A GPS unit

[dinora_de_rivera]

<p>Can anybody tell me where could I find a GPS unit that I can carry in my pocket, which will show me the geographical coördinates, altitude above mean sea level and which is very precise, showing me the coördinates in decimal angular secondr?</p>

<p>Does, for example, Garmin have one?</p>

<p>Or any other manufacturer?</p>

[Spearhead]

<p>If you have a smartphone, there are plenty of apps that can do this. An Android app can be found <a href="https://play.google.com/store/apps/details?id=com.mygpscoordinates&hl=en">here</a>. An iPhone app can be found <a href="https://itunes.apple.com/us/app/gps-location/id353474465">here</a>. There are others, just search.</p>

[charles_stobbs3]

Don't cell phone location systems depend on being in a place where there is are cell phone signals?

[geoffs1]

Most phones have a built-in GPS receiver (a

lot of them can also use the Russian

GLONASS system too).

[AlanKlein]

<p>What do you want to use it for? On the water? In the woods? In urban areaas? </p>

<p>Assuming you will be in remote areas, you'd want one that is reliable. Garmin has excellent units. I've been using them in the woods since 2001. Some come with street maps, some with topos showing elevations, etc. All provide coordinates, simple ways to mark waypoints and locations, ability to transfer info to the maps in your computer, etc. Some provide altitudes based on the GPS satillites. Other provide a pressure sensor that measures altitude and have to be calibrated. Some provide 3 axis compasses rather than depend on the GPS satellites. Check their web page for the features you want.<a href="https://buy.garmin.com/en-US/US/on-the-trail/handhelds/cOnTheTrail-cHandheld-p0.html">https://buy.garmin.com/en-US/US/on-the-trail/handhelds/cOnTheTrail-cHandheld-p0.html</a> </p>

<p>Always take extra batteries with you. Mark your car before you go into the woods before so you can find your way out. Practice using the GPS at home before using in remote places. Do not use you cell phone. I have one and while it works, it's unreliable. Also, it stops working once the battery goes dead which is fast. Dedicated GPS's last longer on a battery.</p>

[bobatkins]

<p>Garmin have lots <a href="https://buy.garmin.com/en-US/US/on-the-trail/handhelds/cOnTheTrail-cHandheld-p1.html">https://buy.garmin.com/en-US/US/on-the-trail/handhelds/cOnTheTrail-cHandheld-p1.html</a> though whether they all will display decimal degrees I don't know, but I imagine they all probably do. My 10 year old Garmin etrex has about a dozen options for location display, including decimal degrees, degrees and decimal minutes, degrees-minutes and decimal seconds etc.</p>

<p>To be sure you probably need to download the product manuals and check.</p>

<p> </p>

<h1> </h1>

[AlanKlein]

<p>Shop on-line. Alot of these units are discounted under what Garmin shows as their pricing.</p>

[Edwin Barkdoll]

I've had several Garmin GPS units including one that allows me to track my dogs - very handy.

 

That said unless I'm in the middle of nowhere and need to track my dogs I use my iPhone and GaiaGPS, or some other

app, exclusively (unless there is a good chance of dropping it in the ocean,lake...). And even when I use the Garmin to

track my dogs I almost always use my iphone at the same time for making a track adding waypoints etc.

 

The main reason is ease of use.

The Garmin software, compared to a smart phone with a good GPS app, is atrocious. Many functions that I would like to

access quickly are nested deep in unmemorable menus. Furthermore, detailed topographic maps from Garmin are not

inexpensive and some formats do not play well with Garmins desktop software. In fact getting the data on my Garmin

handheld onto my computer can take 20 minutes or more. This is unacceptable and I end up never using the desktop

software.

 

Adding and naming waypoints, editing, importing and exporting tracks, viewing differrent map types (eg Topo vs satellite)

are all trivial on a smartphone/app combo but are at best a pain and at worst simply cannot be done on the Garmin.

[Edwin Barkdoll]

And like Geoff said most cell phone these days have a gps module. Most of the time that I use my phone for GPS I have

no cellular signal whatsoever and get a great GPS signal.

