Have the Feds reduced GPS accuracy?

[Guest]

The WAAS feature is great...when it locks in, but the WAAS sat's are located above the equator and are mainly used for air navigation. Since we are in a higher latitude, the signal from the WAAS sat's is at a greater angle, hence the lack of signal while against a Southern shore with high banks or trees.

I hav'nt noticed a reduction in accuracy at all. I have my boat unit mounted in my truck right now for ice fishing and I occationally turn it on while driving just for the heck of it. It's amazing how right on the money it is. Cursor is always right on the road and exits and intersections are right on as well.

As far as terrorists using GPS....how accurate do you need to be with an A-Bomb or gas canister?...lol

[LMITOUT]

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The only way that I know of that you can achieve a better accuracy (<30 ft) is with a WAAS GPS receiver. Most of the new ones have it and you must have it enabled on the handset. My Globalmap 100 was pre-WAAS and shows an error of 60' consistantly.

To achieve the best waypoint accuracy, leave the unit sit still in the desired spot as long as possible and then punch in the waypoint. I know that isn't always possible, but thats something I read back when I first got into GPS's.

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I too have the global map 100 (1999-2000)and is there a way to update it? I love the mapping feature and I am too cheap to spend 200-300 for a new one

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Unfortunately, no. There are software updates for the unit but nothing that would add WAAS since that's a different type of receiver.

[ice_shack]

When the dither was shut off it gave the handheld GPS available to the public the ability to be within about 30 meters accurate without WAAS. When it was on it was more like 100 meters. You also have to consider that that 30 meters is actually 60 because it can be 30 in either direction.

WAAS is a great technology but with only 2 birds up there that are WAAS and those are close to the equator it is pretty slim chance you will ever lock on to one.

Where you get your accuracy is the number of birds that you can lock on giving you more reference points. That’s how your unit can tell you that it is capable of being within 3 meters.

Your unit traveling around by itself is not unusual. As the strength of the bird fades in and out its capability to calculate with the same amount of accuracy also fades so it appears as though it is moving.

[muskybuck]

Ice Shack, I think you have those figures multiplied by ten. Anyway, I was using the GPS the last couple of weeks and there is something going on. Has anybody heard anything since this was talked about a couple of weeks ago. I supposed if someone called homeland security and asked them you would be put on a watch list.

[vikingtom]

I see no differece in accuracy. Took me with in 10 feet of me hole the last three weeks.

[Jeremy airjer W]

I plotted a spot on Winnie last weekend. although my gps brought me back to within 10ft of the hole when I downloaded it to my lakemaster software it was about half a mile from where I was actually at. I downloaded it to topo usa to double check and the same thing. This is an older garmin gps 12xl and has always been remarkably accurate. Know I'm starting to wonder!

[irvingdog]

To answer the initail question: NO.

There are far to many businesses that rely on GPS to mess with SA (selective availability. The thing that "scrambles" GPS). Companies that use it to track shipps, trucks, Taxis, and various other industries that are not considered critical to defense would have let out an audible howl that everyone would have heard about by now. Trust me. Something else is messing with your accuracy.

[muskybuck]

To answer the original question, Most probably. Are you thinking that marking a semi driving down a highway with a 50 foot leeway on both sides of the street or a taxi being halfway down a block in a city the same as setting up over the same branch sticking out the NW corner of a crib in the middle of a lake. Thats what I am talking about. I am not talking about setting up somewhere in the middle of Red Lake out in the middle of a basin. I do not think you are talking about the same accuracy I am. Telling me I am on the freeway 12 miles out of Clearwater, Minnesota would not be the accuracy I am talking about. I have been able to set up over that branch for a few years now. This year I can not get within 20- 30 feet of it. I have owned and operated GPS units for eight years now. I know what they were like at first when you could get within 15 feet of the branch. I know what they were like after the restrictions were removed when I went right over the branch and I know what it is like now when the GPS will bounce back and forth with up to 30-40 feet differences.

[irvingdog]

Well, since you posed the question, then choose to answer it, I cannot help you. I can tell you that Geocaching.com has seen no drop in success rate at finding small, and sometimes ultra small (film canister sized) items hidden in very covert locations. And this is averaged out over tens of thousands of users.

BTW, this isn't my first barn dance either. I've been using and selling GPSr's for a decade or so as well.

[muskybuck]

So you think I am making the differences in accuracy up? You seem to be an expert. It seems like you know for sure. Tell me why my accuracy is thirty feet off this year. Not on just one unit but many. What do you think of the accuracy differences over the years I described in the previous post. Just that I'm full of it? My son went out with his unit today and was close to 50 feet off.

[irvingdog]

I honestly didn't attempt to engage in an arguement with you in either post. I bow to your expertise.

[troutstix]

i have had a gps for 6 or 7 years, i use them all the time- this year quite a bit more than usual, i have not noticed any changes in accuracy at all- with any of the gpsr's i have.

[Jeremy airjer W]

Theres a huge difference between Geocaching (pretty fun, I'd reccomend trying it if you haven't) and finding a hole. I can see all the tree landscape and whatever else when geocaching if my gps gets me to within 20-30 feet I just start looking. Eventually I'll find it. If I'm looking for a hole obviously I can't see anything and rely heavily on the accuracy of the gps to get me within the 10ft area so I can more easily narrow the search with the auger, vex, & experience.

[ice_shack]

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Ice Shack, I think you have those figures multiplied by ten.

