Navigation with GPS/watch?? Any thoughts experience?

adam0321

adam0321

Joined
Aug 20, 2009
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On this note, I just finished a day hike in TN. It was only a 1.6 mile loop hike and the area was surrounded by hard roads so I only brought my camera and a folder. I have a compass in my watch and had the trail guide (not really a map). I plugged the location of my truck in the GPS just for the sake of fun. When we were coming back to the car, I used the GPS just to see how accurate it was. If I had followed the GPS solely I would have been lost. It was pointing at one point almost 045m away from the truck.
So later I decided to play with the two GPS units I own. I placed a water bottle in a field and plugged it with both my Garmin Rhino and Garmin Map 60cs. They both read out the exact same 9 digit grid. Only the last digits were different. I then walked about 150 yards away and told the units to navigate to the bottle. One gave me a heading of 78DEG Mag the other 63 DEG Mag. I shot an azimuth to the bottle with my lensatic military compass and the bearing was 81 DEg Mag. One GPS told me I was 143M away the other said 137M. I began to walk towards the bottle and at one point about 85m out the units were pointing in opposite directions. Not off set from each other, more like on point 345m and the other 012m. They both said "arriving at bottle" about 21m away. While walking towards the bottle one GPS gave me a heading of 345m and the other 017m. the heading on my compass was roughly 005m. The rhino proved to be the more accurate of the two.
I have always used GPS units to simply find my location and then transfer that tot he map and use a protractor and compass to actually navigate.

Does any one navigate solely by GPS? I know it would get me to my about location but I thought the whole selling point of a GPS was to be able to find a particular leaf in the forest if you wanted to.

Also I own a casio pathfinder and a sunnto X6HR. Both read temp,alt, and have a compass. On any given day there is a 15 DEG difference in Temp, 20' difference in Alt, and 5-15 DEG difference in azimuth.

How reliable and accurate are these watches? I have always worn a analog watch with a clipper compass. I am trying to trust the electronics but it's tough.

Any experience thought on these issues??
 
I am an old guy and I never glommed onto GPS. Some people use it and love it. So I guess my opinion really is moot. IMHO, you are doing it the right way in not using it as a substitute for orientiering skills. Not everyone does. Like the ones mounted in cars getting people lost in the deserts and mountains. My brother uses GPS all the time and has since before it was available to civillians. A former Air Force pilot, he is a senior pilot for a major airline. He has devoted a lot of his time over the years to navigation calculations that would make my head swim.
 
First things first, did you match up the correct coordinate datum between the GPS and the Map?

Civilian grade GPS, ie. handhelds or vehicle based GPS units will get you "close" but are not exact. I have used them for numerous years and have never had an issue with them, but I know what to realistically expect. If one can get me to within 50' of what I am looking for, I can do the rest. The compasses on the GPS units are pretty pathetic generally speaking. In order for them to work properly, you have to be moving. Also depending on the unit, tree coverage can play havoc on them, especially the older ones. My 60csx is 1000 times better than the Etrex Vista that I started out with.

Now the GPS that I have used in the Land Surveying field can get you within a tenth of foot in the wide open, but then again they're thousands of dollars versus hundreds. Get close to a building or trees, and that $30k survey grade GPS unit just turned into a $100 Etrex.


Now using the watches, you do know that you have to calibrate them often, as well as your GPS units. It is recommended to calibrate them before every hike. The temp and altitude differences are because you are probably wearing the watch when getting the readings. To get the most out of the features you mention, you need to take the watch off of your body for 15 minutes or so and it will give a more accurate reading. The altimeter gets it's reading from Barometric Pressure, and you need to reset it each time you plan on using it. It will only remain accurate if the weather doesn't change and you don't have it close to your body.

I had a Suunto Vector that I took off my wrist and laid on a known BM while surveying, reset it to the actual elevation and checked it against another BM a couple hundred feet higher up the hill, and found that it was within 5' of the actual elevation. That's plenty accurate enough to find myself on a map.
 
I was not using a map. I simply used them in a open field. I was only testing the units for fun. I to got spoiled by the $$$$$ military units we have. I do calibrate the units often. And when I was checking them I had left them on the porch overnight and checked them in the morning.

I find it funny that a tool to measure weather only works well with little to no weather changes.
 
I don't know what the problem is then if you didn't use a map, which would do away with any possibility of crossing up your coordinate datum. I have used my 60csx quiet a bit while surveying. It is plenty accurate enough for me to flag clearing limits, get reasonably close to monuments, and even doing area summaries on properties. That being said, I would never fully depend on it or anything else that requires batteries.
 
adam0321 said:
Does any one navigate solely by GPS? I know it would get me to my about location but I thought the whole selling point of a GPS was to be able to find a particular leaf in the forest if you wanted to.
Click to expand...

I never navigated solely by GPS, ive always used one with a map and compass. That being said, ive tested my GPS on several occasions and found it accurate down to a couple of yards. The waypoint bearings it provides are accurate too, although you have to be moving to get an accurate reading. Same thing with the GPS compass. I own a Garmin eTrex H.

adam0321 said:
Also I own a casio pathfinder and a sunnto X6HR. Both read temp,alt, and have a compass. On any given day there is a 15 DEG difference in Temp, 20' difference in Alt, and 5-15 DEG difference in azimuth.

How reliable and accurate are these watches? I have always worn a analog watch with a clipper compass. I am trying to trust the electronics but it's tough.

Any experience thought on these issues??
Click to expand...

I belive the watches to be very accurate, provided they are calibrated correctly. Ive owned a Suunto Vector, Casio PRG-40 and i currently own a Casio PRG-240.

The barometers have always been precise (with in a point or two), when double-checking with the national weather service. The baro graph shows air pressure rise/falls and is 100 procent sure to predict a low-pressure system coming in.

The altimeters are influenced by air pressure and temperature variations, so this is the least accurate function. But if you understand how the airpressure influence it, then it can be very precise. Ive used my Casio altimeter readings when hiking, and theyve been accurate down to +/- 5 meters. Of course, i did a manual calibration at a known altitude and kept it a my wrist for a stable temp.

The compass on both my Casios have been spot on. I once compared all my compasses back to back, and the least accurate one, was the button compass in the ESEE fire kit. Ive also owned a Recta watchband compass...that thing was so inaccurate, that i took it off and never put it back on. My 2 Casios were within a couple of degrees of my Silva.

My Suunto compass was horrible..It was consistently off by about 30 degrees, no matter how many times i calibrated it. I believe a factory calibration would have sorted it out. After my Vector, i went Casio and never looked back.

Regarding the temp readings...You need to take the watch off your wrist and leave it for about 20-30 mins, then youll get a an accurate reading. Otherwise your bodyheat will cause it to give a higer reading than it actually is. The manual also states this.

I trust Casios Protrek/Pathfinder watches... As i said, if you know how they work and know their limitations, you'll find them very accurate.

adam0321 said:
I find it funny that a tool to measure weather only works well with little to no weather changes.
Click to expand...

An analog baro/altimeter works on exactly the same principle.
 
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