GPS Signal

[+Skytraveler]

Can anyone tell me how often they cannot get a strong enough signal to use their GPS system? I have found that about 25% of the time I cannot use my GPS because of signal strength. I just wanted to know if this is common, or if it's just my GPS. Thanks.

 

Dark Skies!

[+Prime Suspect]

Basically, never. I'm, of course, excluding those occasions where you wouldn't normally expect to get a signal (in a tunnel, under some structure, etc.). But generally if I've got sky overhead, I can eventually get a lock. The accuracy may be in triple digits, but it's calculated a solution. Whether it's good enough for caching is another matter. Sometimes you have to move to an open area to get a good lock, then figure out where the cache should be based on the offset from your current position. That's part of the game.

 

[+Ranz]

What kind of GPS is it?

This would tell me if it has a quadrifier or patch antenna.

 

Where are you trying to use it when you are not getting signal?

GPS's are line-of-sight devices, meaning they work best if their view of the sky is not obstructed. Heavy tree cover, indoor use, tall buildings or hills all have an effect on performance. The level of effect they have is also related to the antenna type.

 

I can imagine that level of performance under certain circumstances but generally speaking, if you are out in the open you should see at least five or six satellites. They may not max out the bars on signal strength but that is not a important as the number you acquire.

 

Ranz

 

[Kerry.]

Sounds like an issue with your GPS and/or the environment you are using it.

 

On the system side there shouldn't be any issues with signal strength at all.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

Sounds like an issue with your GPS and/or the environment you are using it.

 

On the system side there shouldn't be any issues with signal strength at all.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+Pat in Louisiana]

I sometimes loose signal in heavy cover and on cloudy days. The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

 

Pat in Louisiana

I never get lost. I simply investigate alternate destinations.

[+Pat in Louisiana]

I sometimes loose signal in heavy cover and on cloudy days. The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

 

Pat in Louisiana

I never get lost. I simply investigate alternate destinations.

[Jeremy]

I believe it may have to do with the large number of geocaches in your area. If there are a lot of geocachers you may not be able to get a signal since they're all using up the GPS bandwidth.

 

(The above was a joke. California has 4 times as many caches as any other state)

 

More likely you are in a deep crevasse (like between large buildings, or in a valley), or under heavy tree cover. Since satellites need to be basically "line of sight" within reason, there are a great many times when it won't work well. Improving your signal would involve using an external antenna (though some internal antennas like the Meridian Gold would beat an eTrex), or getting a good lock in a clearing before heading deeper under tree cover. If you have a non-Magellan or Garmin unit, you also have to rely on the manufacturer and their track record.

 

When hiking, I use a cell phone attachment on my backpack (which attaches to the strap), so my GPS unit is positioned in such a way that it maintains a signal. Putting it in your pocket when hiking will break the lock, and it is much harder to acquire a lock than to maintain one.

 

Jeremy Irish

Groundspeak - The Language of Location

[Jeremy]

quote:

---

Originally posted by Pat in Louisiana:

The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

---

 

Your GPS makes some assumptions when you're travelling in a vehicle. It will look as though it maintains a lock when it is really just projecting your movement. If you leave the tunnel fast enough it will pick the lock back up and continue on happily. It happens to me all the time when I head through the tunnel on Mercer Island on my way to Seattle, though the second tunnel is just long enough that it will beep at me a couple hundred yards before the tunnel exit.

 

Jeremy

 

Jeremy Irish

Groundspeak - The Language of Location

[Jeremy]

quote:

---

Originally posted by Pat in Louisiana:

The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

---

 

Your GPS makes some assumptions when you're travelling in a vehicle. It will look as though it maintains a lock when it is really just projecting your movement. If you leave the tunnel fast enough it will pick the lock back up and continue on happily. It happens to me all the time when I head through the tunnel on Mercer Island on my way to Seattle, though the second tunnel is just long enough that it will beep at me a couple hundred yards before the tunnel exit.

 

Jeremy

 

Jeremy Irish

Groundspeak - The Language of Location

[+Alan2]

Originally posted by Pat in Louisiana:

...The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

 

QUOTE]

Gee, I hope the tunnel isn't leaking.

 

Alan

[+Alan2]

Originally posted by Pat in Louisiana:

...The strange thing is that the other day I went through the Mobile Bay Tunnel in Alabama twice and never lost signal

 

QUOTE]

Gee, I hope the tunnel isn't leaking.

 

Alan

[+Alan2]

quote:

---

Originally posted by Jeremy Irish:

 

Your GPS makes some assumptions when you're travelling in a vehicle. It will look as though it maintains a lock when it is really just projecting your movement. If you leave the tunnel fast enough it will pick the lock back up and continue on happily. It happens to me all the time when I head through the tunnel on Mercer Island on my way to Seattle, though the second tunnel is just long enough that it will beep at me a couple hundred yards before the tunnel exit.

