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Is GPS All in Our Heads?
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eric chan
(bearbreeder) - F
Is GPS All in Our Heads? on 02/05/2012 22:38:29 MST Print View

more at link ...

IT’S a question that probably every driver with a Garmin navigation device on her dashboard has asked herself at least once: What did we ever do before GPS? How did people find their way around, especially in places they’d never been before?

Like most questions asked in our tech-dependent era, these underestimate the power of the human mind. It is surprisingly good at developing “mental maps” of an area, a skill new research shows can grow stronger with use. The question is, with disuse — say, by relying on a GPS device — can we lose the skill, too?


If maps help us, what is the problem with GPS? A lot: in my opinion, it is likely that the more we rely on technology to find our way, the less we build up our cognitive maps. Unlike a city map, a GPS device normally provides bare-bones route information, without the spatial context of the whole area. We see the way from A to Z, but we don’t see the landmarks along the way. Developing a cognitive map from this reduced information is a bit like trying to get an entire musical piece from a few notes.

a b
GPS on the brain on 02/05/2012 23:13:25 MST Print View

This brings to mind something funny that happens at my work.
Most of our guys are in their 20's and have never used a Thomas guide map book before.
They rely on the company GPS units or their Android phones.
If those electronic devices don't recognize the adress my co-workers freak out.
I mean they won't even begin driving towards the general direction of the city the job is in until they get the electronic box's (GPS) permission.
They think I am some far out old man when I pull out the Thomas map guide and thumb through the index.
Interestingly, even when i show them the job location on the paper map they still wait until they get the GPS unit to issue step by step directions.
Or they call the customer to get a cross street and then enter that into the GPS.
My favorite GPS "wild goose chase" occurs when the Android phone they are using begins hunting between wireless networks.
Suddenly the job is behind us.. nope now it's ahead of us.. nope IT MOVED AGAIN!
Or the day the GPS kept sending us left, and left, and left again until we came full circle.
It is tough being a cranky old map and compass guy around the GPS generation.
It is also pretty dang hilarious!

Tipi Walter
(TipiWalter) - F
Dump GPS on 02/06/2012 06:49:38 MST Print View

Dump the gps doodad and take a map. And once you know the area, well, you can even dump the map. I love to see guys tabulating numbers on the trail and consulting their handhelds and drooling over waypoints and all other such nonsense. While you're at it, deep six the SPOTS and PLB's and all the rest.

And please, don't write up a trail guide to an area and include GPS numbers. It's a totally useless endeavor. Write about water sources or a seven day blizzard or pole bending mountaintop winds or even Notes on How To Birth A Mountain Turtlehead, but please leave the gizmos behind. Do us all a favor.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: Is GPS All in Our Heads? on 02/06/2012 07:13:58 MST Print View

The spacial context problem should mostly go away as the pixel density of screens increase. The small screens are already incapable of displaying the amount of information in the same area shown on a paper map. Big screens are even worse since they don't show anything more, but are much bigger.

Buck Nelson
(Colter) - MLife

Locale: Alaska
What's best is both the navigational skills and the GPS on 02/06/2012 07:43:30 MST Print View

I consider myself fairly proficient with a map and compass. That said, the GPS is an awesome tool and there's a reason that they are so popular.

To me, the ideal balance is to have a GPS when navigation is challenging, but having the skills to fall back on map and compass in the event of GPS failure.

Sarah Kirkconnell
(sarbar) - F

Locale: In the shadow of Mt. Rainier
Re: What's best is both the navigational skills and the GPS on 02/06/2012 08:17:16 MST Print View

Bruce has it right - there is nothing "evil" about GPS if it used as a tool. Sure, I can read maps and whatnot but I enjoy a GPS as well. Oddly enough I use my GPS more for figuring out mileage when hiking than for direction.
I have an integrated GPS in my newest vehicle, if I am driving my husband's truck we have a car unit or we can use our phones if we want. If I have somewhere to go I map it online first and then knowing the route, I go use my GPS in the van.

I don't exactly miss using a massive paper map/book of maps when driving.....

