GDA vs GDA 94

Except for a small difference in the flattening term, the reference ellipsoid used with WGS84 is essentially the same as the Geodetic Reference System 1980 (GRS80) ellipsoid used with ITRF and hence GDA94.Given that the ITRF and WGS84 reference frames are also very closely aligned, for most practical purposes GDA94
and WGS84 coordinates can be considered the same and no transformation is required.In other words, when comparing GDA, WGS & ITRF datums, keep in mind that GDA94 coordinates are fixed as at the 1st January 1994 (epoch 1994.0) and that the
Australian plate is drifting in a north-easterly direction about seven centimetres per year. If we were to re-compute GDA now, the coordinates would about half a metre different.


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Hi Lukas

WGS84 and GDA94 are virtually identical.

You may come across some older maps that use an AGD66 Datum and these will have a 250 metre error, unless you change the GPS to AGD66.
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Doug/Mike,

I think Lucas' question was related to GDA (on his Garmin) Vs GDA 94 on EO maps. Coincidentally, that happened to be the subject line of his post :)))

Perhaps the following quotes from this website:
http://www.geoproject.com.au/gda.faq.html
will help:
"The Geocentric Datum of Australia (usually referred to as GDA94, or just GDA) is a coordinate system for Australia" (so Garmin is just abbreviating);
"Thus for most mapping, exploration and GIS uses, WGS84 and GDA94 coordinates will be the same. If you use a GPS receiver (alone, or with a differential service) and the GDA datum is not a built-in option, you can select WGS84."
"The difference between GDA94 and WGS84 is approximately 45cms in 2000."
Cheers, John

yer well hmmm Doug is spot on but wow what a complicated way to say... GDA and GDA94 are the same thing and that within the accuracy of your GPS (approx 5m) WGS84 is also the same thing