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Block IIF Satellites launching next month, huge accuracy increase...


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Okay, below is the information about the new IIF satellites that will soon launch which will provide us with much improved accuracy... do you think this will make the sport of geocaching to easy and eliminate a good portion of the hunt? I personally enjoy getting in the vicinity of a cache then hunting for it, rather than being within 2 feet and grabbing it right away... With this new system overhead tree's/brush wont affect signal... I hadn't seen much talk about this so i figured id start a topic. :huh:

 

The global positioning system works fine if you’re trying to persuade your phone to point you to the nearest bar or untangle a freeway interchange. But it’s not exactly accurate — GPS can be off by 15 feet or more, and the signal degrades when confronted with tall buildings and trees. It even gets screwed up by the slightest electromagnetic interference, like stray radio waves or storms in the ionosphere.

 

Hopefully this will soon be a distant memory. In May the Air Force will begin launching the so-called IIF generation of GPS satellites, which will eventually replace half the existing armada. The new birds each transmit three civilian GPS signals — we’ve typically been making do with just one for years — including a military-strength transmission that should enable autopilots to land with zero visibility. A three-signal world will mean always-on GPS that’s accurate to within 3 feet, even indoors and in concrete urban canyons. Forget finding the bar; you’ll be able to geolocate your stool.

 

source: http://www.wired.com/magazine/2010/04/st_gpsreboot/

Edited by FitzgeraldFamily
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All cache owners should be prepared to go out and obtain new coordinates?

 

I never get this "spot on coordinates makes geocaching too easy" thing. If anyone wants some extra challenge, I can write a simple GPX processor to add a random 10 ft jitter to all the waypoints in your GPX or LOC.

 

The Wired article is a little light on technical details. Not that I can understand too much technical details. I'd like to know how it can solve multipath - just by broadcasting a stronger signal? Will GPSr need to be updated with hardware or firmware? About the only thing I can predict is that this thread will get shipped off to the GPS and Technology forum as soon as a mod notices :huh:

Edited by Chrysalides
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You understand that receiving all three frequencies will require new receivers, right?

 

The multiple frequencies make real-time ionospheric depth corrections possible, so the major component of the WAAS corrections can now be done by your unit. Also, the clocks on the newer satellites are better. But I don't believe they do their own ephemeris corrections.

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You understand that receiving all three frequencies will require new receivers, right?

(comes back after reading a bunch of pages)

 

Do civilian handheld units today receive both L1 and L2, or only L2? Looks like the IIF will broadcast an additional L5 signal that should have much less interference.

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Do civilian handheld units today receive both L1 and L2, or only L2? Looks like the IIF will broadcast an additional L5 signal that should have much less interference.

Civilian survey-grade instruments can receive and use both L1 and L2 bands today. I believe that consumer-grade instruments only receive L1.

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Civilian survey-grade instruments can receive and use both L1 and L2 bands today. I believe that consumer-grade instruments only receive L1.

Thanks for the information. Other than the more accurate clock signals, I guess there's no immediate advantages for geocaching.

nope.

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The L1 frequency that your handheld GPSR uses is 1575.42Mhz. In my home workshop I use specialized fixed position timing L1 GPS receivers to access the atomic clocks on the GPS satellites to get frequency accuracy to parts in 10 to the minus 12 (parts per trillion) to synchronize my atomic clocks (doesn't everyone have an atomic frequency standard in their house? :rolleyes: )

 

One limitation on getting greater accuracy is the processor (CPU) speed in your GPS. Even now accuracy isn't that bad for geocaching if done properly and with care. My gut feeling is that geocachers won't see any significent difference between the old and new series of satellites. Paying attention to proper proceedure when placing a cache will have a far greater effect on accuracy. Newer GPSr will marginally improve accuracy over time as well.

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You understand that receiving all three frequencies will require new receivers, right?
(comes back after reading a bunch of pages)

Do civilian handheld units today receive both L1 and L2, or only L2? Looks like the IIF will broadcast an additional L5 signal that should have much less interference.

While there may be some dual-receive L1/L2 receivers on the market, as of last September there were only seven (7) L2 satellites in orbit. L2 does have a stronger signal but it's really only dependable when used in conjunction with L1. L5 will have a much stronger signal, but because it's on a different frequency, it'll require an L5 capable receiver. Keeping up with the Jonses is going to hit you hard in the pocketbook.

 

As far as multipath goes, there's really nothing that can compensate for true multipath. For example, in a high-rise environment like NYC, signals bounce around and you don't have much overhead. Those bounced signals travel further and that causes timing errors. Multipath is generally everywhere. Because signals degrade over time from moving through the atmosphere (attenuation) and because not all of the energy is reflected, a multipath signal is weaker than an unobstructed signal. But, because of the capture effect (strongest signal wins), the stronger signal from a "clear sky" always wins. However, under canopy or other obstructions, the overhead signal can be attenuated to the point where the multipath signal is actually stronger. Stronger signal wins and that gives us timing errors. GPS is all about timing. If the timing is off, the location is off. There are other considerations like signal-to-noise but generally it's all about the timing.

