need gps advice

Cloudy weather has no effect on GPS, so you are dreaming.

Apparently you are not aware that GPS was developed for precision military navigation. Do you think that the military stops its operations because of clouds? I think not.

–B.G.–

Cloud cover doesn't affect GPS performance

If you're walking in deep canyons then the improved antenae of 60CSx and other more expensive GPSes is useful.

Even with cheaper GPSes, they'll work in more open area. In canyons they'll lose lock some of the time and work some of the time.

It's also effected by how many satellites are currently "visible" which varies over the day, and over time – occasionally a GPS satelite dies and occasionally new ones are launched.

If all you want to afford is an e-trex, then buy it.

Maybe you can buy one used? Look a gear swap or post a request on gear swap

Its true. My Garmin eTrex Vista does not acquire signal on cloudy overcast days. It doesn't make sense but others have reported this weird phenomenon. In contrast my TomTom car GPS does not have this issue, but possibly due to the better built in antenna.

If your Garmin doesn't receive a signal on a cloudy day, then it is defective. Throw it away and get a normal one that works.

Now, a different issue is rain water. As long as the rain drops are falling from the sky, GPS still works. If you allow rain drops to puddle on top of the antenna, then that could block the 1.57G signal. However, wiping rain drops off the antenna isn't much of a job.

Your car receiver probably never gets rain drops directly on the antenna because they are out on the windshield.

So, this may be a user error.

–B.G.–

Bob, I don't own a gps so, no, I'm not dreaming, just asking…somehow I doubt that the military is using $100.00 etrex to navigate its fighter jets. Seems reasonable that a cheaper device may not function as well as military grade hardware, but as stated, I don't know. Hence, the post. But it's good to hear that 2 out of 3 say that cloud cover is irrelevant. I'd prefer the cheaper unit. Any more opinions/observations?

OK. Military fighter jets use a military grade GPS receiver. That means that it receives signals on both the standard L1 frequency and also the encrypted L2 frequency. As a result, it works with a little better accuracy than a straight L1 civilian receiver. It is awfully hard to find any hiker who needs that accuracy. The mil-spec receiver can also update faster, can operate to speeds faster than Mach 1, and can operate to extremely high elevations. Find me a hiker who needs all that.

I always buy L1 receivers that can handle an external antenna, whether I am actually using the external antenna or not. The external antenna is extra cost, and it uses extra power. However, there are times when the external antenna comes in very handy, like for in-car use. Most hikers don't care.

I used to advise and assist my customers install permanent GPS receivers in buildings with permanent GPS antennas on the roof. GPS is Not just about navigation.

Believe me, weather is not an issue, except for possibly a nearby or direct lightning strike. But then, a hiker would be a crispy critter after that.

–B.G.–

p.s.Bob I just read your trip report. I like that loop a lot! but it's a roller coaster for sure.

I'm not sure that roller coaster is the best term. More like a seesaw.

Everybody was doing that loop in a clockwise direction, and I'm not sure that it would be any better. With the exception of one trail runner, nobody was overtaking me going anticlockwise. Everybody that I met was doing the loop in 6+ days.

One way or the other, you need helium inserts for the side pockets on your backpack.

–B.G.–

Re: "I need a gps for day hike snow shoe trips. Mostly I want a bread-crumb function"

Puzzled: Why would you need a GPS for bread crumb function for snowshoeing, when you have your snowshoe tracks?

I do not want to use a GPS for bread crumb fuction, but to help with navigation to points represented by UTM coordinates taken from maps.

Several problems have occurred:

>The earlier model hiker GPS's took so long to activate that I stopped using them.

>It took forever to input waypoints into the GPS, by marking current location, and then editing to get the desired waypoint. None of the instructions were at all helpful in this process, so it was necessary to use trial and error with each model.

>The instructions say that with most models you have to be moving for the GPS pointer to work. No way am I going to be looking anywhere when moving except where I'm stepping/going.

Is there a publication out there that addressed these issues in detail?
Would appreciate any help.
Thanks.

…

OK, GPS Newbies, listen up.

