Re:Australia Is Drifting So Fast GPS Can't Keep Up
by sigmar on Saturday September 24, 2016 @03:22PM
(#12572189)
>Corrections have been made to its latitude and longitude four times over the past 50 years, the Times reports. The last adjustment there, in 1994, was about 656 feet.
>The next adjustment is said to be due by the end of this year, on the order of 4.9 feet.
I don't understand. It moved 4.9 ft since 1994, but was moving more quickly before then? The NYTimes article doesn't seem to clarify this either. Were pre-1994 commercially available maps not based on satellite readings of lat/long?
Different datums (models of the shape of Earth) will put the same coordinates at different places. The 656 feet would be the average shift required to reconcile coordinates using the previous datum with coordinates using the new one (which is based on WGS84, the modern global datum).
Re:Australia Is Drifting So Fast GPS Can't Keep Up
by teh_klev on Saturday September 24, 2016 @03:44PM
(#12572298)
Both the National Geographic article (linked above) and the NYT articles (linked in the Nat Geo) article are fairly low quality. No references or citations. Not up to HN's usual front page quality standard.
Re:Australia Is Drifting So Fast GPS Can't Keep Up
by superplussed on Saturday September 24, 2016 @03:53PM
(#12572344)
Also, the animation over-dramatises what is happening and makes it look like Australia is going to slam into Papua New Guinea soon. That's just.. bizarre.
Re:Australia Is Drifting So Fast GPS Can't Keep Up
by Retric on Saturday September 24, 2016 @04:28PM
(#12572503)
First the plate is what's moving not just the landmass. Second it's moving really slowly. They are showing something like a million years of motion, and it's in the wrong direction. https://en.m.wikipedia.org/wiki/Australian_Plate
Re:Australia Is Drifting So Fast GPS Can't Keep Up
by 7952 on Saturday September 24, 2016 @04:19PM
(#12572469)
Before GPS it wasn't terribly useful to know the exact position relative to the entire globe. With a few exceptions (like an ICBM) it is good enough to know location relative to something more local.
Re:Australia Is Drifting So Fast GPS Can't Keep Up
by v768 on Saturday September 24, 2016 @04:27PM
(#12572499)
Reading this article is quite painful due to all the measurements given only in feet & inches, why not give the data in both systems of measurement?
Only 3 countries in the world have not adopted the metric system (Australia did) and this is about GPS and worldwide measurements. Not even NASA uses the imperial units anymore.
>The next adjustment is said to be due by the end of this year, on the order of 4.9 feet.
I don't understand. It moved 4.9 ft since 1994, but was moving more quickly before then? The NYTimes article doesn't seem to clarify this either. Were pre-1994 commercially available maps not based on satellite readings of lat/long?
Th 1994 shift must refer to the adoption of the Geocentric Datum of Australia 1994 (https://en.wikipedia.org/wiki/Geocentric_Datum_of_Australia_... ).
Different datums (models of the shape of Earth) will put the same coordinates at different places. The 656 feet would be the average shift required to reconcile coordinates using the previous datum with coordinates using the new one (which is based on WGS84, the modern global datum).