 

Jeremy

 

Jeremy Irish

Groundspeak - The Language of Location

---

 

My Vista will store it's minus -4o feet altimeter reading on the tracking that it sees while I'm in a tunnel onto the last and first actual GPS positions before and after the tunnel. Obviously there's no satellites position recorded while in the tunnel. It took me a while to figure out that was the reason the toll takers appear to be working underwater. The Vista program is set up that way.

 

I wonder if skiers get similar tracks recordings when they lose lock going down a mounntain under tree cover. The altitudes on the tracks sometime might not be where they should be. Any skiers out there with Vistas.?

 

Alan

[+EraSeek]

quote:

---

Originally posted by Pat in Louisiana:

I sometimes loose signal in heavy cover and on cloudy days. .

---

 

Cloudy days will have no effect on your signal. Neither rain nor snow nor dark of night. Tree cover, yes.

 

[CountryLover]

Not sure 'cos I think the satellites are supposed to be geostationary or something ? . . .

 

What I've noticed is I get different signal levels from the satellites at different times and days from exactly the same spot. Only difference is cloud cover which can be extensive here which I notice DOES make a noticable difference.

[Kerry.]

quote:

---

Originally posted by CountryLover:

Not sure 'cos I think the satellites are supposed to be geostationary or something ? . . .

 

What I've noticed is I get different signal levels from the satellites at different times and days from exactly the same spot. Only difference is cloud cover which can be extensive here which I notice DOES make a noticable difference.

---

 

NO affect from the cloud but all the satellites are in fact moving (about 4000m/second) and not geo-stationary, so at different times of the day one will generally be seeing combinations of different satellites, in different relative locations and signal strengths will certainly vary as individual satellites "rise and set".

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by CountryLover:

Not sure 'cos I think the satellites are supposed to be geostationary or something ? . . .

 

What I've noticed is I get different signal levels from the satellites at different times and days from exactly the same spot. Only difference is cloud cover which can be extensive here which I notice DOES make a noticable difference.

---

 

NO affect from the cloud but all the satellites are in fact moving (about 4000m/second) and not geo-stationary, so at different times of the day one will generally be seeing combinations of different satellites, in different relative locations and signal strengths will certainly vary as individual satellites "rise and set".

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+unclerojelio]

quote:

---

Originally posted by Jeremy Irish:

 

(The above was a joke. California has 4 times as many caches as any other state)

 

---

 

Yes, but have you noticed that state ( or in this case, district) with the most caches PER SQ MI? Turns out that you can't swing an expired feline without tripping over a cache in DC.

 

... Two roads diverged in a wood, and I--

I took the one less traveled by, ...

 

unclerojelio

[+unclerojelio]

quote:

---

Originally posted by Jeremy Irish:

 

(The above was a joke. California has 4 times as many caches as any other state)

 

---

 

Yes, but have you noticed that state ( or in this case, district) with the most caches PER SQ MI? Turns out that you can't swing an expired feline without tripping over a cache in DC.

 

... Two roads diverged in a wood, and I--

I took the one less traveled by, ...

 

unclerojelio

[mcb]

GPS satellites are NOT in a geosynchronous orbit. They are in an orbit at about half that altitude. Geosynchronous orbit is about 22,000 mile and GPS satellites are in an orbit at about 11,000 miles that make their orbit about once every 12 hours. The two WAAS satellites (which are actually telecommunication satellite being multi-tasked) are in Geosynchronous orbit. Hence the reason you always see the same WAAS bird 35 here in the easter half of the US and I think the west coast WAAS satellite is 42? And yet with the rest of the GPS satellites you almost always see a different set of satellites above the horizon. On top of being on a twelve hour orbit the GPS satellites are also distributed in several different orbital planes that are tilted at an angle (I beleive 56 degree) to the rotational axis of the earth. This make for a constantly changing number and geometery of satellites your GPS unit will see above the horizon.

 

So there is a very slim change that given the enviroment around you may not be able to get a lock but this is very unlikely. With a fully populated constilation of satellite (24 satellite is specified for the GPS system) then you should have at least four satellite about the horizon anywhere on the planet something like 99.9... percent of the time. I don't rember the actual number but it was very close to one hundred percent of the time. Any right now I beleive the constilation is over populated with 26 or 27 satellites. The problem arises if you are not able to let the GPS receiver see enough of the satellite that are above the horizon. Your body, trees, canyon walls, building, etc all may block the signal. So if you are having trouble locking on then I would try to get a better veiw of the sky. You should rarely if ever not have enough satellites to get a lock. Weather should never be a factor except making tree wet and better signal blockers. Rain, snow, heavy clouds, fog should have very little if any effect on the signal strength recieved.

 

mcb

 

GPS-Yote

[Geonavigator]

I use a GA 27C Low Profile GPS Antenna on a Garmin 76 to improve signal strength in dense vegetation. The antenna amplifies the signal significantly - stronger signals that are seldom lost. I pin the antenna to the rear of my coat collar facing the sky. The antenna and wire doesn't get tangled in the brush and the GPS can be placed inside a pocket. The antenna does decrease battery life. Possibly an external antenna could help improve signal strength in your area.