The early generation of GPS receivers (c.1994 and before) were single channel receivers, sequentially multiplexed. That meant that it might take as much as five or ten minutes for TTFF (Time To First Fix). The next generation (c.1997) were much faster, and had multiple parallel channels for reception, so the TTFF dropped significantly to be large fractions of one minute. There were some moderate improvements in receiver design in the 2000-2004 era, and then SIRF chipset receivers came on the market which had hundreds of parallel digital correlators. That sped up the TTFF process also. Along the way, great improvements in the map databases and displays have happened. However, in my opinion, there is no way that the small screen display can show you the level of mapping detail as a good paper map.

">It took forever to input waypoints into the GPS, by marking current location, and then editing to get the desired waypoint."

I guess you know now that none of that is necessary, at least not for the last 15 years. There is software that manages waypoints quite nicely, and then you transfer that waypoint file to the receiver. A few old receivers have no data transfer capability, so you are stuck.

">The instructions say that with most models you have to be moving for the GPS pointer to work."

That is true on most receivers. The exceptions are those strange models that have a built-in fluxgate compass. Most receivers have no idea at all about what direction you are facing when stopped. But, they will know what its position is, and if they detect a new position a second later, and another new position a second after that, it can _infer_ what direction you are headed. Based on the current position and based on your intended destination, it can _infer_ what direction you need to move to get there. Note that the direction might be practically stupid, because a direct route might be bad. That is where a terrain-thinking individual will beat the GPS receiver.

There are more GPS publications out there than you can imagine. Some are single-model specific. Others support the mapping software for your computer for waypoint management. Every brand and model of receiver is a little different, so there is no single book that teaches everything.

I taught GPS classes in industry for about 15 years.

–B.G.–

I was climbing Mount Washington, New Hampshire, and it was winter with snow on the ground. Although I had studied the map, I knew that visibility can close in and leave you with no visible landmarks at all, which is why lots of climbers die up there. So, I took my trusty old Garmin GPS12XL receiver. However, I did not want to walk along holding this thing out in front of me with the patch antenna pointing up. So, I stuck the receiver inside my parka inner pocket and ran the cable up my neck to the external antenna stuck between my inner hat and my outer hat. That way, the antenna was always pointed up. To offset the additional power use, I loaded it with lithium primary batteries.

The old quad helix antenna (Garmin and Magellan, c.1994) was much better for mitigating multipath interference, like noise from the horizon. After a while, that was thought to be less important, so the quad helix died out and the patch antennas took over, partly because they were much less expensive to make and less likely to break. If you have ever taken apart a quad helix, you would be impressed.

–B.G.–

Thanks for all the responses. Why breadcrumbs in snow? good point; sometimes it snows very hard and tracks can be obscured over several hours. Also I'm known to wander off. Frankly I don't like devices much and just want something simple to help out if it starts to snow hard and visibility becomes a problem. That's why the curiosity about performance in snow/cloud conditions. But I'm not going to rely solely on a gps or anything.

Google “GPS Clouds signal”

Half the hits are people asking why their device (Garmin, Magellan, etc) has poor reception under cloud cover.

The other half are product vendors and pseudo-science people quoting the documentation that clouds are not a factor to poor (or no) signal under cloud cover.

My Garmin eTrex is not defective, it works great on sunny and partly cloudy days.

I agree that it “should work” under dense clouds.

My experience is that it doesn’t work under dense clouds.

Many MANY others report similar experiences with various consumer grade handheld GPS.

The closest voodoo logic is that the signal is diminished greatly if wet or under water. So the voodoo logic is that “dense fog or clouds” forms a thick layer of water vapor, causing the GPS device to receive very weak signal that it times-out the search to triangular the satellites.

Individually, vendor support will argue with you to make you believe your signal is weak because you are in a canyon, cave, submarine or scubadiving, after a while you might doubt yourself and believe that you were not on a summit ridge, and that your situation is isolated, unusual, and that it must be user-error (your fault somehow)

Fact still remains – many people with various handheld GPS consumer grade device models, consistently report weak signal with direct line of sight in open spaces, under cloud cover.

Google "User Training Issue".