Erik Basil

Locale: Atzlan
Thomas Guide? Wut? on 02/06/2012 09:54:14 MST Print View

I love that we haven't had to update/purchase a new Thomas Guide in several years, because the data in our Nav units is accurate. I also love that some of you folks apparently still have them and I will admit there's one behind the seat in our Jeep.

However, having a 6x9 inch screen in my dash that gives me map data is just outstanding. Even the little Garmin is pretty darn good. It has "favorites" that include every In-n-Out Burger joint, and every "Triple D" restaurant.

In my case, this only goes to automobile nav. Our Garmin GPS unit is out of order and I like maps.

Edited by EBasil on 02/06/2012 09:55:55 MST.

ed hyatt
(edhyatt) - MLife

Locale: The North
GPS on 02/06/2012 10:09:35 MST Print View

I'm in the 'like GPS a lot' camp; and use it for 99% of my 'using things other than my senses' navigation.

My GPS is a simple Garmin with an arrow. I'll use it a few times a day perhaps to get a rough idea of direction (or in foul conditions, location). The rest of the time I rely on 'natural navigation' - using my eyes and experience to gauge the topography and project where 'the route' should be.

My map and compass stay on my pack. GPS is faster for on the fly nav for me.

Sarah Kirkconnell
(sarbar) - F

Locale: In the shadow of Mt. Rainier
Re: Thomas Guide? Wut? on 02/06/2012 11:35:54 MST Print View

Hehheh...mine in the van is set to recognize any Starbucks that I might be near. And as well ANY latte hut :-D Yum!!

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Dump GPS on 02/06/2012 12:18:52 MST Print View

The article was more about road travel. But I agree with Walter.

Seems to me, if you are backpacking and carrying a map as a backup, you might as well leave the GPS at home. This is BPL, which emphasizes multi-use, not redundant systems.

However... Maps and compasses are technology, same as GPS. So there is nothing wrong with using technology. I think the article is more about how we are becoming so specialized in our lives, we are loosing the ability to function independent of the technology.

Now regarding traveling on roads and in cities. I travel a lot to distant cities and need to drive many places once I arrive. I map my routes ahead of time using MapQuest. This gives me a good feel for where I am going, they lay of the land, and road systems. I study them ahead of time. Sometimes I bring a Garmin with me, because it is not safe to be reading a map when driving. But I know where I am going ahead of time.

Even when driving in So Cal in unfamiliar areas to a trail-head, meeting or event I print out the MapQuest maps first even though I have a navigation system in my vehicle. Sometimes the Nav system routes a goofy and longer route, which I catch right away because I know where I need to go from a high level perspective.

Now when in a city and on the spur of the moment I want to stop somewhere unplanned, the iPhone is great to grab the address and I punch it into the Nav. Much better to listen to the lady in the dash giving turn-by-turn directions than trying to look at a GPS screen. And I always carry state maps in the vehicle.

David Roach
(DRoach) - F

Locale: North America
Driving vs Hiking on 02/06/2012 15:57:39 MST Print View

When I'm driving I love my Droid for it's GPS. It's a tool. Sometimes it doesn't work. 99% of the time it does. But, if I'm out hiking? Map and compass all the way. The electronics can stay in the car or at home.


Sarah Kirkconnell
(sarbar) - F

Locale: In the shadow of Mt. Rainier
Re: Driving vs Hiking on 02/06/2012 19:06:25 MST Print View

Ugh. Please, please for the love of whatever do NOT leave electronic toys in your car at the trailhead (GPS, phones, etc). It only encourages criminals to bust into cars!!!!!

Look, if one is against GPS they shouldn't be carrying a phone, a camera or even a watch then, eh? Or worse, a lousy altimeter!

ed hyatt
(edhyatt) - MLife

Locale: The North
GPS on 02/07/2012 00:09:41 MST Print View

It is BPL...but I don't see what else can replace something that tells you where you are to 5m in a Scottish blizzard or the mists that cloak this fair land all too frequently.

I guess in SoCal you can always discern the nearest Starbucks through the heat haze so nav is never an issue :-)

Piper S.
(sbhikes) - F

Locale: Santa Barbara (Name: Diane)
Re: GPS on 02/07/2012 19:53:02 MST Print View

The GPS in the car is fun to use when you don't know all the freeways to take to get somewhere. But I don't know how to use a hiking GPS. A lot of the time, I have to find my way by looking for signs of trail that look like this.
hidden trail
In other words, to find the trail means looking for areas where the weeds are a different color or a different species. There are many ways to find your way.