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No, those numbers a quite accurate. If you would like references to the info I would be happy to provide it. Then again you obviously have the internet, try a Google search and read a little.

[irvingdog]

The acception being that a huge percentage of cachers are accuracy nuts, and if co-ordinates differ, they post such findings. I'm not saying that finding the only fallen log in the woods and finding a sunken hump are the same thing. I'm saying that civilian usage of GPS is intrenched in our comerce and entertainment. If the government had messed with S.A. it would have been brought to light by now by people with vested interests in it being reliable and accurate.

[McGurk]

Here's another little known nugget for you conspiracy buffs... I have a reliable source that says that the squads in Bloomington have had issues with their GPS recievers in their cars bumping them INTENTIONALLY from the area around the Mall of America to an area in the middle of of Hyland Park in the 3 Rivers Park district which is un-inhabited.

When driving to the MOA the coords match up good to their location up to about 1 block away and then tells them they are in the middle of the park! It's like that until they drive past and then locks them back on to the right spot. This is in multiple cars and is has just been accepted as normal. Intentional, perhaps, or just poor signal lock?

Have fun with that! McGurk

[computerboy]

Okay McGurk, now you’ve got me really intrigued. So much so that I did some research and may have found an explanation as to why your sources on the force have seen such odd behavior on their GPS receivers when driving by the Mall of America. Apparently the military has developed dithering capability for a specific location (a.k.a. “Regional Denial”). Regional Denial gives them the capability of altering the signals of a specific area, as opposed to globally altering the signals with Selective Availability. The Mall of America would most certainly be considered a “location of interest” as it relates to national security. If Regional Denial is being used domestically, the signals would almost certainly be altered for the Mall of America during elevated threat levels.

Hey muskybuck, does that body of water you’re on happen to be near a municipal water supply, power plant, or any other “location of interest”? While your issue may have nothing to do with Regional Denial (assuming it’s even being used domestically), it would be interesting to know if other FM'ers see the same behavior when driving past the Mall. Very interesting stuff McGurk.

Below are some excerpts of what I found:

It is not the intent of the US to ever use SA on the civil signal again. To ensure that potential adversaries do not use GPS, the military is dedicated to the development and deployment of regional denial capabilities in lieu of global degradation through SA.

"We have demonstrated the ability to selectively deny GPS signals on a regional basis, particularly ... when our national security is threatened," said Lt. Jeremy Eggers, a spokesman at Schriever Air Force Base in Colorado.

[McGurk]

Freakin' sweet, Neil.. er.. computerboy. For our own safety, I guess. I just hope my portable isn't a international target; signal seems good where I go.

[McGurk]

So, an update to my little nugget... It turns out the automatic relocation was totally a mistake, due to human error. It was just an extreme coincidence that it was the MOA to an empty park. The system has the city divided into "blocks" (not city blocks) where if your vehicle has certain coord it puts you in a certain block. When you move and reach the edge of the coord values for your block you get placed into the next block with corresponding coord values. So the mistake was in assigning the coords to the correct block in that area, and was just related to their system. The coords were always good.

I also asked about the ability to intentionally offset placement around important structures, and he said that there isn't a way to do that from the satellites that are orbitting. But if you had a transmitter on the ground at the site sending the same type but incorrect algorithms to intentionally offset your receivers it could work. Your receiver would see a lock but the incorrect info received from it would throw off your location. Seem plausible? Maybe you have a rich enemy with too much time on his hands, muskybuck Good Luck! McGurk

[ice_shack]

It's very plausable, in fact it's common practice. Not to through you off but to have a ground transmitter. These are know as "beacons" and the are used for applications such as civil engineering. When doing field surveys for utilities and such where you need the extra accuracy these beacons are placed at known coordinates. Doing so give the reciever more and better reference points and can get them down to a reliable accuracy of 1/2 meter. Not just for Lat and Long but for altitude as well.

[McGurk]

I agree with the additional transmitters to tighten up accuracy, but to send a signal to intentionally throw it off? I suppose if you enter the beacon's reference point with incorrect coords from where it actually is, the result would be poorer accuracy. If you had multiple Sat. locks agreeing and 1 ground beacon telling you otherwise, would the unit disregard it or factor that signal in? And could it actually tell your receiver that you are in a completely different area with a tight accuracy?

[ice_shack]

I don't know for a fact but I would venture to say that the cheaper units <$1000 don't have the capability to ignore a ref point. I know that the expensive ones do. As far a one beacon throwing you of any great distance is highly unlikely. I'm not to sure they even have the capability to be told they aren't where they think they are right off the shelf. Someone would have to hack into the software and reprogram it to accomplish that.

[Ice9]

Just read the entire thread...excellent work, gentlemen. One question of clarification. Do the different formats have different accuracy? Somebody suggested this. If so, why?

ice

[computerboy]

I was this close to driving out to Bloomington last night to test out our latest theory in the ongoing saga of muskybuck's GPS issues. I'm glad I didn't after reading your latest post. I'm still intruiged by the whole regional denial thing though. When SA was still on, you would see the exact same behavior muskybuck is seeing (i.e. traveling cursor when standing still). Perhaps the feds have been testing some regional denial around muskybuck's area? Oh well...maybe we'll never know. Or better yet, maybe "they" don't want us to know....(and the saga continues)

By the way, it's good to know you're a "family guy" McGurk!