Like to go way out there? Trust your GPS? Read this... (1 Viewer)

[GeoRoss]

they can do it quite easily. There are two flavors of GPS, regular and differential GPS. Plain ole consumer GPS, where they "inject" errors (mathmetical algorythym variation)to purposely fuzz your position a bit. Also,notice you dont lock onto 12 simultaneous satellites that your GPS manufacturer says you can. The feds mandated a maximum to reduce the pinpoint.

'Selective Availability' has been turned off for several years now. There is no error being included in the radio signal as of this time. However the military has stated they will bring it back if necessary. I have heard several stories about why it was turned off, mostly that the included error was effecting the military's precision.

Eric, your experience near the White House is interesting. They must have some sort of jamming going on there.

Differential GPS doesnt have the algorythym injection, so it is as close to sayin 'YOU ARE HERE DIPSHIT1!!!!" Mainly a military toy, but it is gettin out to commercial channels.

Differential GPS (DGPS) is not a military toy. All it is GPS basestation with a location of known precision. This receiver must be within 150 miles or so of the rover and must be seeing the same sats, closer being better. The base station receives the same signal as the rover and calculates the error based on the sat determined location and the known location. The rovers positions can be later corrected or in real time, the basis of the near shore WAAS stations or by using some other radio transmitted correction.

There are web sites that you can go to and get the error correction data to correct your data if you are near enough a published GPS station.

This being said, if you think you need more that 5m accuracy in the consumer market, forget. 5m is about as good as it can get with out using some sort of DGPS.

Ross

 

[Mark W]

I routinely see my cheap ass Garmin *claim* that it is working at +- 15 feet accuracy...


Mark...

 

[e9999]

I suppose that the white house could jam your GPS but I can't see that well how the satellite would know where you are and generate errors just when you're near the White House and not elsewhere. After all, this thing is just measuring the distance from the satellite.

 

[e9999]

I routinely see my cheap ass Garmin *claim* that it is working at +- 15 feet accuracy...


Mark...

my little Magellan has claimed 9ft accuracy with WAAS on. Now whether that is true or not...

 

[rusty_tlc]

I suppose that the white house could jam your GPS but I can't see that well how the satellite would know where you are and generate errors just when you're near the White House and not elsewhere. After all, this thing is just measuring the distance from the satellite.

A re-broadcast antenna.
One way to improve your GPS reception inside a steel vehicle is to mount a re-broadcast antenna. This is how it works, an external antenna receives the GSP signals, another antenna inside the vehicle re-broadcast the signals.

The fuddle a GPSr near the white house or pentagon or wherever just set up a re-broadcast antenna that swamps the satellite signals.

 

[Zimm]

i guss thats good for protecting the WH from some cheap missle, but bad for the dud in a "jump to" location.

 

[lowenbrau]

I pulled the fuzzy batteries out of my GPS a few months ago and put some new ones in. Yup it still works. Its back at the bottom of the glovebox ( I think) where I'm sure to forget it if I get lost.

The only deserts I've crossed were on the I-15 and I've never driven across the ocean. Everywhere else seems to a have a river or mountain range and with the exception of some trips way up north I've always found the sun to rise more or less in the east and head west-ish all day. The best technology I've found yet for finding my way home is gravity. Those streams all become rivers eventially and sooner or later I'll find a town on one. Worst case I'll end up at an Ocean somewhere.

 

[rusty_tlc]

I pulled the fuzzy batteries out of my GPS a few months ago and put some new ones in. Yup it still works. Its back at the bottom of the glovebox ( I think) where I'm sure to forget it if I get lost.

The only deserts I've crossed were on the I-15 and I've never driven across the ocean. Everywhere else seems to a have a river or mountain range and with the exception of some trips way up north I've always found the sun to rise more or less in the east and head west-ish all day. The best technology I've found yet for finding my way home is gravity. Those streams all become rivers eventially and sooner or later I'll find a town on one. Worst case I'll end up at an Ocean somewhere.

A GPS is a good tool. One that has topo maps loaded is a very usefull tool. It can help prevent you from following the wrong creek and winding up in worse shape than when you started.

We do a fair amount of road trips and I find the POI (Points of interest) to be usefull, kind of nice to be able to pull up the distance to the next rest stop.

 

[Mark W]

I pulled the fuzzy batteries out of my GPS a few months ago and put some new ones in. Yup it still works. Its back at the bottom of the glovebox ( I think) where I'm sure to forget it if I get lost.

