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Signal/satellite Inaccuracy


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Don't know IF this has been addressed before . . . but, is it just the Carolina (USA)area OR is everyone having the difficulty of readings often-to-always being up to 25 feet off target.

 

It is getting really hard to find those micros-in-the-woods with a poor signal, tree cover and no hints even though I simply love these things and wish there were more of them.

 

Wonder if the earthquake/tsunami event in the Indian Ocean twisted the earth a bit in relation to the satellite orbits - anyone know of this possibility or sharing the concern?

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I thought the earthquakes made the earth slightly smaller and therefore increased the speed of the spin?

 

Either way, I also doubt that its causing an epe problem. It will only make us crash into the sun faster. :P

 

I haven't had epe probs lately. Without WAAS, I consistently get an epe of about 13 feet. With WAAS, 8 is typical, 6 occasionally.

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I heard somewhere (from some source) that the Earth's spin is constantly slowing. Is that urban legend?

 

And if it isn't, do the satellites take that into account? :P

 

I figure if anyone knows the answer, fizzymagic would.

Yes, the Earth is spiining gradually slower...at an abominably minute rate of decrease.

 

Yes, this is actually taken into consideration. rather, instead of taking this one factor into consideration, the satelites make very minute course corrections from time to time to accomoadate all of the factors and forces in play.

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I thought the earthquakes made the earth slightly smaller and therefore increased the speed of the spin?

 

Either way, I also doubt that its causing an epe problem. It will only make us crash into the sun faster. :P

 

I haven't had epe probs lately. Without WAAS, I consistently get an epe of about 13 feet. With WAAS, 8 is typical, 6 occasionally.

First, earthquakes don't change the mass of the Earth. The the extrememly large volcanic eruptions which spew megatons of ash into the atmosphere have very little of it escaping into space. The vast majority settles into the atmosphere and most of that goes back to the Earth.

 

Secondly, if Earthquakes did cause Earth to lose mass, we would travel further from the Sun, not closer.

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Don't know IF this has been addressed before . . . but, is it just the Carolina (USA)area OR is everyone having the difficulty of readings often-to-always being up to 25 feet off target.

 

It is getting really hard to find those micros-in-the-woods with a poor signal, tree cover and no hints even though I simply love these things and wish there were more of them.

You have to, also, take into consideration that not every set of coords you print out or download are going to be dead-on every time, either. This is dependent not only on your device and skills, but also on the device and skills of the person who placed the cache, the surrounding environment and its physical features which affects reflectivity and absorbtion of radio waves, and many other things.

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However, the difference something like 3 billionth of a second per day - not enough to make micros any harder to find. B)

It seems to me that this should actually make it EASIER to find those micros-in-the-woods. I'm always hoping for more time, to find the d*mn thing before the light fades.

 

Shouldn't the earth slowing down give me more time to look? :P:PB)B)

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I heard somewhere (from some source) that the Earth's spin is constantly slowing. Is that urban legend?

 

And if it isn't, do the satellites take that into account?  :P

 

I figure if anyone knows the answer, fizzymagic would.

Actually, what is amusing is that for the last few years, the Earth's spin has been speeding up.

 

It's funny, because there are mechanisms for inserting leap seconds to correct for slowing down, but none to remove seconds for speeding up. Of course, the speedup is temporary, a glitch in the secular slowdown.

 

More info here .

 

GPS time is off from UTC by about 4 seconds now as a result of leap seconds having been added since the GPS system was started (the GPS system does not use leap seconds).

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First, earthquakes don't change the mass of the Earth.  BLAH BLAH BLAH

Umm, did anyone mention that the earth was losing mass? :P

"I thought the earthquakes made the earth slightly smaller and therefore increased the speed of the spin?"

 

Ok. By "smaller," you actually meant _____.

 

?!!?

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Less volume without less mass means the material contained within the object was compressed. Earth does not compress during an earthquake (not for a prolonged period of time, anyway...mere moments).

 

If the Earth becomes smaller without the material being compressed, it had to have lost some of its mass.

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...If the Earth becomes smaller without the material being compressed, it had to have lost some of its mass.

Imagine a stack of bowls so the first is right-side up and the second is upside-down. Each additional one is reversed until ten are stacked. Now imagine identical bowls stacked all right-side up. Each pile has identical mass, but the first is clearly bigger.

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Mind you, I am no geologist, but my understanding is the plates were pressed against each other with ever increasing force. The earthquake was caused by one plate sliding under the other, changing the earth's shape and size.

All true...except for the very last word.

 

Two plates rub, fracture, reverbrate...