[+Skytraveler]

Hi, this is the original poster. Based on everyone's replies I must furnish some information. I am using a Megellan Navman GPS unit that hooks onto the back of my Palm M515. It looks like a sled that the Palm unit rides on. The software I am using is Cetus GPS. This software will let you see the satellites overhead and tell you the signal strength from each. When I check the signal strength I am getting 3 bars from about 7 to 8 statellites (usually). The problem is it won't give me a position until atleast 2 have a signal over 4 bars. If I get 3 statellites over 4 bars then I get altitude as well. Maybe this GPS unit isn't all it's cracked up to be. What do you think?

 

Dark Skies!

[+GoldKey]

quote:

---

Originally posted by Skytraveler:

Hi, this is the original poster. Based on everyone's replies I must furnish some information. I am using a Megellan Navman GPS unit that hooks onto the back of my Palm M515. It looks like a sled that the Palm unit rides on. The software I am using is Cetus GPS. This software will let you see the satellites overhead and tell you the signal strength from each. When I check the signal strength I am getting 3 bars from about 7 to 8 statellites (usually). The problem is it won't give me a position until atleast 2 have a signal over 4 bars. If I get 3 statellites over 4 bars then I get altitude as well. Maybe this GPS unit isn't all it's cracked up to be. What do you think?

 

Dark Skies!

---

 

My first GPS was the Navman for the Palm III. I got it thinking I could have an alternate use for my old palm after I got an Ipaq. I hated it. It took forever to acquire a signal and would not hold it very well. Plus it had built in nonreplaceable rechargable batteries that wore out pretty quickly. Would not have enough power to do any long caches. Also, the model is not really suited for rugged use. I have dropped my Etrex a number of times without a problem. Had it been my palm it would have broken. On the plus side, it was really cheap (like $50) and had maps and a carmount/auto power adapter.

[+Dan_Edwards]

quote:

---

Originally posted by Skytraveler:

Hi, this is the original poster. Based on everyone's replies I must furnish some information. I am using a Magellan Navman GPS unit that hooks onto the back of my Palm M515. It looks like a sled that the Palm unit rides on. The software I am using is Cetus GPS. This software will let you see the satellites overhead and tell you the signal strength from each. When I check the signal strength I am getting 3 bars from about 7 to 8 satellites (usually). The problem is it won't give me a position until at least 2 have a signal over 4 bars. If I get 3 satellites over 4 bars then I get altitude as well. Maybe this GPS unit isn't all it's cracked up to be. What do you think?

 

Dark Skies!

---

 

I am using a Visor and Magellan GPS, and Cetus GPS.

 

For GPS you need 3 sats for a 2D lock, and 4 for a 3D lock. For a 3D lock you need the sats spaced over a little bit of the sky. A couple of times I have had 5 sats and only a 2D lock.

 

That said, I have noticed that what Cetus GPS reports for sats and locks is different sometimes then the built in software on the GPS. I have seen it say a 3D lock with two sats and the built in software will say 2 Sats and no lock. I was getting a lock in my basement because I was trying to duplicate low signal areas at the time.

 

Personally I have found my Magellan to be very good at maintaining a lock, and extremely accurate for a non-waas GPS.

 

On a side note, your note made me download the latest version of Cetus GPS. It now looks to be stable on my Visor Deluxe! Yea, I have never had a version of that program that was stable on my system before. I love the interface but never could have it run long enough to find a cache with. Can't wait to test it out this weekend. Of course I will also have the cords in two other GPS programs and on paper, just in case

[+Dan_Edwards]

quote:

---

Originally posted by Skytraveler:

Hi, this is the original poster. Based on everyone's replies I must furnish some information. I am using a Magellan Navman GPS unit that hooks onto the back of my Palm M515. It looks like a sled that the Palm unit rides on. The software I am using is Cetus GPS. This software will let you see the satellites overhead and tell you the signal strength from each. When I check the signal strength I am getting 3 bars from about 7 to 8 satellites (usually). The problem is it won't give me a position until at least 2 have a signal over 4 bars. If I get 3 satellites over 4 bars then I get altitude as well. Maybe this GPS unit isn't all it's cracked up to be. What do you think?

 

Dark Skies!

---

 

I am using a Visor and Magellan GPS, and Cetus GPS.

 

For GPS you need 3 sats for a 2D lock, and 4 for a 3D lock. For a 3D lock you need the sats spaced over a little bit of the sky. A couple of times I have had 5 sats and only a 2D lock.

 

That said, I have noticed that what Cetus GPS reports for sats and locks is different sometimes then the built in software on the GPS. I have seen it say a 3D lock with two sats and the built in software will say 2 Sats and no lock. I was getting a lock in my basement because I was trying to duplicate low signal areas at the time.

 

Personally I have found my Magellan to be very good at maintaining a lock, and extremely accurate for a non-waas GPS.

 

On a side note, your note made me download the latest version of Cetus GPS. It now looks to be stable on my Visor Deluxe! Yea, I have never had a version of that program that was stable on my system before. I love the interface but never could have it run long enough to find a cache with. Can't wait to test it out this weekend. Of course I will also have the cords in two other GPS programs and on paper, just in case