[MichaelChang]

<blockquote>

<p><em>"which is very precise" </em><br /></p>

</blockquote>

<p>The required level of accuracy might determine your choice, or might be beyond currently available technology. </p>

[AlanKlein]

<p>Edwin: I don't understand all the problems you're having with Garmin. I don;t have those problems. Are you using their Mapsourse computer program that allows easy transfer all all waypoints, tracks and other info both ways. You could then see all the info on both the GPS and computer with all that info very easy. </p>

<p>The Gaia alternative sounds interesting for using when you're not in the back woods. I'd bee hesitent to use my smartphone that goes dead with low battery use and has no protection against rain and dropping ojn rocks. Does Gaia have an altimeter? Can you enter multiple waypoints to creat a track? Can you switch to a regular map so that yoou can get driving directions? </p>

<p> </p>

[Brad_]

For precision (2.5 meters) and a sensitive and WAAS enabled receiver, consider a <a href= "http://bad-elf.com/pages/be-gps-2200-detail">Bad Elf</a>. Also reports velocity up to 1,000 MPH, in case you need to go

supersonic. It's also a great logger/tracker (updating up to 10 points per second), and keeps the drain off your phone's batteries. I have one and it works great.

[Edwin Barkdoll]

<p>The problem with the Garmins I have is as I've described - primarily with the units cumbersome software. For example if I want to name a waypoint on the Garmin, say, "Bearded Tooth LLP Acadia on tree over stream (little)" I would have to hit Enter over 50 times and the arrow buttons 150 times or more to navigate around the keyboard to choose the characters.</p>

<p>There are newer touchscreen Garmins, which I've not upgraded to since I have no need at this point given other readily available options (and for a lot less than $500), hopefully they resolve these issues. However, they do not resolve Garmins inability to readily import free, non-proprietary, worldwide maps. Prior to a trip to Ecuador a couple of years ago I downloaded a topo map of the area in a few minutes.</p>

<p>As for being in the "back woods" I am in them every week more than once. I have never run out of power with my phone - just as with my Garmin, I take back up power.</p>

<p>I'm not anti-Garmin I just think if someone already has a smartphone they should think hard about whether they need a dedicated GPS.</p>

[Edwin Barkdoll]

<p>And yes you can enter multiple waypoints to create a route, yes it has an altimeter, yes you can switch to a regular map (it's a smart phone... You can even get Garmins Navigation app if you want).</p>

<p>As for protection, get a good case.</p>

[Ian Taylor]

<p>I have an old 60 series Garmin, I use it for everything - cities, road trips, 500+ km kayak trips etc. Garmin is a great company with excellent service. I would have a good look at all their range and find something. They make a lot of sales on their maps, I use a few of their marine charts, but for everyday stuff you can build for free from open source maps.</p>

[AlanKlein]

<p>I'll check into GAIA; seems like a nice program. For what it's worth, I also have open sourse maps in my Etrex that gives me 24k topos for the entire east coast. I've loaded them into NUVI's car navigation units as well as my Etrex. </p>

<p>Another program I recently added which is good for us photgraphers is The Photographers Ephemeris. (TPE) It shows the direction of the sun and moon on the desktop or cell phone including rise and settings times of the sun and moon, angle to the horizon and azimuth on the compass so you know in advance where the sun or moon is going to pop up or set.. Very handy for planning "good light" angles to know where the sun and moon will be.</p>

[dave_s]

<p>You can probably get the most useful advice if you go to websites which are geared to your specific activity need-- like for example, if you're a backpacker, a climber, or an off-road 4WD guy. </p>

<p>I recently had to make the same decision prior to a backpacking trip in Utah. I *almost* bought a <a href="http://www.rei.com/product/825491/garmin-etrex-20-gps">Garmin etrex 20</a>, which you can get for about $180 from REI or similar retailers. This unit gets reviewed well by backpackers, and it delivers a lot of value for its price point. If I needed a dedicated GPS unit, that's what I'd go for, along with a set of spare AA cells. For your purposes, if you need a serious altimeter (I don't), the <a href="http://www.rei.com/product/825492/">etrex 30</a> ($270) has a pressure-based barometric altimeter and other features.</p>

<p>When the dust cleared, I decided not to carry a separate GPS receiver. I simply updated my phone to a Samsung 4S, and got an app called <a href="https://play.google.com/store/apps/details?id=com.crittermap.backcountrynavigator.license&hl=en">Backcountry Navigator</a>. While there are a bunch of GPS programs out there, Backcountry Navigator seems to be the favorite of most backcountry users. You can test drive a demo version for 30 days for free, but you might as well just buy the better 'Pro' version up front (about $10).</p>

<p>The Samsung 4S + Backcountry Navigator combination worked great for my purposes. I could easily get a GPS fix with the phone in airplane mode, when I was way out of range of any cell tower. (Not all cellphones will do this, and some of them have to have the phone reception on until they get a fix. The makers of Backcountry Navigator make a free app called 'Airtime' which provides a workaround for this.) </p>