Harald Hope

Locale: East Bay
gps + sustainable earth frienddly? I don't think so on 02/09/2012 09:52:11 MST Print View

gps systems require a global satellite system to function, used to use the military one but I believe they are putting up civilian stuff now due to the popularity, ie, many more rocket launches. There is nothing earth friendly about satellites, the launches are incredibly toxic, the orbits decay, and require replacing the systems at routine and in terms of human history, almost absurdly short intervals, every step of the process just takes us further away from nature, which to me is the precise opposite of why I go backpacking. Sort of the same idea as not being able to listen to the sounds of nature and needing further stimulation via music player of some type.

However, convenience always trumps any larger considerations in today's consumer society, so there's not much point debating the matter from what I can see. John Muir must be rolling over in his grave nowadays, I feel for his spirit. Backpackers used to care, some deeply, about such questions, but I guess those times are fading now, very sad.

A compass is a piece of metal that points to our north pole, period, with some fancy refinements if you want.

An altimeter is a similarly simple device. Comparing the complexity levels of these different methods is a no brainer, a compass is a simple device, requires almost no support infrastructure to produce, but requires some skill to use well.

I'm not so addicted to cell phone usage that I consider it a necessary item, it sits sort of half way between a basic compass and a gps in terms of the infrastructure required for it to be more useful than a fancy small paperweight, but, like the GPS, is totally and utterly non-sustainable, the peak of human throw-away culture and wastefulness. Happily, looking long term, all such non-sustainable systems must, by definition, be unsustainable, and will fade away, leaving behind a damaged earth and ecosystem, but also leaving simpler tools, not requiring globally complex systems to maintain, that have withstood the test of time, like a compass.

Edited by hhope on 02/09/2012 10:01:26 MST.

Diplomatic Mike

Locale: Under a bush in Scotland
Compass on 02/09/2012 10:01:56 MST Print View

"A compass is a piece of metal that points to our north pole, period, with some fancy refinements if you want."
It actually points to the magnetic pole. ;)

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: gps + sustainable earth frienddly? I don't think so on 02/09/2012 10:49:36 MST Print View


I agree whole heartily.

I try to separate myself from the technology when hiking. No GPS, no cell phone, no MP3, and often no camera. But I do use a light, a compass, topo maps, synthetic fabrics, plastics, metals, etc. So we cannot get away from it. Also our technology driven society is more and more making people very specialized in itty bitty fields. So it is natural for people to gravitate to the technology. Plus many do not have the free time to go out often or for long periods of time, and the technology becomes more and more a reliance piece of the adventure. I don't think that is a good thing, and others think it is wonderful. And we are both right.

I posted in another thread about Shamans who traveled from northern Utah to the edge of the eastern Sierras for religious purposes. Today it would be the rare person who could undertake that kind of trip with no reliance on technology or society.

The most important thing is for people to go out and be safe, and for many a GPS is the only way they can do it. Others use a hybrid kit, and others only map and compass. On most of my trips I don't even need a compass, a map is sufficient... and that is technology too. So although I have been vocal about my distaste for GPS, I am not right; there is no right. And I have used GPS a little bit, it does have its place in backpacking. I guess it all comes down to HYOH. We all get a bit "religious" about what we think is best, I am one of the worst offenders, but in the end it doesn't matter. What works for each person is the best way to go. We cannot get rid of technology, technology is both good and bad. Much is not sustainable, but mother earth will eventually take everything back. Species come and go, and only mother earth goes on.

Thomas Glennon
(Eagletrek007) - MLife
It's All Good on 02/09/2012 11:12:43 MST Print View

While I'm new to the community, I'm fairly well versed and practiced in land navigation. The OP is quite correct about folks becoming so focused on their GPSr that they loose focus of their surroundings but that doesn't mean that GPS is a bad thing. It's like anything we own; it's all about how we use it.

