GPS Says My House is Moving

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BigWave

BigWave

Big Wave
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Either I've the "wobbly boot" on or my GPS is screwing with me.
I geo-referenced a GeoVic map of my VIC suburb and loaded it to QGIS (on my PC - Windows 10). With an external GPS unit connected to a USB port, I then drove to the local IGA for some refreshments. With GPS tracking points turned on, it proved to be pretty accurate on the drive - closely following the road (so geo-referencing was all good)
1515224500_iga_drive.jpg

When home I left it running for a few more hours and watched my reported house location wandering drunkenly over the map at higher resolution. One day my house may even be on my lovely neighbour's property, But I'd likely be had for stalking :eek:
You can see where I reversed out of my drive onto the road.
1515224836_house_movingjpg.jpg

Measured discrepancies are +/- 22m in latitude and +/- 25min longitude.
Is this usual for GPS? Even had my house velocity as high as 3kmph at some point, but I never felt the acceleration.
 
BW probably due to signal changes that your device is receiving .............. will most likely be worse if unit is indoors or when only weak signal. Moving satellites as above has a play in this . The unit your using will also probably magnify it more so compared to a good stand alone GPS :)
 
1. The U.S. has sneakily switched S.A. back on :N:
2. There are timing errors in your GPS when stationary, not noticed during driving
3. Your house really is moving :D
 
BigWave said:
Either I've the "wobbly boot" on or my GPS is screwing with me.
I geo-referenced a GeoVic map of my VIC suburb and loaded it to QGIS (on my PC - Windows 10). With an external GPS unit connected to a USB port, I then drove to the local IGA for some refreshments. With GPS tracking points turned on, it proved to be pretty accurate on the drive - closely following the road (so geo-referencing was all good)
https://www.prospectingaustralia.com/forum/img/member-images/6786/1515224500_iga_drive.jpg
When home I left it running for a few more hours and watched my reported house location wandering drunkenly over the map at higher resolution. One day my house may even be on my lovely neighbour's property, But I'd likely be had for stalking :eek:
You can see where I reversed out of my drive onto the road.
https://www.prospectingaustralia.com/forum/img/member-images/6786/1515224836_house_movingjpg.jpg
Measured discrepancies are +/- 22m in latitude and +/- 25min longitude.
Is this usual for GPS? Even had my house velocity as high as 3kmph at some point, but I never felt the acceleration.
Click to expand...

PDOP variance old c0ck, related to number of satellites visible for fix and their height above the horizon. Affects legacy GPS units.

IS your a GNSS receiver?
 
Yep looks like it, Now that's what you call a Mobile Home, Lol, :lol: :lol: :lol: :lol:

When the US Gov are doing one of their Sorties they mess with the GPS system and once it is over they switch it back, Most of the time mine is within 3 to 5 feet but if you stand still all GPS's will hone in and be within a foot or less, my GPS will even lock on to the SAT's when it is indoors.
 
Yep US Gov can change it to vary as much as they want. In the case of a nuclear strike they could make the missiles out by a thousand miles (but if it was me I'd change the configuration to make my enemies house look like it was me lol) ]:D
 
Ridge Runner said:
Yep looks like it, Now that's what you call a Mobile Home, Lol, :lol: :lol: :lol: :lol:

When the US Gov are doing one of their Sorties they mess with the GPS system and once it is over they switch it back, Most of the time mine is within 3 to 5 feet but if you stand still all GPS's will hone in and be within a foot or less, my GPS will even lock on to the SAT's when it is indoors.
Click to expand...

That's called, well, what 'used' to be called "selective availability" and its when the DoD mess with the C/A code. I may be wrong but I think it means messing with the time signal from the satellites. Also ALL GPS receivers stop functioning when their position changes by more than a certain speed threshold that negates unauthorised inter continental missiles being guided by the GPS system.

Basically anyone surveying GPS baselines during the first Iraqi invasion by the U.S. was Sheet out of luck due to selective availability. No amount of post processing or least squares adjustment was going to give you anything workable!

It's been many years since I had anything indirectly to do with the industry and I assume things have changed dramatically since then. Would appreciate any corrections to my line of thinking if I'm in error.
 
They use to off set them by about 70 to 100 feet now I don't think they bother anymore, I checked mine during the last Gulf war and it was always reading the same as it does now, They do warn you about them doing that in the manual but every time they were up to no good I checked mine out and it was always accurate,
 
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.
 
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...

Thanks mate, As I said its been quite a while since I turned on an industry grade GPS receiver. I still have a couple of Leicas about the place somewhere!
 
I used to design power lines 4 country energy in nsw 1 is num of satellites 2 terrain that u r around heat haze etc and the big 1 is the gov and the yanks move them 4 num reasons enemy ,realign them 4 the day we had a nightmare with when thay when t taping on door in Iraq ,Flatlander
 

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