 

Bottom line is, as others have pointed out, we won't see any improvement in the game for a few years. And, when it does improve, expect to pay for it.

Edited by alwarren56
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The accuracy will always be off, that makes the game fun :rolleyes: (not) Remember though, if the person marking the coords has a 30 ft acc and there coords are off by 30ft then the seeker will be off by at least 30ft or more depending on there acc. For example, one of my caches is 70ft from the coords for many. But my Oregon gives me good enough acc already :rolleyes:

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I am new to geocaching but i am not new with GPS.

One thing i dont understand is so many people claim the GPS cords are always a bit off. Like people say, "my gps is off up to 10' and 10' for yours so give yourself 20' for searching..." that makes NO SENCE? how can a GPS be that bad? Maybe if you got it in a 5" thick rubber box with metal protection?

 

With clearskies a very cheap 5year old GPS will get you within 3'

With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

 

My 8900 gets GPS in a 3story building, under bridges, even in some sewer tunnels... THEN it bounces around 5'-25' but for the most part i am always DEAD on for all my cache. I walk till i see the cords matchup and with me standing still i can either SEE the cache up high or touch it....

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With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

What fairy tale are you living in?

 

Check your GPS manual. Even it only claims 10 meters without WAAS and 3 meters with WAAS.

 

I'm pleased when my GPS brings me within 10 feet of the cache.

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With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

What fairy tale are you living in?

 

Check your GPS manual. Even it only claims 10 meters without WAAS and 3 meters with WAAS.

 

I'm pleased when my GPS brings me within 10 feet of the cache.

 

Apparently the planets, moon and stars were aligned correctly once with a perfect satellite constellation because just once my 76csx went to zero and I looked down and there was the cache. Of course the next minute it said the cache was 8 feet that way.

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I am new to geocaching but i am not new with GPS.

One thing i dont understand is so many people claim the GPS cords are always a bit off. Like people say, "my gps is off up to 10' and 10' for yours so give yourself 20' for searching..." that makes NO SENCE? how can a GPS be that bad? Maybe if you got it in a 5" thick rubber box with metal protection?

It only makes *senSe* when you understand RF propagation.

With clearskies a very cheap 5year old GPS will get you within 3'

With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

Sorry, but you can't fight the laws of physics. Even in a clear sky, there are other factors that can and do affect accuracy. One in particular, the ionosphere, can have a huge impact even with crystal clear skys.

My 8900 gets GPS in a 3story building, under bridges, even in some sewer tunnels... THEN it bounces around 5'-25' but for the most part i am always DEAD on for all my cache. I walk till i see the cords matchup and with me standing still i can either SEE the cache up high or touch it....

My five year old non-HS Explorist has been dead nuts on several times. But as someone has already pointed out, that is nothing more than coincidence and pure dumb luck. I'm not saying it's not possible, but every signal would have to be attenuated equally with little to no multipath and an extremely low noise floor for that to be even remotely possible. You may have an HS receiver. But, no HS receiver can compensate for multipath and unequal attenuation. Me thinks a quick study of the fundamentals of RF propagation might be in order here.

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I dont know what fairy tail im living, the one that i live in?

All i know is when it says 0-3' on my 8900 the cache is generally RIGHT THERE.

 

Now my 5 yr old nuvi is a bit worse.

When driving down the highway it will say i am on the access road, when its cloudy.

Clear skies it knows if i am on the access road or the main road. (no it cant tell due to speed, i tested this)

 

I have yet to see a cache be more than 3' from it posted cords... (on a clear day without cover)

but i only have 26 finds so....

 

Also all GPS do the 10m claim.... they always state they are worse than what they are...

 

edit:

Cache today, clear skies, not under heavy trees. Was off by about 6'....

Cords had me on a walkway, the cache was in a tree off the walkway..

 

edit:

3am, -6gmt, clear skies, windy (not that it matters..) and i am picking up 7 sats... accuracy of 2.23m according to my crappy phone :rolleyes: so 7' or so...

(also note i am standing RIGHT outside my door of a 2 story house... not going to walk outside to the street...)

 

I stand corrected....

 

I just been getting lucky i guess... And the app i use for GPS does a avg of the cords. So instead of bouncing me all over the place like i know some people see, mine shows me the avg of my loction, so i am standing still...

Edited by viper1986
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Anybody who feels nostalgic for the old, lower accuracy system can use an old, less accurate unit.