When out and about, I carry a map, compass and GPSr. Of the three, the map is most referenced, the compass ocassionally and the GPSr is there to be used when required. Terrain association is my primary navigation skill and the compass is only needed when I can't determine a cardinal direction via other means or when I want to determine a location through resection or intersection. The GPSr is there only to bail me out when everything else goes to hell (especially the weather) and I need a quick fix on my location.

There's nothing wrong with blending the old and new. OBTW, I know this is BPL and I noticed previous posts that reminded me of that. That said, what is the lbs/oz thresshold that has to be crossed before I enter the realm of BPM??? :0)

Trek On

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: gps + sustainable earth frienddly? I don't think so on 02/09/2012 15:04:05 MST Print View

" gps systems require a global satellite system to function, used to use the military one but I believe they are putting up civilian stuff now due to the popularity, ie, many more rocket launches. "


Navstar satellites are designed for the military and funded by DoD.


drowning in spam
(leaftye) - F

Locale: SoCal
Re: Re: gps + sustainable earth frienddly? I don't think so on 02/09/2012 15:45:21 MST Print View

Isn't the european gps system commercial/civilian?

Edit: I looked it up. It's also a government system.

Edited by leaftye on 02/09/2012 15:49:19 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: gps + sustainable earth frienddly? I don't think so on 02/09/2012 16:17:33 MST Print View

Global Positioning System is a U.S.-funded system.

Europe has Galileo, which is government funded as well.

GPS is not Galileo.

Each of these systems have different services supported. Some services are military in nature, and some are purely commercial. Some services are classified.


Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: gps + sustainable earth frienddly? I don't think so on 06/20/2013 18:59:07 MDT Print View

"It's also a government system."

Galileo is still a _future_ government system that resembles a money sink.


Greg Mihalik
(greg23) - M

Locale: Colorado
The Lazareth GPS thread on 06/20/2013 19:05:24 MDT Print View


Did the real Bob Gross resurrect a thread that is 16 months old?

That's pretty desperate, even for Bob.

(You never know who in that cadre is really posting....)

Edited by greg23 on 06/20/2013 19:22:51 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: The Lazareth GPS thread on 06/20/2013 20:13:19 MDT Print View

I had been traveling for three weeks. When I got home, there was a telephone message from a complete stranger asking questions about GPS, and he had gotten my name here at BPL. What I did not understand was how he got my home telephone number. So, I thought that I would post something innocuous here on the GPS topic, and maybe he will pop up again.

Mostly it is just federal employees who call in the middle of the night asking GPS questions.


jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: The Lazareth GPS thread on 06/20/2013 20:44:43 MDT Print View

The NSA has your telephone number

And a record of all your calls

David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Re: The Lazarus GPS thread on 06/20/2013 20:50:40 MDT Print View

>Did the real Bob Gross resurrect a thread that is 16 months old?

The real Bob Gross can post about GPS whenever he wants.

Just like "Chuck Norris does not sleep. He waits.", the real Bob Gross doesn't need an antenna, he IS an antenna.

Brian Lewis
(brianle) - F

Locale: Pacific NW
GPS as nav learning tool on 06/20/2013 21:01:08 MDT Print View

Back to the original topic ...

I don't think anyone has yet mentioned that a GPS can be useful for at least some people as an *aid* to learning land navigation. For one thing, it can be pretty helpful to determine and/or confirm that you're at a particular spot, just to give solid feedback on what you're doing. A mapping GPS can help a person learn the relationship between a map image and what's on the ground.

While I agree with the concern that we can rely too much on GPS and lose (or never gain in the first place) solid map skills, I think it's worth pointing out how helpful the device can be in establishing those skills too.

It's somewhat reminiscent of the debate some years ago about how the spread of electronic calculators would result in future generations of kids who can't do basic math. While I'm not certain, it appears to me that particular issue is being resolved by nearly universal availability of calculating power, and indeed less or no pervasive skill at things like long division.

In the same way, the GPS is clearly here to stay; we should push for folks to learn solid map reading skills above and beyond "how to use a GPS app", but don't pretend or hope that GPS isn't a tool that they'll use, and leverage the device for what it's good for as a teaching tool.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: The Lazareth GPS thread on 06/20/2013 21:01:15 MDT Print View

"The NSA has your telephone number"

Actually, it is an NSA guy who used to call me in the middle of the night asking some GPS question.

