Simple GPS question
 

Plain English answers will be required for this one.

I stealth camp and for safety reasons I'd like to be able to tell someone exactly where I am, long and lat wise. Is a simple and inexpensive GPS enough for that? Do rescuers use GPS's and could they find me from that information?

I will still be using charts for touring. This is just a once a day safety check in.

Even a poor GPS unit will probably report your position to within 100-200 m of your actual location. That should be good enough for rescuers.

I got a Garmin GPS 60 for about $150 and it has an accuracy of about +/- 20 feet.

So the plain English answer to your question is: "Yes"

I got a basic Garmin GPS on Ebay for $80.
For what you've described that sounds pretty good.
I'm not sure how well the average 911 center can
decipher a lat/long, though, maybe that's worth asking about.
Cheers,
Ed

Accuracy at its very best can be as good as 20 ft, but that's rare.
Expect that on top of a mountain with clear horizon all the way around you.
In a forest, with hills and stuff around you, 200 ft is good!

Another question is how are you going to relay that position to someone who can help. Does your cellular phone get coverage everywhere you've been?

The problem with GPS and maps is that they sometimes use different cartographic system. If you have to tell your position to someone, longitude and latitude are somewhat universal but require a bit more work to locate on a map. I am sure fireworkers, ambulance drivers and police officers have a basic knowledge of cartography and should be able to find you easily.

For the complicated answer: in Canada we usually use a Modified Mercator Transverse projection with a distinct grid system but on the edge you will also see long. and lat. references... these lines won't be straight on the map since the map is a projection of a round surface, the Earth, on a flat one. This is why it requires a bit more work to find lat and long on a map but most rescue team are well trained and might not even require studying the map... especially if they, themselves, use GPS.

Yes. A simple GPS will be fine for that, and there are several that can be found for less than $100.


This, I'm not sure about. I would hope that any kind of serious wilderness rescue team would easily be able to locate you with that info, but I really have no idea. If you're camped "somewhere off of I-80" and you call for help, I'm not sure if (for example) the highway patrol is set up to take raw coordinates versus a mile number or something.

Ramble: there are many GPS units out there and you can get all kinds of cool features (auto-routing, color, topo maps, etc), but basic GPSes for cheap which run on standard batteries include the Garmin eTrex "yellow", Garmin Geko 201, and the Garmin Foretrex 101. Going up a bit in cost, the eTrex Legend has a nicer (grayscale) display and can be found pretty cheaply now, and the eTrex LegendC sports auto-routing, a color display, a nicer user interface, and much longer battery life in basically the same package. For outdoorsy applications, I'm a fan of devices powered by AA cells for interchangeability and battery capacity reasons. Folks have been known to run their GPS receivers off of rechargeable AAs, but to carry a pack of lithium AAs (such as the energizer L91) as backup because they feature a long shelf life and good cold-weather performance.

-JAB

Another small note: when you first turn on a GPS unit, it can take anywhere from a few seconds to several minutes to get a location fix. If the unit has been off for more that a few minutes, or if it's been moved more than a few hundred miles while off, it will take longer. In my experience, it also takes longer to get that initial fix when the GPS is in motion, and of course when the sky is obstructed. Once the unit has "warmed up", so to speak, movement and obstructions pose less of a problem.

Calmly noting your coordinates after you've stopped sounds like a good idea. Also, as Magictofu pointed out, it wouldn't hurt to find out the preferred coordinate system of the rescue folks in your area.

-JAB

Simple in English answer: Yes it will work fine! The rescue dept's will also!

I love my GPS but discovered an error in the software. The Mapsource program had my train station 3 miles away from the actual location! Needless to say, I was pissed and now will use my Microsoft Streets and Trips to verify actual train stations or special locations.

If I were in the market for a new one, I would go for Megellon and spend for the color version. That sofware has to be better than Garmins.

Long and lat numbers are easy but the rescuers will have to be using the same system. As you can imagine, there are dozens of ways to get long and lat numbers and someone posted "Modified Mercator Transverse" which is one of many ways to determine longititude and lattitude.

I would feel safer just carrying a cell phone! After all, how are you going to be able to give them your long and lat figures without the phone??

Wouldn't WGS84 be the standard for all GPS units? At least all sold in the US?
At any rate, the differences between different systems are smaller than the normal inaccuracy of the GPS positioning itself.
You can give them the co-ords and expect them to find you unless you're hidden in some way.

If you just tell the emergency rescue center "I'm at N XX degs, YY.YYY minutes, E AA degs, BB.BBB minutes, and the datum is WGS-84", there is no way in hell that can be misinterpreted.

With a GPS, a flashlight, and general idea where your at, they will find you easy. And even the cheapest GPS units are usually 95 percent accurate within 20 feet and 60 percent accurate within 10 feet. But like someone said, if your cell phone don't work, you'll have no way of contacting emergency personnel. But don't sweat it, I stealthed all but one night on my 28 day tour and the biggest thing to distrub me was mosquitoes. You're be fine, just use common sense.

Cheers,
http://biketour.ne1.net

WGS84 is the standard for GPS in the US. The gov't used to add apprx. 150 meters of error to each measurement, called "selective availability". They have since taken out this intentional error (originally used so the enemy couldn't use our own system to hit us with exploding things) so recreational grade units, the only ones that are reasonably priced, get an accuracy of around 10 meters with a 95% confidence interval. That means that 95 times out of a hundred, the recorded position will be within 10 meters of the actual position. Tree trunks, buildings, high hills (and your body) can block satellite signals and reduce accuracy. Basically, anything that obscures your view of the horizon will reduce the accuracy. Beware of local interference, known as multi-path error. Chain link fences, metal watches, metal parts in a tent, bicycle frames and spokes, can cause the satellite signal to bounce around and reduce accuracy. GPS antennae that mount on the top of cars are shielded on the bottom to prevent this.
Lat/long are geographic coordinates, not projected, so they are universal. All phase II cell phones (all new models) come standard with built-in GPS which transmit lat/long automatically to many emergency services dispatchers. Any emergency service worth being rescued by will be able to work with lat/long coordinates.

That may work when talking to an emergency resuce center. What about when you dial your local 911 service?

Which 911 center will you get when using a cell phone. One center along interstate 80 is notorius for transfering 911 calls.

There is aome kind of gps that snow skiers use in case of avalanche that sends out a signal, I would imagine it would serve your need. Most outdoor recreation stores should have something like that. Some cell phones have GPS positioning on them for assistance too.