GPSs are all wrong!

[DiscoMick]

Yep, our GPS coordinates are out by up to 1.5 metres, but it's not the GPS unit's fault - its Australia's.
Our continent is moving north at 7cm a year (making us the fastest-moving continent - Australia leads the world again) and our longitude and latitude haven't been updated for a while, so our GPS units are out by 1.5 metres.
Australia's latitude and longitude coordinates out by more than 1.5 metres, scientists say - ABC News (Australian Broadcasting Corporation) (http://www.abc.net.au/news/2016-07-28/aust-latitude-longitude-coordinates-out-by-1-5m-scientists/7666858)
So, next time your GPS gives you a bum steer, you know why.

[vnx205]

I suppose that could be a problem if you use GPS to locate the position of a sewer pipe before doing some excavation.:-)

[sheerluck]

Well, I wanted a holiday up near the equator, so if I wait another 435000 years or so, I can float there without having to pay. Woohoo! Cheap holiday!

Saying that, there is a flaw in the plan, I just can't quite put my finger on it. :confused:

[67hardtop]

No wonder i couldnt find my driveway. I kept running over the neighbours letterbox instead. Bloody gps 😆😆

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

[DiscoMick]

Yes, situations like finding sewers could be a problem.
Amusingly, we discovered the local council has absolutely no records of the septic system at our house at Maleny when we bought it, no idea at all.
I wonder if this affects plans of property boundaries. Our neighbor in Brisbane discovered the local council plans were wrong and his sewer line was actually on his neighbour's property, not his. That meant he had to change his house renovation and extension plans and put the new main bedroom at the rear rather than the front of the property, because he couldn't build over the sewer line where it came onto his property from his neighbour's.
So it can be a big deal.
I wonder what other problems this has caused. For example, does this mean that aircraft GPS system are wrong?

[JDNSW]

Yes, situations like finding sewers could be a problem.
Amusingly, we discovered the local council has absolutely no records of the septic system at our house at Maleny when we bought it, no idea at all.
I wonder if this affects plans of property boundaries. Our neighbor in Brisbane discovered the local council plans were wrong and his sewer line was actually on his neighbour's property, not his. That meant he had to change his house renovation and extension plans and put the new main bedroom at the rear rather than the front of the property, because he couldn't build over the sewer line where it came onto his property from his neighbour's.
So it can be a big deal.
I wonder what other problems this has caused. For example, does this mean that aircraft GPS system are wrong?

While it is interesting that the discrepancy is that large, it should be pointed out that very few maps even pretend to be that accurate - and cadastral (i.e. property boundaries) are defined relative to the trigonometrical grid, so that any competent surveyor would tie his GPS position to a permanent survey mark nearby.

The position of the sewer pipe will have had nothing to do with GPS - it probably was not installed using GPS or any other form of surveying!

As for aviation - enroute separation is measured in nautical miles, not metres, and even in a precision approach and landing, a landing would be considered 'perfect' if the nosewheel ws that close to the centreline!

As for services maps - several years ago I 'dialed before I dug', when I was rebuilding a fence I knew crossed the phone line. The map I was supplied showed the phone line position around a kilometre from its actual location!

John

[Avion8]

That explains why my Garmin LMT lane departure warning was continually going off, so much so that I have deactivated it.

[JDNSW]

Simply means the map is inaccurate - and the movement of Australia is a very minor inaccuracy compared to other errors!

John

[DiscoMick]

That explains why my Garmin LMT lane departure warning was continually going off, so much so that I have deactivated it.
That's interesting. If the GPS location was 1.5 metres off, could that cause a lane departure warning to go off?

[Avion8]

That's interesting. If the GPS location was 1.5 metres off, could that cause a lane departure warning to go off?

I guess so if it thinks you are 1.5 mtrs closer to the left hand side of the road. Luckily most of our main roads here have the ribbed white line, which you can definitely hear if departing the lane, usually when those great big wide loads are coming the other way with a house, or haul pac.

