doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Global Positioning System

I am thinking about getting a GPS unit to bring with me while I'm hunting,fishing or just out in remote areas. Does anyone on the forum have any specific recommendations on what to buy in this area?
Jim

Garmin Etrex.....cheap simple easy to use......99.00 Ebay

Do you want one that shows the roadways, etc for your car, too ?
Some of these can be carried along on foot, too.

I have had mine for 10+ years. It is an Eagle brand, lat4er bought out by Lowrance. Any of the Garman,or Lowrance models will work fine. Some have downloadable software that includes maps of exatly where you are. When I finally bust down and get a new one, I'll choose a model that can download maps. I mainly use my GPS to mark the location of my truck, or camp and then use dead reckoning to hunt. That way I can concentrate ion my hunting and not on navigation. If this is what you're planing to use it for, then I'd suggest the small Garman models that you can pick up for $99. They're very compact and accurate. remember that GPS is a line of sight navigation system and if you are in thick forest, or in a deep canyon, you may not get a signal. This usually is not a big deal. Simply climb to a high point,or get to a clearing and it works just fine, get your bearings and shut it off and hunt back to your destination.
hope this helps.

Just look at the Garmin line and pick what works best for you. I purchased a couple of Tom-Tom GPSs last year and they were confusing and difficult to use for me and my dad and brother. Replaced them with Garmins and they are much easier to use and have excellent features.

Let us know how it works out.

Jake

The Garmin etrex is all you'll need.

Thanks for the help guys. A Garmin it will be.
Jim

A great new safety tool for the outdoorsman is the Spot. It is a electronic device which can send your position to anyone you want via satellite. Besides tracking you it has the ability to send a "help" or a "I'm O.K." message to whomever you have programmed it to. It also has a button to send a "911" emergency request and your position will be forwarded to the appropriate responders. There is no voice, just three buttons. Simple and sure. It offers a high degree of security to anyone who is out in the country.

Check it out here: http://www.findmespot.com/en/. This is not a gimmick.

Joe, maybe we could get Mike one of those and bend it a little bit?

A question on GPSesssss.....

I have never owned one and only used a few in other people's cars.
Once you buy a GPS unit do you have to pay subscription fees for it's use (like XM/Sirius/DishTV/etc) or is the normal use free?

I imagine that software/map updates may be additional charge but I'm only talking the normal day to day use of them.

Lee, there is no charge for using GPS--it's in the public domain. Yes, map updates will cost a small amount.

good thing.

better not let the new batch of politicians hear about that. they will add hefty taxes/fees in the name of saving the environment. Probably find some way to add them to the propoesed Obama Cow Flatulance tax in the name of Global Warming.

Lee, Was that really necessary?

GPS was pretty much paid for in the 1980s out of the DoD's budget to the tune of 10 to 15 billion $US. The birds with those atomic clocks were launched just after the 1983 realization/model of the earth was calculated, viz. NAD(North American Datum)1983. And much new data was collected quickly for yet another realization, WSR84. Any rate, color just burns power and check for the Waas capablitity(give ellipses of error near 10 meters) which is land based correction from each coast on the North American continent. Works great when they are broadcasting accurate corrections. Have a look at the Rino com. devices also. I think Cabela's has them.

Kind Regards,

Raimey
rse

Italian SxS. I differ with the recommendations above regarding the Etrex by Garmin. It has a pretty minimal internal antenna and as I proved repeatedly this past summer even a single decidious tree will block it from receiving enough signal to operate. (I was on top of the highest ridge line in Pennsylvania but under trees this summer and the unit could not acquire enough signal to operate but my car mounted GPS functioned perfectly.) Oh yea, I didn't buy this one, a guy who got lost depending on it on the Kaibab gave it to me to use as a demonstrator in Hunter Education Class. In the desert where you have a totally unobstructed sky the Etrex is good enough if all you want is a set of way points to get you back. But get in any deeper and you will have to go hunt for open sky to get good readings. You get what you pay for and Garmin's upscale units like the Oregon 400T does just about everything and is much more user friendly. Of course it costs more too. Go to Sportsmans Warehouse or Cabelas or Bass Pro shop and have them demonstrated for you.