 

Different shapes when its all over, but the same amount of material.

 

If you take a pound of dry spaghetti and crumble it up, you still have a pound of dry sphaghetti.

 

:P

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...If the Earth becomes smaller without the material being compressed, it had to have lost some of its mass.

Imagine a stack of bowls so the first is right-side up and the second is upside-down. Each additional one is reversed until ten are stacked. Now imagine identical bowls stacked all right-side up. Each pile has identical mass, but the first is clearly bigger.

I see what you're saying with the bowls, however, the size, mass and volume of the actual bowls would remain the same, regardless, the space occupied by the concave side of the bowl, of course, varies accordingly...but that's not part of the actual bowl, is it?!

 

Now if you are using the two bowls facing each other as an example of the earth, then I would have to point out what you already know...the Earth is not hollow.

 

:P

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If you take a pound of dry spaghetti and crumble it up, you still have a pound of dry sphaghetti.

I never suggested that there was any change in mass (or amount of material).

 

If you take a pound of dry lumaconi and crumble them up, you still have a pound of material, but it will be a smaller pile. You will also be unable to make a tasty farciti. :P

Edited by sbell111
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... Now if you are using the two bowls facing each other as an example of the earth, then I would have to point out what you already know...the Earth is not hollow.

Nor is it a solid, unyielding mass.

Unyielding...no. Nor is it (discernably) compressable.

 

Same volume. Same mass. Same temperature = Same size.

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Seriously, are you just arguing to argue?

I'm just having a discussion. I enjoy discussing things. Sometime I learn something new.

 

I'm not trying to annoy you. I'm just talking about something and expressing my view.

 

I happen to think I'm right.

 

If I'm not, someone please enlighten me.

 

If I'm bothering anyone...I apologize. That wasn't my intent.

 

:P

 

:P

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Same volume.  Same mass. Same temperature = Same size.

Yes, but it is not always at the same temperature. The thickness of the plates change. As they slide under one another they can remelt (subduction).

 

Certainly, you agree that the shape of the Earth changed due to the earthquake. It is widely reported (and discussed in the GC forums that the Earth is more oblate than before. Is it longer? If you believe so, why?

 

edit: typo

Edited by sbell111
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Is anybody else hungry, or is it just me?

 

Do I have more time to eat, or less?

 

And I need coordinates for a good Italian restaurant...

If you ever come to Addison,TX (NE of DFW) I think they they have about the largest concentration of restaraunts per capita in North Texas. There are hundreds of restaraunts and a bunch of'em are Mom and Pop Italian restaraunts. Good Eatin'!

 

They even have this one place that serves big slabs of meat skewered on swords!

 

Then, there's the magic Time machine. Your server can be anyone from the past or even a fictional character. Its kinda scary the first time through.

 

:P

 

:P

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Same volume.  Same mass. Same temperature = Same size.

Yes, but it is not always at the same temperature. The thickness of the plates change. As they slide under one another they can remelt (subduction).

 

Certainly, you agree that the shape of the Earth changed due to the earthquake. It is widely reported (and discussed in the GC forums that the Earth is more oblate than before. Is it longer? If you believe so, why?

 

edit: typo

Hey, got some help on your side! Alright.

 

Well, there is usually more than one factor involved but some of it may be the aforementioned speed of the spinning Earth, the quailty and quantity of the atmosphere and the friction created thereby, the position and mass of nearby planets, stars and systems which produce a gravitational pull, The position of the (as you mentioned) less-dense liquids and more-dense solids through out the mantle, and of the condition of the core itself. All of these may be negligible factors as far as we are concerned, however, they all contribute and I am sure there are other factors I would never imagine.

 

Concerning the temperature...I am considering the planet as a whole. Certain portions of the planet may warm and cool (a redistribution of energy and changes of state of energy) but the collective amount as a whole is generally the same from day to day, earthquakes included.

 

Geology Rocks! (Pun intended.)

 

:P

Edited by tabulator32
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Hey all,

 

I used to be a GPS payload analyst in the 2 SOPS, the Air Force unit that operates the GPS constellation. In a nutshell, the navigation data uploaded to the satellites daily does indeed account for variance in Earth rotation.

 

This variance is irregular, and impossible to predict with complete accuracy, as it does arise from sources such as wind, atmospheric friction, etc. But NGA provides observation of UT-UT1 to the 2 SOPS each week. These observations are used to generate predictions of rotational variance and polar wander. These predictions are in turn used in the coordinate transformation that takes place each time a navigation upload is generated.

