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Tamarmole
50.2% (Neutral)
Newbie Topic Starter

10 years ago

I was out plotting mining features today (7th May) in East Cornwall. My little GPS unit did not seem as accurate as usual (12m - 15m rather than 5m - 9m). Have they (whoever they are) turned the accuracy down because it is election day or am I being paranoid?

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Morlock
50.2% (Neutral)
Newbie

10 years ago

When the NATO summit was on in Newport a lot of kit other than drones/quadcopters were jammed, same in Brum during the Tory conference.

rufenig
50.2% (Neutral)
Newbie

10 years ago

The "downgrading" was called selective avaliability.
"They" have stated that it will remain off.

Federal Aviation Administration.
On May 1, 2000, President Clinton signed an order ending SA as part of an on-going effort to make GPS more attractive to civil and commercial users worldwide. Now, GPS is accurate within 40 feet, or much better. Military GPS is even more precise and has a margin of error of only a few centimeters.

The end of Selective Availability was a major turning point that has helped GPS to become a global utility, now being used around the world in many different applications.

After the attacks of September 11th, the industry buzzed over the possibility of a return to SA. However, on Sept. 17, 2001, the Interagency GPS Executive Board (IGEB), which governed the GPS system at that time, announced the United States has no intent to ever use Selective Availability again.

However jamming of GPS signals has become much more common, prehaps you were on the edge of one.
You could submit a "freedom of information " request, but I would not expect an answer!:(

royfellows
50.2% (Neutral)
Newbie

10 years ago

We wouldn't want the head of the Raving Looney Party assassinated by a terrorist cruise missile would we.

Make a good plot for a spoof James Bond film.

My avatar is a poor likeness.

Morlock
50.2% (Neutral)
Newbie

10 years ago

They also loose accuracy in certain steep/narrow valleys, (if you can get a signal at all).

Tamarmole
50.2% (Neutral)
Newbie Topic Starter

10 years ago

"Morlock" wrote:
They also loose accuracy in certain steep/narrow valleys, (if you can get a signal at all).

I was surveying in a narrow wooded valley (Wheal Mexico). However I had been surveying further up in the same valley a couple of weeks earlier (Wheal Brothers, West Prince of Wales) with better results/ accuracy.

lozz
50.2% (Neutral)
Newbie

10 years ago

Might be multipath error.

There was an X2 solar flare but that was yesterday not today.

Lozz.

rufenig
50.2% (Neutral)
Newbie

10 years ago

😮 You all know its not a natural phenomina!
It's the men in black! 😮

davel
50.2% (Neutral)
Newbie

10 years ago

I've been using a GPS (Garmin 64s) this afternoon to get to features I located on Magic Map (http://magic.defra.gov.uk/). It's been spot on - proximity alarm sounded within 2m of a shaft and while standing in a cutting very close to the entrance to a level, both on a north-west facing wooded hillside - so it seems OK to me.

Dave

Tamarmole
50.2% (Neutral)
Newbie Topic Starter

10 years ago

#10

We had call me Dave and Milliband down in Cornwall yesterday which might have something to do with it.

royfellows
50.2% (Neutral)
Newbie

10 years ago

#11

They would ****** anything up

My avatar is a poor likeness.

ebgb
50.2% (Neutral)
Newbie

10 years ago

#12

selective accuracy still gets turned on and off regularly

it was turned off recently for the joint warrior NATO excercises off the west coast of scotland, with some localised jamming too

http://bf494.co.uk

ChrisB Underworld
50.2% (Neutral)
Newbie

10 years ago

#13

The zone of error in your GPS position used to be displayed on some GPS units, my old Garmin III plus used to have a page devoted to it, trees/steep ravines does interfere with the signal from the satellite, can be 1m to 400m at times, when bad, stand still and you're position moves on the GPS, that's why measuring distance, time, pacing with a 1:25000 map will always help, my satmap unit is more accurate, march of progress with electronics, you could get a DGPS

remoteneeded
50.2% (Neutral)
Newbie

10 years ago

#14

I find the accuracy of my units varies with the weather. If there's lots of rain clouds around then the accuracy gets worse. Also if I'm in a wooded area and it has rained the day before then I find my unit can be all over the place. I've always assumed this was due to the damp leaves blocking the weak signal from the satellites.

EDIT: The internet says that I'm probably wrong!
http://gpsinformation.net/gpsclouds.htm

lozz
50.2% (Neutral)
Newbie

10 years ago

#15

"remoteneeded" wrote:
I find the accuracy of my units varies with the weather. If there's lots of rain clouds around then the accuracy gets worse. Also if I'm in a wooded area and it has rained the day before then I find my unit can be all over the place. I've always assumed this was due to the damp leaves blocking the weak signal from the satellites.

EDIT: The internet says that I'm probably wrong!
http://gpsinformation.net/gpsclouds.htm

The statements in that link are basically correct but can be misleading, water vapour can and will attenuate the signal at the frequencies concerned, it says that but signal attenuation though isn't really a factor when making time related measurements, what matters in that case is just that, time delay, electromagnetic radiation travels at the speed of light but only in a vacuum, introduce something into that vacuum and the wave will travel slower, the biggest effect so far as earth is concerned can take place in the ionosphere, conditions regarding wave propagation through that part of the atmosphere can vary by quite a bit, the prime mover for that is the Sun and events that can take place on the Sun, these effects are taken into consideration in a virtually real time situation but the severity of these effects can sometimes be very much localized in relative terms.

Lozz.