The signal arriving from space is "way down in the mud," to use a technical term. The spread spectrum signal is actually lower than the noise floor. I know that sounds like an impossible situation to overcome. However, it still works.

In the military version, the two downlink frequencies travel along, but are absorbed slightly differently in space. This difference is known, and that extra bit of knowledge is fed back up and then back down to the receiver. So, the atmospherics are "bucked out." It is still a pretty slight difference that the civilian models can't adjust for.

Most users would not understand multipath interference if they stared it in the face. If you are deep within a narrow canyon, first you might have a very limited view of the sky, and the receivers won't get a fix without a minimum number of birds in view. Secondly, and especially if that narrow canyon happens to have lots of large reflective surfaces (e.g. skyscrapers, flat rock, metal towers), then the downlink signal might bounce off a time or two before hitting the actual antenna element. Since the signal is right hand circularly polarized, when it bounces it becomes a left hand circularly polarized signal, so one bird's signal gets cancelled out temporarily. That's what happens when the user thinks that the signal must be weak. Instead, put that on a spectrum analyzer and see what you have. Now, if multipath is a suspected problem, then get rid of the patch antenna and move up to a quad helix. Or, if price is no object, move up to a choke ring antenna. Just remember to bring along a wheelbarrow to move it.

If you have some water vapor in the atmosphere, it doesn't have much effect on reception, until you get to the point where the water vapor is condensing. Then, if all of the signals are trying to slice through the same rain cloud, things could be hit or miss. But, what are the chances of that? Liquid water on the antenna could be a problem.

An interesting exercise is this. Many receiver will show you a satellite view display. This shows where the birds are supposed to be located overhead at that very moment. Then the icons change from one type to another to show you if the downlink signals from each bird are actively received or not. Then look up from the display and look at the sky. You may find that the "missing birds" are temporarily behind a tree or otherwise obscured.

In the early days of GPS, there weren't so many birds up, so the "defective downlink" allegations were rampant. Once the constellation was fleshed out, most of the allegations went away. If you think you have a real satellite signal failure, you can report it to the U.S. government. Good luck with that.

There is another thing that is pretty cool to watch. It is called a GPS Blunder. The way a receiver works (which actually has nothing to do with triangulation; maybe trilateralization) is by measuring the times of signal arrival between one bird and another and another. Using heuristics (guesswork), it knows that there are two solutions for the PVT (position, velocity, time) at the receiver. Then it guesses which one of the two solutions makes the best sense, because one is typically out remotely in space, and the other is typically within a few hundred miles of where it last had a fix. So, it takes a stab and displays the PVT result. Surprise! Once in a while, the guess is wrong (a GPS Blunder) and it displays something that is almost totally bogus, like that you are 25 miles away from your true position, and you are moving along at 40,000 feet elevation and going 400 miles per hour. If you are a hiker with those kinds of numbers, then you (the human user) should know that it is a temporarily bogus solution. If you watch it long enough, sometimes the receiver will demand that the user shut it down and reinitialize. Normally, I just shut it down myself, and when it starts back up again, the blunder will be gone. I believe that I've seen seven blunders since 1994, but I have seen many more reception anomalies that I reported to the Federal Communications Commission as a case of "rogue microwave transmitter" somewhere in the near field. That 1.57GHz is a protected band.

I met the guy who was the GPS project manager at Rockwell when they first said, "Let's have GPS." He had GPS war stories that would curl your hair.

If you don't like the answers, then throw away the receiver and go back to using a compass.

–B.G.–

TWO Fact still remains:

#1) Many people experience and report that GPS devices fail under dense cloud cover in open spaces.

#2) Vendors, manufacturers, manual readers reject fact #1, without explanation of why #1 is happening.

Rodney, please follow the last line of my last message.

Just because people allege that the receiver is failing, that doesn't mean that the receiver is failing. That might mean that the receiver is unable to resolve the PVT solution, but you don't know why that is the case. It could be one of a dozen things from the U.S. Air Force Space Command to the birds to the atmosphere to the receiver to the user's interpretation of what is going on. Just because the user can't understand how this works, it doesn't mean that it isn't working.

Google "GPS and sunspots."