That's a good point on canopy(limbs only are canopy): it will not penetrate it. And when you do get data, it is corrupted by multipath. As far as antennas, if you don't have a external choke ring, you are not going to know the ground truth/correction postion with which to compare anyway. If you are within 10 meters you are doing excellent. Always hold the device as high as possible before saving a set of coordinates to get the best possible horizon.

Kind Regards,

Raimey
rse

I had an eTrex, and just sold it on ebay for about $90, and bought the Garmin 6oCx. I had two issues with the eTrex - the overhead canopy which has already been discussed, and the lack of memory to download large maps. The 60Cx solves both those problems. It's bigger, but far more capable

I'm no apologist for any company and am aware of canopy in acquiring signals. In my province canopy is not a problem during hunting season and rarely during fishing. Going in, taking a shot at lake- or road-side provides lots of sky. Just punch that waypoint when you're coming out. Fifty-foot or less accuracy from my inexpensive etrex Venture has been backing up my dead-reckoning for the last five years. Its repeatability to a waypoint has been as close as three to five metres.

Fifteen years ago, my son, chief pilot for McCain's, bought a $1,500 Garmin for the hell of it and attached an antenna with suction cup to a Falcon 50's side-window. The expensive inertial navigation systems were all over the place during oceanic travel. Approaching, Europe he asked Shannon for a report on the Garmin's positioning through the "gate." Dead-centre.

The basic Etrex is not map capable. It is a basic GPS. The canopy problem is horse hockey. I have had them since they came out, 3 iterations, and have never had a major problem. The newest one acuires satellites in seconds. I think some of the negative comments are being made from reading material, not practical use. I just bought and installed in my wifes car, a Garmin NUVI, now theres a system for the directionally handicapped..

It's according to what you are using it for. Regarding canopy and terrain, I can show you strings of noisy data that have multipath issues, but then again I use similar single frequencey units at about 5 times the cost with sub-cm capability which the average person hasn't any use for. Single frequency units are heavily affect by canopy and terrain. There's not another frequency for a check. When the data leaves the bird it has a time stamp. And when you catch it with your device, which is just a data logger, you know the time. Using both known time stamps and the speed of light, the distance from the birds to you can be calculated and a position also calcualted thru least squares adjustment with knowns and unknows equations. So a deflected/retarded signal from one bird, say on a 10 second data capture epoch, will put you at a seemingly longer distance and your position cannot be resolved.

By the way a second was added to the time to better model the Earth yesterday, which made it the longest day, which you wouldn't notice on a handheld 10m error of ellipse unit. If you haven't any accurate position to compare your position or check your device, you'll never know the difference.

Kind Regards,

Raimey
rse

That's pretty good Chuck. Now I guess I can't buy one for my new truck....darn.

BTW, Raimey seems to know waaaay too much about GPS to be a casual user.

Definitely comparable to his German gun knowledge!

I saw that Amazon has good prices for the mentioned Garmins. There is a new etrex
H version said to work very well in forests and canyons for USD88.50 plus shipping.

JC

Actually it is not. The satellites use microwave transmitters, around 1.2276 GHz, which is close to the radio frequency of hydrogen as defined by radio astronomers.

Microwave propagation is affected by several factors. One major inhibitor to propagation is absorbed by water. So in very heavy canopy during spring and summer there can be problems. Leaves after all have a heavy concentration of water. In fall and winter the reception will improve.

It is not much different than when some one using a satellite dish to view television losses signal during a heavy rain or snow storm. The microwaves are absorbed to the point the signal to noise ratio becomes unusable. With older gps units in the past I have experienced this both in Manitoba and northern Wisconsin. The angle of reception through the canopy is maximized. I assumed at the time that the signal loss was exceeding 20 db or greater in comparision to more southern locations lacking such heavy canopy and a higher angle of reception.