I knew that he worked for NSA, but he would never verbally reveal that he worked there.


David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Old and new on 06/21/2013 00:30:20 MDT Print View


I'll readily agree that GPS is here to stay and, like magnetic compasses, sharp edges, and clothing; we're not going back.

Here's a last-generation example of the useful of a "non-essential" technology. In my first decade of backpacking, there were times when I'd be sure that the campsite was just over the next rise. And then just over the NEXT rise. And AGAIN, over the NEXT one. It was exhausting. Having a Thommen altimeter solved all of that. If the campsite was at 9,400', I knew exactly how much hiking I had to do up that slope and I paced yourself accordingly. Did I "need" that technology? No, not on most days. But the added 2 ounces made, on balance, for a more pleasurable trip.

Did I sometimes *need* that technology? Yea, maybe. In a white out, on Pyramid Peak in Desolation Wilderness in Winter, it increased our safety A LOT to know exactly when to cut over to the next drainage while avoiding the steepest terrain.

That said, I'll pit my 13-year-old son (without paper or pencil) against you any day in multiplication, division, algebra, trig, calculus, or number theory; you with or without your slide rule. Just because we don't HAVE to have older skills, doesn't mean we can't and there are sometimes advantages to doing so.

Pete Staehling
(staehpj1) - F
Just another tool on 06/21/2013 08:41:48 MDT Print View

GPS is just another tool. I figure that it is worth taking and using when the smart phone is going any way or when it is lighter than the maps and guide books it replaces.

If you are somewhere that you should have back up navigation system you probably should a backup with paper maps and a compass too. Maps can be lost or blow away. I think we are very close to the point where the GPS can be as reliable as a paper map.

Personally I have usually left the handheld GPS at home and used paper maps on most trips, but as I become more comfortable with the functionality and reliability of my smart phone I am more and more likely to use it. That comfort has been growing as I have been logging my daily trail runs with MapMyRun on my android phone

I plan to use the smartphone on my next longish trip (JMT). I am still debating how much paper to take.

spelt with a t
(spelt) - F

Locale: SW/C PA
Re: Just another tool on 06/21/2013 09:28:06 MDT Print View

I wouldn't feel comfortable with a GPS if I didn't have map and compass skills. I don't care one way or the other how people rationalize their choices, but personally once I learned, maps became a lot more fun. That alone makes investing in a GPS unit unappealing.

David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Multipurposing on 06/21/2013 10:02:54 MDT Print View

> I plan to use the smartphone on my next longish trip (JMT). I am still debating how much paper to take.

Pete: Clearly (GPS or not), someone needs to print the JMT, PCT, and AT maps on toilet paper at a scale of 1 sheet per mile. 20 miles per day = 20 sheets per day. There could be larger and smaller scales for faster and slower hikers.

> I wouldn't feel comfortable with a GPS if I didn't have map and compass skills.

I feel that way about electronic calculators. If you can't use a slide rule, you have no business in science or engineering. I mean, what if a EMP comes through and fries all circuits? Now removing tongue from cheek.

Rob E

Locale: Canada
Navigation is a skill not a tool on 06/21/2013 10:27:05 MDT Print View

A compass can be lost or damaged. The declination can be set incorrectly, or even inadvertently changed while being used*. A piece of sand/grit/dirt can get stuck in the bezel and the compass might no longer rotate properly*. You can be standing over a highly magnetically susceptible rock unit which will change the magnetic field and thus change the reading of the compass*.

* all have happened to me during my career as a geoscientist.

A paper map can be lost or damaged. It can also be incorrect or not updated to reflect recent changes. A hiker who finishes with a map section might follow ultralight doctrine and burn that map section at night, only to find some obstacle/injury/disaster has forced them to backtrack and now they no longer have a map. A map can be ignored: the so called 'bending the map' phenomenon when people get lost. A map might not have the necessary features to be safe: the resolution of the topographic lines might not be fine enough to indicate the upcoming dangerous rapids in a river, or to indicate the presence of an impassible vertical cliff.