<p>The smartphone was not as fast as a dedicated GPS unit, and it would generally take a minute or two to pinpoint my location, with the phone in airplane mode. It was right on the button and there were no errors or failures. </p>

<p>Backcountry Navigator works with free maps that you can download from the internet, including large scale maps like the USGS 1:24K series. You can also subscribe to Accuterra maps, which are very slick, but that service costs twenty or thirty bucks a year.</p>

<p>Long answer to a simple question, but in the end, it comes down to whether you need a stand-alone GPS unit. A lot of backpackers seem to be just using their smartphones now. It means you're carrying a single device, it's light in weight, and it serves multiple functions.<br>

</p>

<p> </p>

[AlanKlein]

<p>Dave: I just happen to have a Samsung 4S so I'm very interested. How do you deal with battery issues? DO you have any problems mwith your compass losing its calibration?<br>

As an aside, my S4 has compass problems. I have to keep calibrating it. I have two programs that rely on the compass that both won't work right because of this problem until I recalibrate which doesn't always work. (The satellite GPS info still works however.) I understand its a known problem with the cellphone that hasn't been fixed yet. This is one of the reasons I would not recommend anyone use a cellphone for serious back woods hiking. Battery re-charging issues, functional problems depending on your cellphone that you won't know about until you get lost in the woods and the unit stops working, drop and waterproof issues, etc. They're OK for urban and run around in local parks where every way leads to a street. But I would not use in the woods for any half serious navigating especially if you're new to these things. </p>

[dinora_de_rivera]

<p>Thank you, everyone, great replies!</p>

<p>I am struck that even though I've used the navigation app in my phone (and hated it), I never thought that there could be a GPS app somewhere out there. But – d'oh. </p>

<p>However, yes, I would need a stand-alone, handheld device. So I'm checking some of the mentioned Garmin devices and they all have a barometer altimeter.</p>

<p>Why on earth is that? I thought it would be easy for the satellite also to provide the altitude information, but it seems it isn't so. Why rely on a barometer? It's kind of tricky, given that pressure is dependent on the lapse rate, and the lapse rate on humidity and some other factors, to calculate it that way. On the other hand, I guess these people should know what they're doing and it should be fairly precise.</p>

<p>I wonder if I could find the accuracy information in some Garmin brochure or something like that, the detailed technical specification.</p>

[dinora_de_rivera]

<p>Oops!</p>

 

<blockquote>

<p>Global Positioning System (GPS) receivers can also determine altitude by trilateration with four or more satellites. In aircraft, altitude determined using autonomous GPS is not precise or accurate enough to supersede the pressure altimeter without using some method of augmentation. In hiking and climbing, it is not uncommon to find that the altitude measured by GPS is off by as much as a thousand meters,<em>[citation needed]</em> if all the available satellites happen to be close to the horizon.</p>

</blockquote>

<p>How do the geodesist determine the elevation of a point?</p>

[dave_s]

<p>Alan, all good points. Here is the way I approached them.</p>

<p>(a) This was only a five-day photo trip with me and my Rolleiflex through the west side of Zion Park-- no remote Antarctic expedition or anything. Battery life was not an issue. I kept the phone powered off, and turned it on to horse around with the GPS maybe one to three times a day. When I had the phone on, it was in airplane mode, so it didn't run down the battery looking for a cell tower. By doing this, the phone used almost no power and I had over 85% of a full charge at the end of five days. (Hard to say exactly how much the GPS used, because on the second last day I made a couple of phone calls and texts when I had a signal.) </p>

<p>(b) I didn't use the compass function on the phone. I carried my Silva Ranger for that, and printouts of the 1:24k topos. Paper maps are, obviously, far superior to anything you can see on a little tiny screen.</p>

<p>© Waterproofness: <a href="http://www.lifeproof.com/shop/us_en/fre-samsung-galaxy-s4-case/">Lifeproof case</a>. This is an important one for me, because I tend to drown cellphones (and cameras).</p>

<p>(d) I should add that I never really *needed* the GPS, and a map and compass were all I needed. The trail was mostly easy and obvious, but there were two occasions when the GPS came in handy as a check. </p>

<p>Having said that, I understand one of the classic ways for inexperienced canyoneers to lose their lives is to make a wrong turn and descend the wrong canyon. If I was doing anything like canyon descents in unfamiliar country and my life depended on it, I'd just blow a couple of hundred bucks and get a dedicated GPS unit. I should add that I carry an <a href="http://www.acrartex.com/products/catalog/personal-locator-beacons/resqlink-plb/">ACR ResQLink</a> now, too-- I'm not getting any younger.</p>