There is an Air Force document of several hundred pages that explains all of this. The first time any of us read it, our heads were spinning. After studying it a few times, it slowly starts to sink in. The receiver vendors all have copies, but I don't believe that they ever release it to the civilian public.

There is a civilian agency that is set up to field questions from the civilian public, especially for commercial/transportation GPS purposes. I've been in meetings where they tried to field questions from some very large telecom companies about why this and why that. After ten minutes of argument, some cause/theory is settled upon. When you are a very large telecom company that is completely dependent on GPS for your network synchronization, and then when that goes away for a moment, it is rather like pouring large garbage cans full of hundred dollar bills down the drain every second. It's all quite exciting, ain't it?

–B.G.–

The experience i had on the CDT was that people that relied on GPS as a primary means of navigation were let down at some point.
A paper map and a magnetic compass NEVER fail.
The high techery is a great backup, but should it fail and we are not are "on" our maps it becomes very difficult to "find" your position on the map.
Nothing like a good compass and map kid.

Matt, you are absolutely right. Any battery-operated electronic device is likely to fail, sooner or later.

My newest GPS receiver (2 years old) just completely crapped out about one week ago, and it seems like it is power-related because it is completely dead.

–B.G.–

I met Nomad, a United States Navy Veteran and Nagivation Specialist on the CDT. He was doing trail support for his wife. His newly bought GPS unit had just "crapped" out on him.
He asked me what i was using.
I produced my Jonathan Ley paper map; laser printed on 8.5 X 11 inch plain paper and the Suunto M2 compass on the lanyard around my neck (ALWAYS!). Nomad told me: "THAT is bombproof technology!"
I had a GPS fully loaded with CDT data sitting in a resupply box back home in California at the time.
After seeing the troubles of others and my conversation with Nomad there in New Mexico, I had the GPS thrown out of my boxes.. and my plans.
I am not a GPS hater.
I think if it is used as a backup device it is great.
The problem is; nobody uses it as a backup.
Folks I met were using the GPS, and then AFTER it failed, they would fall back on their paper maps.
Not having the familiarity, or dare I say.. skill with paper map and compass navigation they were at a significant dis-advantage.
Despite what the well meaning locals will tell you.. the compass needle never spins in the Anaconda Pintler.. or anywhere else you aren't standing too close to a hunk of steel like a cattle fence. And even then it is only deflected. It's pretty simple common sense really.
"That little needle works day and night, in fog and rain, in cold and heat, and never needs batteries."- Nomad
I knew i had made the right choice after i spoke to him.
Global positioning systems are cute. They are nice toys. They are NOT replacements for true navigational tools.
Yes, the military uses them but even they require a backup system.. the map and compass.
The major dis-advantage i see form GPS based recievers is the lack of scale.
You have this tiny screen and you scale the data up and down but you never get the whole picture of where you are or the scale of the enviroment you are in.
A properly scaled paper map tells you what you need to know so long as light is reflected off it's surface and you can keep the paper intact(ziplock).
Yea, i got "misplaced" or lost plenty of times. I vowed never to turn back also. i always found my way with my paper map and compass.
"Nothing like a good blaster (map and compass) at your side kid".- Han Solo

Thank you for the info related to my post.
Looks like a 'personal GPS trainer' is going to be required.

I used to be able to hit waypoints dead on with a decent map and compass; but for some reason, the skill diminished with age. Didn't know what to make of it; then this summer, met a rancher from Eastern Colorado about my age who has had the same experience. It may be related to the number of variables one can juggle in the head, and how that is affected by age. Or perhaps it is an inner ear issue.

In any event, as usual the answer is to replace natural abililty diminished by age with technology. It really would be nice to be able to turn on the tool, and get a quick point exactly in the direction of a critical waypoint (Like where to leave the highlands and descend below timberline; or where a 'trail', as with many abandoned by the USFS, crosses a stream).

In this connection (diminished capacity), would be interested to know if the Garmin Foretrex models, weighing around 3 oz, can preload a distant UTM waypoint and later point the direction to it as effectively as the heavier Etrex models. Nothing fancy, just the basic function that these tools are supposedly good for.