[sheerluck]

....Our continent is moving north at 7cm a year (making us the fastest-moving continent - Australia leads the world again)...

If there's an Ashes version of tectonic plate movements, then we would beat the UK at least. The Eurasian plate is only moving south at between 7 and 14mm per year. :D

Last one to the equator buys the beer!

But that poses an interesting question, all longitudes are measured from the Greenwich Meridian (or as near as dammit), so if the Greenwich Meridian is moving as well, we don't stand a chance in ever being correct.

[Tombie]

GPS - as used by civilian navigation systems has an accuracy of ~10mtrs...

If you want better you need DGPS...

[Tombie]

I guess so if it thinks you are 1.5 mtrs closer to the left hand side of the road. Luckily most of our main roads here have the ribbed white line, which you can definitely hear if departing the lane, usually when those great big wide loads are coming the other way with a house, or haul pac.



I'd be shocked if there is still a Haul Pac in operation anymore... Cat or Komatsu perhaps [emoji106]

[PhilipA]

Bit of a joke when Garmin maps show the road going into a reservoir south of Emerald when the road across the dam wall has been there for about 10-15 years or so.
In fact many of the Garmin maps of smaller roads eg the Plenty Highway, show you hundreds of metres off the road.LOL

Regards Philip A

[DiscoMick]

http://mobile.abc.net.au/news/2016-07-28/why-it-matters-that-australias-coordinates-are-moving/7668014
Sent from my SM-G900I using AULRO mobile app
Apparently driverless cars need accurate GPS.

[Bushie]

Bit of a joke when Garmin maps show the road going into a reservoir south of Emerald when the road across the dam wall has been there for about 10-15 years or so.
In fact many of the Garmin maps of smaller roads eg the Plenty Highway, show you hundreds of metres off the road.LOL

Regards Philip A

Last time I drove the Plenty Highway (30+ years ago) it was at least 200 metres wide and maybe 10 lanes.
Well the bulldust bits were.


Martyn

[Homestar]

I'd be shocked if there is still a Haul Pac in operation anymore... Cat or Komatsu perhaps [emoji106]

There's still a few around - one is still running around a quarry not far from here. The owner keeps it on for sentimental reasons. :D. It runs its original 1710 cummins V12 - smokey old beast but refuses to go to God.

He used to run quite a few, most have gone to scrap and there's a couple more parked up near the workshop for spares.

[Narangga]

Turns out my mum was right - what goes around comes around (eventually) :o

[ozeraser]

Technobabble warning..

The GPS wont be incorrect, GPS is just time from a known satellite point in the sky. The way the map shows and extrapolates lat and longitude would be incorrect. I would guess that when they make a map they use three known points (like surveyors use) like Far West,East,North and South then match those points on their map, and skew the tiny shift in maps so that the lat and long locations don't move.

But if were talking cool stuff, how would you go with fault creep, In San Francisco they have creeps through the middle of the town.

The Town That Creep Built – BLDGBLOG (http://www.bldgblog.com/2015/04/the-town-that-creep-built/)
Hayward Fault:? Residential Area North of Downtown Hayward (http://www.geologyfieldtrips.com/haywardresidential.htm)

[theresanothersteve]

From my experience GPS and satellite navigation, even in the same device, uses different systems.

I'm guessing the sat nav uses GPS to pinpoint a location and then apply it to the nearest road. Where I turn off for home the two roads run alongside one another, being separated by 10 metres after a hundred metres or so (although there is a steep gully between the roads) before finally branching away.

For the first hundred metres or so it is common for the display to show the car jumping from one road to t'other as it tries to workout which road I'm on.

[ramblingboy42]

I think that's fairly normal.....even aircraft systems have problems 10-20 feet off the ground, the display being uncertain if the aeroplane is on the ground or above it.

[DiscoMick]

I seem to remember reading that the public GPS signal has an accuracy of, I think, 0.5 metres, while the military version is more accurate, but I could be wrong on the details.

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[theresanothersteve]

More technobabble...

