Why has my quarry moved? Moving to a new datum.
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Australia is moving to a new geodetic datum. This presentation explains why we are changing datums, the new GDA2020 datum and what you need to do to manage your spatial data.
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Why has my quarry moved? Moving to a new datum.
- 1. Why Has My Quarry Moved? Moving To a New Datum Presented by Erik Birzulis 19 September 2018
- 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, tree protection areas, underground services • Ensure coordinates are always accompanied by metadata
- 10. SUBSCRIBE www.landair.com.au/newsletter 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
- Have you heard about the quarry that accidently extracted past its’ extraction limit because the limit wasn’t marked on the ground correctly? What about the quarry that accidently destroyed some protected vegetation because the limits of this protection were not pegged properly? Hopefully my presentation will help you avoid these types of issues in the future! 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 and property boundaries. So today I’m going to talk about… I’m happy to answer questions during the presentation or at the end.
- 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.
- 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. These datums use latitude and longitude. The projection onto a flat surface of the GDA94 datum was MGA94 or Map Grid of Australia. Projections use Eastings and Northings. So GDA2020 is a plate fixed datum. Our grid of latitude and longitude move with the drift of our continent.
- 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. Because GDA94 is a plate fixed datum, where Oz moves GDA94 moves. BUT, satellites use a different datum.
- 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 always 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 will be getting more and more accurate. New technologies such as driverless cars will be measuring position accurately!
- So, for a change 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 . 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 GPS, GLONASS, Galileo and 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 and other consultants contain metadata with at least the coordinate system. Otherwise you could have issues with the location of your extraction and other limits. After 2020, more datum changes will be taking place so stay tuned…
- I’m happy to answer any questions now or please grab me during the conference. Otherwise my contact details are shown as well as a link to the official GDA2020 website.