The systems Raimey uses are ultra accurate and capable of accuracy to within an inch or better, no were near the more gross consumer grade handheld accuracy. There has been improvement in recent years with the chip set, increased sensitivity. However, even the best commercial system can be impacted by absorption. I believe, but am not certain that only the military units can overcome this.

I have in the past done work in microwave frequencies up to and including 10 GHz. For a time, this was being considered for ultra wide band data transmission, fiber won the battle due in part to path loss issues.

Many handheld units use dual-conversion with a low-IF architecture. While this is conducive to preventing microchip architecture induced noise, it does restrict gain to about 95 dB and internal noise figures near 8 db. With low signal densities per mm^2 that 8 db does make a difference if path loss is increased by absorption.

Which to buy? The best you can afford. Your use will grow as you become familiar with the benefits.

Pete

Jerry Lape:
Would you please email me at italianstallion@cox.net
Jim

Chuck H: I meant that as a positive! The NUVI is so easy to use, and so accurate, thats its amazing. BUY ONE. On my old Martin Marietta briefcase is a sticky that says "Global Positioning Satellite System" Worked that project for a good while. We have come a long way since then. I used a plain old ETREX on my boat in Mexico and never needed anything more. I dunno what PeteM said....sounds like a Parker guy...Where have you been Chuck?

I bought a Garmin 45 when they were introduced about 15 years ago. Small handheld with a flip up external antenna, I did experience some canopy problems from time to time so about 12 years ago I bought a Garmin 12, same size but internal antenna and utilized 12 channels. Never had a problem with any canopy here in the NE at any time of year and I still use it today. No mapping, just coordinates, accuracy usually ranges around 10 yds. It still functions perfectly except it thinks it's July all year round. Time of day is always correct. Garmin no longer supports it so I can live with the day being off.

I still use the 45 while kayaking on LI Sound and as a backup for the Garmin GPS/Chartplotter on my fishing boat.

And I always carry a map and compass on land and water. I will practice coming back into port at night by compass to be ready for the day the GPS craps out.

Garmin makes the best units but they know it and are an arrogant company, they never admit to a problem. They'll replace a unit but rarely admit they have a production problem. A few years back they had a chartplotter, Model 198. Great unit for the boat except they had designed in a pressure equalizing valve that allowed moisture to enter the unit. The screens would fog up internally until the unit warmed up enough to dissipate it. I went through 3 of them, then they model was gone and replaced with a similar model sans valve.

Chuck H:

I guess I should know a little about receivers as I wrestle with them almost every day.

Jaycee:

As I've said before on the German stuff, I just have good sources, one being this board and I try to look at a lot of examples.

But back to the GPS on the topic of knowns and unknows, you need good data from a separate satellite for each unknown: Long., Latitude and height. Actually height is a demon all by itself that requires a specific constellation configuration for good values. We're spinning say at 1000 miles per hour and it's a complex, dynamic quantum system that looks as if it would never work. At any rate, due to the wavelength of light being near the nanometer range, there's a clock error, which of course is time dependent. So you need good data from 4 birds to get X, Y and Z. If you just have 4 you probably will be getting poor data from one. So more than 4 sources is always better and there are precise orbits which will predict the max number of birds for a given time. Actually in some cases, like on a body of water, X,Y position can be obtained from 3 satellites. Has anyone purchased or used the Rhinos(or seen the advertisment)?

Kind Regards,

Raimey
rse

A few minutes ago, when we sat down for breakfast, I noticed my wife had her Garmin NUVI out of her car, on the dining room table. She entered the daughters address in Boulder and said "I wonder how its going to route me". Well says I, you'll have to wait to find out till you get outside. It wont work in the center of a 2 story house, because of canopies, Mghz, Atomic seconds and waves and stuff...I know cuz thats what the xperts said! She pushed GO and it instantly showed her that she had to go out the driveway, down the road 1.2 miles and turn right...It also showed a full signal strength........

...go figure!!

JC

Another point of info I forgot to mention was that all Cell towers have Geodetic/GPS have positions on them. And after a engaged couple minutes, I don't know the exact length, if your position isn't known, it can be calculated. And the signal is out there for anyone to grab.

Kind Regards,

Raimey
rse