is an approximate location at best! You need to know if coordinates are based on GDA2020, GDA94 or even older datums. Insist that all plans and data you receive from surveyors, engineers, geologists and other consultants contain metadata with at least the coordinate system. Otherwise you could have issues with the location of your infrastructure and boundaries After 2020, there will be more datum changes, including a dynamic datum to keep the plate fixed coordinates aligned with the GPS coordinates. I’ll talk about this in a future presentation, so stay tuned…
- Thank you for listening! If you have any questions at all, please don’t hesitate to get in touch!