The only deserts I've crossed were on the I-15 and I've never driven across the ocean. Everywhere else seems to a have a river or mountain range and with the exception of some trips way up north I've always found the sun to rise more or less in the east and head west-ish all day. The best technology I've found yet for finding my way home is gravity. Those streams all become rivers eventially and sooner or later I'll find a town on one. Worst case I'll end up at an Ocean somewhere.

We were talking about this (follow the steams downstream) just the other day. We had a couple of teenagers out for an afternoon of goofing off make the mistake of doing this when they got turned around. One of them died from exposure a couple of days later as they hiked further away from everything.

You remember that nice long run of mud in the little valley when you were up here for ACT2001? The one where we quit at about midnight 'cause Gina had the busted center pin?
If you had been lost and decided to follow that creek downstream to eventually reach "civilization"... You would have wandered through nearly a hundred miles of non-"vehicle friendly" marsh to reach a river which would eventually (another 50+ miles) lead you to an impassable canyon with class 6+ rapids. A ways downstream from there you'd pass under a highway bridge. If you somehow managed to miss the bridge... wandering through the night in an exhaustion induced delerium maybe ... another 100 miles or so would bring you to the edge of the inlet. Maybe only 20 miles of quicksand like mudflats to the road system... IF you turned the right way. :whoops:

The "follow the river dowstream" advice works when you are in developed country, but only then. Well, maybe if you're in a boat with lots of fuel on hand...


BTW, does it look like we're gonna see ya up again next year???? I've got a great route scouted out... And a stretch up in the high country that NO ONE has ever run before just waiting for the right mix of guys to tackle it...

Mark...

 

[rusty_tlc]

...

The "follow the river dowstream" advice works when you are in developed country, but only then. ...

Mark...

Every year a couple of skiers/snowborders go out of bounds at Tahoe, specifically Mt Rose. Up there just going to the right of a tree instead of the left can take you down the wrong side of a ridge and miles from the resort. A very bad situation during winter conditions in the Sierra. So even in developed country following the "river" may not work.

 

[lowenbrau]

We were talking about this (follow the steams downstream) just the other day. We had a couple of teenagers out for an afternoon of goofing off make the mistake of doing this when they got turned around. One of them died from exposure a couple of days later as they hiked further away from everything.



Mark...

That's a sad story. Don't get me wrong, I get lost a lot. That is part of the fun of leaving the maps at home. I'm increasingly of the opinion that being prepaired means leaving most of the crap at home. No disrespect intended but those kids probably had all the gear they needed to live a good long time while lost. What they didn't have was the experience and training. That's unfortunate. The best money I ever spent on a course was a wilderness survival course where we spent five days in the bush in below freezing conditions without food or shelter. You learn to worry less about the fact that you are 'lost' and concentrate on living. It turns out that it can be quite enjoyable living once you get your head around the fact that you are not going to get your morning coffee.

Anyway, your point is well taken... The sun is not reliable in AK so why should the gravity be? I'll be sure to employ a guide next summer. You still taking payment in Cola products?

 

[Mark W]

That's a sad story. Don't get me wrong, I get lost a lot. That is part of the fun of leaving the maps at home. I'm increasingly of the opinion that being prepaired means leaving most of the crap at home. No disrespect intended but those kids probably had all the gear they needed to live a good long time while lost. What they didn't have was the experience and training. That's unfortunate.

Actually they had no gear at all. Sneakers, jeans and tshirts basically. Out for a summer afternoon of hiking and goofing off within a short hike of the car in a commonly used recreationalk area right on the edge of things. They clibed over a ridge got to playing around on a snow field and lost track of where they were at/where they came from. Common sense would have seemed to dictate climbing back up, but for some reason they remembered someone telling them to follow creeks dowmstream. The survivor was found by chance two days later by a helicopter which was trying to get around nsty weather to reach the are where they were expecting to be searching. Like you said. Sad. Just dumb kids basically who had no expectation of needing to be prepared at all.


QUOTE=lowenbrau]The best money I ever spent on a course was a wilderness survival course where we spent five days in the bush in below freezing conditions without food or shelter. You learn to worry less about the fact that you are 'lost' and concentrate on living. It turns out that it can be quite enjoyable living once you get your head around the fact that you are not going to get your morning coffee. [/QUOTE]


I absolutely agree with that! The right attitude is by far the most important thing to have along...