 

The tsunami did indeed have an effect on Earth rotation, but the effect was minute, and would already be absorbed into GPS predictions. If the error WAS ever big enough for us to see, it would have occurred in the time between when the tsunami occured and the satellites were uploaded with a fresh navigation message. In all likelihood, only someone heavily post-processing GPS data would notice any perturbation.

 

Peace,

TeamRJJO

Edited by TeamRJJO
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Don't know IF this has been addressed before . . . but, is it just the Carolina (USA)area OR is everyone having the difficulty of readings often-to-always being up to 25 feet off target.

 

It is getting really hard to find those micros-in-the-woods with a poor signal, tree cover and no hints even though I simply love these things and wish there were more of them.

 

Wonder if the earthquake/tsunami event in the Indian Ocean twisted the earth a bit in relation to the satellite orbits - anyone know of this possibility or sharing the concern?

IT is not the satellites it is the US Goverment they dont want you to know where you are so they rig the satellites to give you false coordinates. I mean look at the military GPSr.......

 

Okay get real 20 to 30 feet is NORMAL. Shees does anyone read the forums does anyone read there owners manual??????????????

 

cheers

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Accuracy from me to the cache, or what my GPS says?

I live in wesern PA, near the Ohio border. I have WAAS on my garmin Etrex Legend, and 'use' it to increase accuracy.

 

I rarely, VERY rarely ever see my unit tell me that accuracey is better than 18 feet. 40 some odd feet is not uncommon either.

 

A month ago I was in Maryland visiting relatives and did a few caches. My GPS usually read 8 feet of accuracy. Eight feet! Wow.

 

Last week on the 14th around noon I had a very hard time getting a signal, and teh accuracy (claimed by my unit) was pushing 90 feet! This was the only time have had it sooo bad. I too was wondering about satellites or solar flares or whatever.

 

I was out on the 19th in more heavily forested woods and had an exceptionally good signal (about 1 mile from the area with a bad signal 5 days before).

 

It's a commie plot i tell ya.

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[You typed some stuff here.]

 

... All of these may be negligible factors as far as we are concerned, however, they all contribute and I am sure there are other factors I would never imagine. ...

 

[and some other stuff here]

So why the big argument? :P

 

You saw in my original post the word 'slightly', right? No one has claimed that there has been any huge changes to the earth's size or shape.

 

:P

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[You typed some stuff here.] 

 

... All of these may be negligible factors as far as we are concerned, however, they all contribute and I am sure there are other factors I would never imagine. ...

 

[and some other stuff here]

So why the big argument? B)

 

You saw in my original post the word 'slightly', right? No one has claimed that there has been any huge changes to the earth's size or shape.

 

B)

You asked.

 

I answered.

 

I wasn't arguing. I responded to your question.

 

Scroll up and read your own question if you don't believe me.

 

Edit: Also, you just said "shape" where before you said "size". Two different things. /Edit

 

I don't know why you are being so defensive but if its gonna bug ya, lets just forget it.

 

Happy Caching!

 

:P

 

And stop making those blinky eyes at me. You're weirdin' me out.

 

:PB)B)

Edited by tabulator32
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Don't know IF this has been addressed before . . . but, is it just the Carolina (USA)area OR is everyone having the difficulty of readings often-to-always being up to 25 feet off target.

 

It is getting really hard to find those micros-in-the-woods with a poor signal, tree cover and no hints even though I simply love these things and wish there were more of them.

i'v been haveing that problem here on the coast of or-wa

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So why the big argument?  :lol:

 

You saw in my original post the word 'slightly', right?  No one has claimed that there has been any huge changes to the earth's size or shape.

 

:D

...Edit: Also, you just said "shape" where before you said "size". Two different things. /Edit

Clearly, I included 'size' in my last post. :lol:

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Ok a bit more fuel to the fire.....

 

Actually the Earth's mass does increase slightly over time. I read somewhere that the dirt, ash, ice and other muck we scoop up everday in the form of meteors, meteorites, etc accounts for several thousand tons of new material each year spread across the planet....... :lol:

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As for the OP...if my GPS were consistently getting me within 25', I'd worship it. My readings this weekend were wildly off. Driving down the road, I kept losing signal, and when I did have signal, the topo map showed me driving hundreds of feet parallel to the road.

 

Do GPS units fail like that? I mean, by becoming a little off and a little hard of hearing? Or is it one of those "it's either working well or it's totally not working at all" deals?

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As for the OP...if my GPS were consistently getting me within 25', I'd worship it. My readings this weekend were wildly off. Driving down the road, I kept losing signal, and when I did have signal, the topo map showed me driving hundreds of feet parallel to the road.