 

Heres another point that SOME tend to forget.

 

Geocaching requires the use of at LEAST 2 GPSr's. Why do you say two?

 

1. The Cache Owner needs a GPSr to get the correct coordinates to create a geocache. His GPSr will have a margin of error. Depending on what she/he used. It could be around 20'. Maybe less if they have a better GPSr. Worse if they have an older or el cheapo.

 

2. The geocacher's GPSr that searching for the cache. If his is off by 20' and the CO's is off by 20'. You could end up with an error of as much as 40' in some cases.

 

Even with an accuracy of 10' sometimes it can still be VERY difficult to find some caches. It could point to a 100 year old oak tree. This oak tree could have a 1000 holes in it's trunk.

 

What I will be looking for with the new satalites and new GPSr's that will support the new satalites is having a GPSr that will work better when you have a canopy of Trees over your head!

 

TGC

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With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

What fairy tale are you living in?

 

Check your GPS manual. Even it only claims 10 meters without WAAS and 3 meters with WAAS.

 

I'm pleased when my GPS brings me within 10 feet of the cache.

 

Apparently the planets, moon and stars were aligned correctly once with a perfect satellite constellation because just once my 76csx went to zero and I looked down and there was the cache. Of course the next minute it said the cache was 8 feet that way.

 

Try geocaching in Europe (without WAAS). I went out this morning for a nice walk and to look for a few caches in Montpellier (France). At the first one I looked for my GPS took me to a spot and told me I was 4' away from the published coordinates. I looked around a bit then checked my GPS again and it said I was 60' away. That was fairly typical for the other caches I found this morning as well. The narrow streets with some tall buildings and all of the caches being micros or nanos didn't make it any easier.

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Try geocaching in Europe (without WAAS). I went out this morning for a nice walk and to look for a few caches in Montpellier (France). At the first one I looked for my GPS took me to a spot and told me I was 4' away from the published coordinates. I looked around a bit then checked my GPS again and it said I was 60' away. That was fairly typical for the other caches I found this morning as well. The narrow streets with some tall buildings and all of the caches being micros or nanos didn't make it any easier.

the highlighted part is what killed your accuracy, not the lack of WAAS.

Edited by dfx
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I have to add this.....

Today at 19:00 -6gmt i turned on my GPS outside on clearweather in a field...

10 satilittes hitting my GPS... with accuracy of 1.25m...

I guess it also depends on where you live. Not all places across the world have that many sats that hit their GPS device...

So i guess it is just where i live that causes me to never have one of those cache that is 10' from its posted cords...

Edited by viper1986
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I am new to geocaching but i am not new with GPS.

One thing i dont understand is so many people claim the GPS cords are always a bit off. Like people say, "my gps is off up to 10' and 10' for yours so give yourself 20' for searching..." that makes NO SENCE? how can a GPS be that bad? Maybe if you got it in a 5" thick rubber box with metal protection?

 

With clearskies a very cheap 5year old GPS will get you within 3'

With a NEW GPS (iphone/blackberry/any car based GPS) you should get within 1' of the location with clear skies...

 

so sorry, but you are wrong.

 

for a while I was geocaching with a 7 year old GPS, and man did it SUCK!!!

 

It was ALWAYS 80- 100 feet off.

 

I easily found one cache once that was 80 feet off because I was so used to walking in large circles. I got email from other cachers asking me how I found the thing.

 

I cached sometimes with someone else who had a new GPS and he was always right on. He would be looking 80-100 feet from where I was looking so it had nothing to do with the satelites or terrain.

 

Now I've got a new model that is fantastic!! It is as accurate as the GPS that placed it. I can tell if someone placed the cache with a new GPS because I will be right on it.

 

I recently cached with someone who used an I-phone with a GPS app.

The accuracy was so bad that when she tried to place caches everyone complained about them being 100 feet off.

I went and got new coords for her with my new GPS.

 

Let me tell you, all GPSr's are not created equal!!!

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I have to add this.....

Today at 19:00 -6gmt i turned on my GPS outside on clearweather in a field...

10 satilittes hitting my GPS... with accuracy of 1.25m...

That's estimated accuracy. Your unit's being generous.

Anyways, error sources and general distances:

Sources of User Equivalent Range Errors (UERE)

Source Effect (m)

Signal arrival C/A ±3

Signal arrival P(Y) ±0.3

Ionospheric effects ±5

Ephemeris errors ±2.5

Satellite clock errors ±2

Multipath distortion ±1

Tropospheric effects ±0.5

C/A ±6.7

P(Y) ±6.0

There is also a numerical error with an estimated value, "Onum", of about 1 meter.

 

If you live in an area without much in the way of terrain you may enjoy more consistent signal, but anything claiming better than 2m is certainly lying to you.

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