[AlanKlein]

<p>Dinora: The issue with using the GPS for altitude, is that there may not be a clear view of 4 satellites. You need the forth for altitude and only three for location coordinates. You're right that weather effects the pressure and therefore the altitude reading. But you can calibrate it to either the GPS height while you are in a clear area. Or you can put in the actual altitudeif you know what it is. SUch as a previous determination of what altitude your home is. You set that before you leave. Or, looking a a topo map and then seetting it to the location you are currently at. The pressure port reading will adjust to the local barametric value. One other advantage of the pressure reading over the GPS calculation, is that some people use it as a barametric instrument that you can see a plot over time showing not only the elevation track, but also barametric for change of weather. Handy if you're up in the mountains and where are quick changes in weather. </p>

<p>The Garmin 30 also comes with an three-point compass in addition to the pressure sensor. The advantage is that you can determine direction from a stand still like any other compass. Units like the Garmin 20 use your moving from one location to another to determine compass headings based on changes from the GPS satellites. GPS systems cannot determine direction your facing, only location at some spot in the world. That can be confusing to a GPS especially if you're on a boat or frankly just standing there.</p>

<p>If you have the money, go for the 30 or something similar. </p>

 

[AlanKlein]

<p>Dave That ACR unit looks pretty good especailly at that price point. I could think of a few times I thought I was really lost and started to panic. Haven't that unit would have worked but I'm sure I would have been embarrassed after they found me. Fortunately I got myself out before I froze to death.</p>

<p>Those were in the early days when the GPS devices would lose the satellite signal under heavy tree canopy. Fortunately, the ones today are better. The other mistake I've done on more than one occassion is to forget to mark in the unit where I parked. So finding my way out became more difficult. Fortunatly, the track made it relatively easy to follow. That's another good reason for a dedicated GPS. You can leve it one the whiole time and not worry about battery dropping dead. Well, that was the other times I had a problem. When the GPS did go dead and I didn't take any spares. </p>

[User_1172872]

<p>My Olympus Tough digital camera has a GPS. Uses barometric pressure to determine altitude. [Whether that's more accurate than a GPS handheld device I don't know.] Plus, it's waterproof to 50' and shock-resistant so for me it's perfect for hiking - no worries about it getting soaked - and when I take a picture of the trail the GPS coordinates are in the EXIF data. Other companies make similar cameras, have a look at dpreview.com if you think the waterproof camera/GPS option might work for you.</p>

[MichaelChang]

<blockquote>

<p><em>"How do the geodesist determine the elevation of a point?"</em></p>

</blockquote>

<p>There are many Internet resources describing the problem, and it usually begins with the question "What is sea level" when the earth approximates an ellipse and there are vast landmass areas where no ocean exists while ocean levels are affected daily by the moon's gravity. <br>

<br>

GPS systems use the <a href="https://www.google.ca/search?q=WGS+84&espv=210&es_sm=122&source=lnms&tbm=isch&sa=X&ei=2hGUUv_ZE_GCyAGJ74CwBQ&ved=0CAkQ_AUoAQ&biw=1440&bih=769#facrc=_&imgdii=_&imgrc=xpvW7fMAkEpyPM%3A%3BLxrAZ4hzH9950M%3Bhttp%253A%252F%252Fwww.pha.jhu.edu%252F~hanish%252Fww15mgh2.gif%3Bhttp%253A%252F%252Fwww.pha.jhu.edu%252F~hanish%252Fseminarmain.html%3B1025%3B636">earth's gravitational map</a> to determine relative altitude based on the World Geodetic System, WGS 84:<br>

<a href="http://en.wikipedia.org/wiki/World_Geodetic_System">http://en.wikipedia.org/wiki/World_Geodetic_System</a> <br>

<br>

The problem of absolute altitude measurement is further compounded by satellite location and a particular receiver's susceptibility to multipath signals which can dramatically increase measurement error. Geodisists typically use professional grade GPS units to minimize various contributors to cumulative errors which can cost many thousands of dollars. <br>

<br>

I've all but given up on altitude measurement when I tried to obtain a meaningful GPS reading while setting up a TV antenna relative to the stated transmitter altitude about 100 miles away. For recreational use, however, typical consumer grade GPS are probably more than adequate for relative measurements on personal travels. </p>