The GPS satellite broadcasts a time signal and a thing known as an almanac, basically a file telling the receiver where the GPS satellites are going to be for the next (I think) 3 months.

The receiver reads the time signal, compares it with its own time and calculates how far away the satellite is by the difference in time. To be accurate the system needs to be reading from 4 satellites, preferably spaced across the sky.

The fourth satellite is used to calculate elevation, so if there are only 3 that can be used the GPS guesses the elevation based on the last good fix. This works on a plain, or on water, but is not much good in hilly terrain. If you are in this situation, and can download the breadcrumbs and overlay them on a map the calculated position gets less and less precise rather quickly.

When GPS first became available the US decreed that civilian units had an inbuilt error, to prevent consumer GPS being used to target weapons. The error (which was random) was from the satellite. This random error, however, was turned off by the Clinton administration.

[jx2mad]

Driving out to Longreach recently and my gps showed the rail line on the southern side of the road when it was on the northern side. Then there was a crossing which never existed and the rail changed sides.At least it was showing on the correct side.

[hodgo]

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

[Tombie]

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming

DO you think some one should tell the greenies about before its toooo late.?



Hodgo



What are you smoking? [emoji41]

[ramblingboy42]

won't an extra hour of daylight warm the planet up more?

[ramblingboy42]

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

just change the time on your gps....it wont know.

[DiscoMick]

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

Move to Queensland. We don't do unnatural stuff like tinker with the time up here.

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[JDNSW]

Driving out to Longreach recently and my gps showed the rail line on the southern side of the road when it was on the northern side. Then there was a crossing which never existed and the rail changed sides.At least it was showing on the correct side.

That is simply a problem with the map. The actual GPS system does not know about maps - it just positions the receiver relative to a geometric spheroid that approximates MSL. Your receiver then correlates this to a map it has stored - and every map has errors and inaccuracies and is not up to date - just some more than others.

John

[austastar]

Hi, my Sygig app has 'snap to track', and will sometimes have a leader line from the arrow ( position) to where it thinks I should be on the road.
Ozi just shows me the map is wrong.
Cheers
Sent from my GT-N5110 using AULRO mobile app

[Tombie]

If your Ozi is out it's more likely poor calibration of the map than the map itself.

[austastar]

If your Ozi is out it's more likely poor calibration of the map than the map itself.

Hi,
Ozi is generally spot on the road on most maps, so they are ok with calibration.
I catch the odd road in the wrong place though, often not by much, but a corner has been cut or the road re-aligned.
Cheers

[ramblingboy42]

ded reckoning , map to ground , **** the gps.

[AK83]

Hi,
Ozi is generally spot on the road on most maps, so they are ok with calibration.
I catch the odd road in the wrong place though, often not by much, but a corner has been cut or the road re-aligned.
Cheers

I've had to recalibrate many hundreds of Vic 25K topos manually .. took forever to do, over the course of a few months.
And you're right on about some of the realigned roads .. depending on the dates of the maps, many roads/tracks and obstructions change over the years.
You can update that info using the desktop version of Ozi too.


ded reckoning , map to ground , **** the gps.
This is how they got the Vic-SA border so wrong! .. to the benefit of western Victorians of course :thumbsup:
That's why there's a misalignment of the SA border with Vic compared to the border line north of the Murray River in NSW.
I think the land lost in SA amounts to about 1/2 million sq miles or something.

.. good ol dead reckoning ... it made Victoria 'The Place to be'(or so say the number plates!) :p

[theresanothersteve]

The first GPS course I attended, run by the army for the fire service, was quite interesting. It was GPS, not SatNav, back then if there were any maps on a GPS they were quite crude and navigation was plotted using waypoints...

The instructor, a major from the artillery, said they have found there are a lot of errors in paper maps that didn't realise until the army started playing with GPS. It would appear that as a target get further and further from your location, the map based calculations don't line up with the GPS based calculations. For example, the bearing and distance to a target reads differently from paper when compared to the GPS. The further away, the more likely a bigger error occurs.