BTW, for anyone who has ever lost a compass and is looking for a cheap but usable one to carry for back up, picked up a Coghlan's model# 8160 for $5. It has adjustable declination and degree markings, with negligible weight in a small disc-shaped plastic housing with closing cover.

BTW#2. Try using a compass at Red Dirt Pass in the Zirkel CO wilderness. Useless. Explains why the dirt is red.

Samuel, the Garmin Foretrex units tend to be very small with a very small display, and mature eyesight may be a problem. Personally, I think you would be more happy with a larger unit with a larger display. On the other hand, I got tired of carrying around the larger units with larger displays, and just a few months ago I purchased a Garmin Geko, mostly just for the 3-oz weight like you were thinking. It's OK, but you don't get something for nothing.

I was on a group backpack trip in Kings Canyon National Park several years ago, and I had my Garmin GPS12XL. We would go on trails for two days, then off-trail through a 3-D maze for one day, and then back down on-trail for one day. I knew where the off-trail route was supposed to be, and I knew where we were supposed to hit the trail again at one pass. As I looked at my map at home, I noticed a benchmark elevation at that pass/intersection, so I stored that lat/long data to my Garmin. When we got out in the field and were finding our way through the 3-D maze, we were not lost, but I turned on the Garmin and had it point me to that theoretical pass/intersection. We kept going, and as I neared the trail from two miles away, I quit looking ahead. Instead, I just followed the Garmin pointer with my head down. The distance to the point kept diminishing until it hit 0.00 miles. Then I stopped and looked up. I was standing on the desired trail, and the metal benchmark was seven feet directly in front of me. I doubt that hikers need to do any better than that.

Personally, I find lots of map database errors and offsets in the electronic maps inside GPS receivers, and I don't trust them perfectly.

–B.G.–

Bob:

Now that we have an expert here…I have a GPS problem. I noticed a strange symptom on my Garmin 60CSx recently (last time I played with it a month or so ago) — it seems to function properly but the position arrow (I sense we are going to enter into another terminology debate!) doesn't point in the direction of travel. I was next to the Mammoth airport and locked in to some extent by mountains. (I do need to check for firmware updates.) I have NOT troubleshooted yet? I know…RTFM..right? I have used this unit a fair bit in a variety of settings. This is the first time I've had a problem with it.

GPS units work just fine in clouds, rain (don't coat the unit in water!) and snow. Furthermore they work through many fabrics (those with metallic materials can create problems). I often carry mine in the top compartment of my backpack. I generally let the antenna stick out through a tiny space in the zipper — superstition. (I have the unit affixed to a clip in the pack.)

***Clouds, fog, rain and snow are precisely where GPS receivers are most useful! One of the best reasons to get one!***

The units DO fail from time to time for various reasons and they run out of batteries! Duh! GPS technology is well established and well understood!!!

As for old units, about 10 years, after getting my self into a predicament in the Swiss Alps (on a thru-hike of the Alpine High Route across Switzerland), my Dad bought me a GPS. I never figured it out, never used it.

Maybe, three years ago I got the Garmin 60CSx. I use MacGPSPro. Yes, I have had several contacts with Customer Support (the owner answers your email in person!) and if you are a novice, it takes some time to understand but transfer of data points, maps, routes to my GPS is seamless.

Hmmm. I haven't thought about this much, but it sounds like what you suggest, the dreaded RTFM problem.

1. There is no _position_ arrow! There is a display with an arrow that shows you which way you should steer to get to your target destination. Some users have forgotten that they even had a destination entered in, so they don't stop to think about what the arrow is pointing them toward.

2. It does not sound like a firmware problem or a malfunction. I really think that you need to study the user manual a bit, and that ought to clear it up.

3. I've stated this before many times, and I need to state it again. A normal GPS receiver has no idea which way you are facing, or which way it is pointed. As soon as you start to move, then it can see where it was a second ago, and then where it is now, and then it can _calculate_ and assume which direction it is moving. Then, based on the desired destination, it figures out whether you need to steer right or steer left. As soon as you stop moving, it goes back into the slightly confusing state where it doesn't know where it is facing. It does know where it _is_. There are some models that have a compass built in, and they are different.

–B.G.–