 

Do GPS units fail like that? I mean, by becoming a little off and a little hard of hearing? Or is it one of those "it's either working well or it's totally not working at all" deals?

My coordinates this past weekend were good.

 

I don't know anything about the failure modes of GPS receivers, but I think lack of accuracy generally comes from not having a strong signal from enough sattellites--not from failure of the GPSr. The usual culprit at this time of year (in my experience) is foliage--especially pines.

 

Remember--if you are used to WAAS accuracy when in the open, then you can expect a significant loss of accuracy in the woods. The WAAS sattelites are in geosynchronous orbit over the equator; they do not pass overhead like the GPS constellation birds. If you do not have clear line-of-sight to the celestial equator, then you cannot expect WAAS accuracy.

 

When reception is poor, I generally find the best spot I can and stand still with the unit held up over my head (so as not to block the signals from one direction with my girthsome corpus). The instructions for my GPSr say it works best when held vertically--other units work better when held horizontally.

 

I wait until the bearing and direction have settled down (as long as two minutes), and then move to a closer position and try again. I ignore the jumpiness of the readings while I am moving.

 

Sometimes it helps to approach the coordinates from several different directions.

 

If reception is poor, then within twenty feet, it is time to put the gadget away and use your eyes.

Edited by reveritt
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This weekend, my husband practiced with the GPSr for the first time. I have always put in the coords, and used the thing. I can't tell you how many times he has found the cache while I stand waiting for the coords to settle.

 

Well, while he stood there, staring at the screen, I found all the caches we searched for.

 

Hmm..."You are the search engine". Dang, Jeremy is right..! :lol:

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It's not an urban legend. This is one of many sources of information.

 

However, the difference something like 3 billionth of a second per day - not enough to make micros any harder to find. :D

Right, so those of us who think there just isn't enough time in the day need only wait 333,333,333 days (913,242+ years) to get an extra second. See you then! :lol:

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Ok a bit more fuel to the fire.....

 

Actually the Earth's mass does increase slightly over time. I read somewhere that the dirt, ash, ice and other muck we scoop up everday in the form of meteors, meteorites, etc accounts for several thousand tons of new material each year spread across the planet....... :lol:

True. Not arguing that.

 

The statement that gave me problems was the one that said the Earth shrank in size when there was an Earthquake.

 

:D

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So why the big argument?  :D

 

You saw in my original post the word 'slightly', right?  No one has claimed that there has been any huge changes to the earth's size or shape.

 

:lol:

...Edit: Also, you just said "shape" where before you said "size". Two different things. /Edit

Clearly, I included 'size' in my last post. :lol:

Ok. Ok.

 

Everyone?

 

Just so everyone understands, for SBELL's sake, size DOES matter.

 

Alrighty?

 

Thanks!

 

:D

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Pardon me for my OP, it seems that my getting very used to 8-16 foot accuracy means I am a spoiled cacher . . . it is rare for me to see 25 feet accuracy. very rare.

 

Of course, under dense tree cover on a cloudy day, I may see the 25 feet situation and suffer greatly hunting micros 10 feet off the ground, an aw shucks moment.

 

This Saturday, in Charleston SC, it was raining heavily and obviously very cloudy and I was caching with a 9-12 foot accuracy . . . confirmed when I found the cache.

 

I have heard that reception can vary based upon the satellite positions, which ones you are reading, signal skip/bounce and other factors . . . all this being said, I like the 9 feet, it works for me.

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The changing of the seasons has my accuracy from the winter time average of 20' to the summer average of 50'. It's the cover around here. Although while out one day in a wide open area we obviously had sun spots or something. I was showing 5' accuracy and right on top of the cache (yes an urban micro at a light pole) all the sudden I went from being 10' from the cache to 300' from it. It zeroed out and then jumped to a couple of hundred feet again. It was a craz day of caching to say the least. We ended up sticking with micros instead of going up in the woods and running in circles.

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I know that the recent sunspots were predicted to have an adverse effect on the GPS system (I read that somewhere).

 

For the past week or two, I've seen my Magellan EPE go from 6-8 feet to as much as 90 feet. This past weekend, I logged six consecutive DNFs - some of them on AMMO CANS - just because they were all hidden in heavy cover areas where 30 feet off meant a whole lotta brambles to crawl throguh. And I declined to do so.

 

Okay, I may give up easily. But when I have six to eight satellites giving high bar signals and WAAS working, and STILL get an EPE of 40 feet...well, something is screwy.

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