QUOTE=lowenbrau]Anyway, your point is well taken... The sun is not reliable in AK so why should the gravity be? I'll be sure to employ a guide next summer. You still taking payment in Cola products?[/QUOTE]


That sounds like at least a "probably maybe" answer to my question? Great. Bring a sixpack and I'll consider myself hired.

If we wind up with a small group of "serious" guys who pretty much know each other beforehand it'll be one heck of a run. If not it'll still be a heckof a lot of fun but maybe not as "Epic".


Mark...

 

[alvarorb]

And if you have the GPS connected to a laptop, you should be safer, I would think since those are probably shielded much better.

Eric,

I would not depend on Windows to get me back home. I'd rather use a GPS with it's own OS. Less cables, less clutter, less things to go wrong. Sure having the GPS attached to a laptop is awesome. There are many things you can do. Having a paper map of the area as backup is great.

I'm not familiar with the Magallean. When I used my e-trek Vista from Garmin, it went out on me a couple of times. However, the 276C has been rock solid.

Regards

Alvaro

 

[e9999]

dammit!
it happened again.
Was in the Sierra Madres near Cuyama on a ridge. There is a microwave relay station and it wiped out the whole GPS clean. Not only the track I had just laid, but all my points of interest including the little secret beaches in Baja and all....
Dang piece of cr@p!

 

[alvarorb]

dammit!
it happened again.
Was in the Sierra Madres near Cuyama on a ridge. There is a microwave relay station and it wiped out the whole GPS clean. Not only the track I had just laid, but all my points of interest including the little secret beaches in Baja and all....
Dang piece of cr@p!

Solution:

Get an external antenna and wrap your GPS in foil.
Maybe it will keep it safe

Regards

Alvaro

 

[thekirk]

What brand of GPS is this happening with? I've had my Garmins near some pretty extreme RF sources, in the military, and I've never had that happen. I'd be wondering if the shielding on yours isn't damaged, or something.

A well-designed GPS is going to be shielded against most stuff you'd commonly encounter--like the RF field around powerlines. Unless you were right up next to the dish, trying to heat some hot dogs, you shouldn't have seen any effect. The most that should happen is that your GPS unit may lose the satellite lock that it had, and you'd need to move out of the area in order to get a signal. If there is RF energy penetrating the case, and the shielding that should be in place, something is seriously wrong with your unit.

Hell, I parked next to a transmitting microwave dish with mine, one time (didn't know it was in use, they were shutting down operations, and of, course, pulled the safety signs and such, first...), and the damn thing melted some candybars I had on the HMMWV radio rack. My Garmin never skipped a beat, that I noticed.

 

[rusty_tlc]

dammit!
it happened again.
Was in the Sierra Madres near Cuyama on a ridge. There is a microwave relay station and it wiped out the whole GPS clean. Not only the track I had just laid, but all my points of interest including the little secret beaches in Baja and all....
Dang piece of cr@p!

You lost data that you didn't have backed up and you are blaming the electronics?
Rule one: save early and save often, as true today as it was when I learned Fortran oh so many years ago.
The first thing I do when I get home from a trip where I collected waypoints is download them to my PC.

As somebody else mentioned you may have a problem with the shielding on your unit. I use a Magellan Meridian and have driven straight through Antenna farms on a couple of occasions with no problems.

 

[e9999]

You lost data that you didn't have backed up and you are blaming the electronics?
Rule one: save early and save often, as true today as it was when I learned Fortran oh so many years ago.
The first thing I do when I get home from a trip where I collected waypoints is download them to my PC.

As somebody else mentioned you may have a problem with the shielding on your unit. I use a Magellan Meridian and have driven straight through Antenna farms on a couple of occasions with no problems.

thanks for the advice on backup. Particularly easy on this one since it doesn't have provisions for a PC connection...

 

[e9999]

I'm gonna call Magellan and see what they can tell me...

 

[thekirk]

e9999--There's got to be something wrong with your unit. I was talking about this with someone here at work, and they agreed with me. Lost signal, due to RF, yes, certainly. Lost data on the unit? No way, unless something is wrong with the unit, or with the unit's shielding.

As a possible explanation, check the unit's specifications. Somewhere it will say something about environmental conditions it's supposed to be able to operate in, and should say something like "compliant with MILSPEC something-something", the way my Garmins do. MILSPEC is Military Specification, and tells you what the system is rated to. It's often used as an industry standard, as well. If your Magellan unit wasn't built to a MILSPEC standard, that might explain why it's zeroing itself out on you, around RF energy sources...