
Australia's Entire GPS Navigation Is Off by 5 Feet - ghosh
http://www.atlasobscura.com/articles/australias-entire-gps-navigation-is-off-by-5-feet
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sctb
Previously:
[https://news.ycombinator.com/item?id=12188144](https://news.ycombinator.com/item?id=12188144)

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ungzd
But GPS is using WGS84 datum (usually). And they're changing their own local
datum. Nothing will be changed for GPS. It will still use WGS84.

Or there are weird Australian upside-down phones and navigators where GPS
calculates position in their local datum?

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tfm
Official local datum is GDA94, which is usually within about a metre of WGS84.
/me pats pocket protector

I think the idea here though is that the underlying terrain has scooted around
a bit in the last twenty years, so a new datum would save on the need to print
new maps and update the databases containing trig points and such. New
coordinates can be labelled as explicitly aligned to the new datum, get some
versioning happening.

Unfortuately it seems impossible to confirm this, because the Geoscience
Australia website does not appear to make any reference to this purported new
effort that's been making the rounds of late. New website layout, maybe their
CMS is broken.

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ellisv
This is similar to the difference between WGS84 and NAD83 (North American
Datum 1983). WGS84 is defined by the average of stations world wide while
NAD83 is defined in a way that it is relatively constant across North America.
NAD83 initially matched WGS84 but their difference increases each year by a
small amount (negligible for most consumer use). Of course there are other
differences between NAD83 and WGS84 as well (reference ellipsoids) and often
they are treated as the same by non-cartographers.

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abhikandoi2000
"“We’re fast approaching the day when people will expect accuracies of
centimeters in real time out of their handheld devices and then we’ll see a
lot of head scratching as things no longer line up,” Smith told Scientific
American three years ago. It looks like that day has arrived"

Has that day really arrived?

I doubt, given the fact that most consumer navigation systems are reliable
(directions on Google Maps, pick up on Uber and alike) as long as they are not
being blocked by major hurdles.

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rburhum
Think AR applications. Anything that requires accuracy that is not a "Pokemon
Go" game would need that.

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ChrisFoster
Ugh, all the recent articles I've seen on this are subtly or entirely wrong
about the reasons for a datum change (though this article is a lot better than
most).

It's possible to account and correct for most of the 1.5 meters when
transforming between GDA94 (the current Australian national datum) and
ITRF2008 (effectively what's used by GPS), and the transformation published by
Geoscience Australia is particularly simple, having only 14 parameters.

If you want to know about this from a reliable source, the ICSM site is the
place to go. They actually know what they're talking about, and their faq in
particular explains a lot of points of jargon and convention rather clearly:
[http://www.icsm.gov.au/gda2020/faqs-2.html](http://www.icsm.gov.au/gda2020/faqs-2.html)

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avs733
and shifting about 7cm per year. I did the math last night and realized that
Australia has moved further than I am tall since my birth. For some reason
that messed with my head.

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jacquesm
Wait until it shifts underneath you while you're standing on it and see how
_that_ messes with your head. The first time I experienced a very minor
earthquake the feeling did not leave me for weeks.

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avs733
I grew up in California...it has to be a big one to even wake me up nowadays.

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jacquesm
Here's to hoping you sleep soundly then!

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anotheryou
I wonder if google maps and OSM will be more accurate before or after the
change. (I guess after, be because the maps are probably based on satellite
images)

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maxerickson
It depends on how that imagery has been rectified. If they were aligned to
match up with the previous system, then any info derived from them would show
the offset.

