GPS Says My House is Moving

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House seems to have stabilised today and is staying put :)
No change in GPS set-up or map, so not sure why it was so wild yesterday.
Have only moved +/- 3m the last two hours. Was around 10 times that yesterday :eek:
 
AussieChris said:
Bill Clinton put an end to SA on May 1st 2000, I remember though before it was switched off I used to have dozens of fishing spots marked around the waters of South West Rocks, some days it was so bad it would be 100-200m out and you would have to resort to 3 point positioning, lining up a mountain, a tower and a set of rocks etc
We had a pretty expensive GPS unit on the boat but half the time it might have well been another anchor.

When it was switched off I was able to get within 2 metres of those points without fail, made a huge difference when you were looking for a peak only a few metres wide.
Click to expand...

I do remember that they re-activated SA for the 2nd gulf war in March 2003. I couldn't find the Song Saigon in Darwin Harbour whilst out fishing for that period. I also had to go back to using my old sight lines. I think they only activated it for a month or so.

Cheers

Doug
 
BigWave said:
House seems to have stabilised today and is staying put :)
No change in GPS set-up or map, so not sure why it was so wild yesterday.
Have only moved +/- 3m the last two hours. Was around 10 times that yesterday :eek:
Click to expand...

In the past when that happens within a few days/week you will here on the news that the Americans have been some place or doing something secrete.

Why they do it is crazy because they have high tech stuff that can pick out if someone is watching them within a few miles that they can carry and they also have long range versions fitted to their vehicles so there is no chance of anyone spying on them. so people using Binoculars and scopes can be pin pointed in seconds.
 
A very stable day today, compared to the wild ride of yesterday.
Did not move by more than +/-3.5m.
My house is still very near where it was this morning when I checked.
Leaves me wondering what happened yesterday?
I do know that by 2020 it will have moved roughly 1.7m to the NE (if it's still standing).
 
It's not magnetic variation is it, you know, how we used to have to adjust our maps in the low tech days of compasses and pencils. :D
 
All instruments vary about a mean value - they claim plus or minus 5 m but I find that it is closer to plus or minus 20 m. I suspect that it is not entirely instrument but that satellites dropping in and out would play a role. I once had closer to 50 m but only once. Do you check how many satellites you are locked into at any time - the precsion varies with that and really plays up with too few.
 
Borrowed from an internet article, but pretty well explains....

The GPS satellites are constantly moving in different orbits. Your GPS has been preprogrammed with a description of these orbits, and can internally calculate from that where/when each satellite will be at a particular moment in time.

Each satellite sends out the current time, based on an internal atomic clock. Based on the time, your GPS device then calculates where all GPS satellites should be around the earth.

YOUR coordinates are calculated by simple triangulation using the distance from each GPS satellite* it can receive a signal from in the sky. When the satellites are far apart in the sky from each other, the triangulation accuracy is good. If the satellites are closer to each other in the sky, the triangulation accuracy is poor.

As you stand still, the satellites are whizzing through their orbits in sky, constantly changing their distance and angles to your GPS. Your GPS calculates your position over and over all the time. Every time it recalculates it, the moving satellites change the accuracy of the result, so the triangulation calculation gives a slightly different result each time.

The GPS can tell when it has high accuracy or low accuracy based on the angles between the satellites. Large angle = tighter accuracy, smaller angle = looser accuracy. That's how it gets the +/- ###Feet readout from the GPS.

So if you are at your house, surrounded by other houses, power poles trees etc and all around atmospherics + the number of satellites all travelling at 14,000 kph (approx.), signals drop in, drop out and vary in accuracy. If your GPS only sees 2 or 3 satellites for a time, the signal will lose accuracy, then over time, your house will "go walkabout" :)
 
I think it's set up so that if you have a GPS guided lawn mower you just have to crank it up and sit back with a beer.
 
Or ...... Is it the world moving beneath you

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