I use GIS software - what does GDA2020 mean for me ?

Computer based GIS software and indeed computers are a fairly recent addition to the spatial officers toolbox. It was only in the year 2000 that GIS software really came into being. And Australia has never had a datum change in that time. As a GIS specialist you are probably aware that when you get new data or a new layer you need to check what datum it uses. From 2017, you will have to check a little more closely… just checking for GDA or MGA or even AGD is no longer good enough, you will need to check the year too - MGA94 or MGA2020.

One potentially significant source of error is that the difference between GDA94 and GDA2020 is only 1.8 meters. It’s really hard to notice the difference, and consequently it may not be immediately obvious that there is an error. This is in contrast with the last shift in the year 2000 when the shift was around 200 meters - any error was immediately obvious.

And if you use GIS software, be aware of what datum each layer of your map is, you may need to re-project some of them. Your software supplier probably hasn’t set up a projection for GDA2020 yet. However, some software packages allow you to create your own custom projections. Depending on what level of accuracy you require you may be able to just transform your existing 94 datum.

However, it is a little more complicated for those who require sub centimeter precision. Different parts of Australia are moving are different rates, and also distorting slightly. These distortions aren’t large by some standards - the whole continent sits on a single tectonic plate, so we don’t have the issues that New Zealand or US or many other countries have. We don’t experience earthquakes, or plates moving together to form Himalayan scale mountains. Consequently, distortions are limited and fairly localised. However, there is a small amount of natural movement and also a degree of man-made ground movement caused activities such as mining and sub-surface water extraction.

All this seems a fairly poor excuse to cause so much upheaval for GIS professions. However, there is a fairly good reason for the change, and it all comes down to how technology have improved.

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