An altimeter can be lost or damaged. The batteries can run out. It can be incorrectly calibrated. The user might inadvertently get the units confused and read the display incorrectly (mBars vs inHg vs feet. vs meters). Weather systems can come in and change your altitude drastically even though you haven't moved. The altimeter might not be enough information to uniquely determine your position or to provide adequate route information, "we know we're somewhere on this contour line... but not sure where along it".

A GPS can be lost or damaged. The batteries can run out. It can be set to the wrong map datum/geoid. It might not work well in some terrains. A critical waypoint might be incorrectly entered by the user. The GPS satellite constellation may be damaged or disabled.

A smart phone can be lost or damaged. The batteries can run out. Without network coverage the user might have not downloaded the maps they thought they had, so now they only have their lat/lon, but no maps. The smart phone might only give coordinates in lat/lon, but you have a paper map with only a UTM grid (or vice versa).

Your Loran-C/VLF radio beacon navigation device can be lost or damaged. There might be a magnetic storm that prevents it from operating correctly. The network of radio beacons could be disabled. The government pulls the plug on the Loran network (or have they already?).

A sextant can be lost or damaged. Your chronometer might not be set correctly. You might misread the verner scale. The stars/sun/moon might not be visible. You lose or misplace your almanacs/tables. You might have no idea how to use a sextant.

Folksly wood-lore might be forgotten or misapplied. The moss might grow on both sides of a tree. You are in a valley and couldn’t discern the direction that the sun had set. You are in overcast skies with completely flat light, there are no shadows, and you cannot determine the direction of the sun or moon. You are at a hydrological divide, so aren’t sure if a river system drains to the Hudson Bay, or the Mississippi.

Navigation is a skill, not a tool. The whole debate of one which navigational tool/aid is universally better in absolutely every scenario than another is just like any other heated BPL debate: windshirts, rain paints, down vs. synthetic insulation, TP vs. rocks, knife vs. scissors, sawyer vs. steripen.

Now, I will throw in my two cents and say that I sometimes carry a map and compass, a GPS, both, or neither, depending on the trip.

Call me reckless, but since I once briefly inhaled campfire smoke as a child I’m not long for this Earth anyway.

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Navigation is a skill not a tool on 06/21/2013 14:27:42 MDT Print View

I agree navigation is a skill, but for most people venturing into unfamiliar territory, it's a skill that depends on one tool or another, whether it be a map & compass or electronic gizmo. As any tool can fail, so it's prudent to have a backup system.
But, navigation is a skill and skills needs practice, so you must practice with both you primary and backup tools so you are proficient in both.

I quite proficient with a map & compass, but I have to admit that a GPS can save a lot of time and anxiety in a whiteout.

Mark Regalia
(markr) - MLife

Locale: Santa Cruz
Mixed Feelings about GPS on 06/21/2013 16:34:46 MDT Print View

I hike in the Sierra Nevada. Mostly it is so open and vertically differentiated that you can get along fine with a compass and map. Heck, I seldom use a compass. I don't think I will carry a GPS anymore.

I could see the value of a GPS for bushwhacking, especially in forested or very brushy country. We got lost once in a very brushy section of the Siskiyous going cross country in fog that was so heavy we couldn't see very far ahead. A GPS would have been very nice.

When I was a forester in the Sierra and needed to know exactly where I was so I could map out my plots so that people could find them later I dreamed of something like a GPS. They didn't have them then. My buddies who stayed in the field now use them routinely.

I do think that they are much better than maps in cars when you don't have a a navigator with you. But you have to do your homework before starting. I kind of memorize the map so if the GPS sends me way wrong, which it has, I will hopefully catch on to it and re-navigate. I have also used it when I took a wrong turn. It can find me a way back.

Rob E

Locale: Canada
Re: Mixed Feelings about GPS on 06/21/2013 18:18:25 MDT Print View

" ... so if the GPS sends me way wrong, which it has, I will hopefully catch on to it and re-navigate."

Although "GPS" is named a "positioning system", it really is just an accurate timing system. "Global timing system" would be a more apt name. GPS receivers, through a variety of clever techniques, determine the amount of time it takes for several signals transmitted from low orbiting satellites to propagate to your antenna, to within 10s of nanoseconds. GPSs don't "measure" position, they measure time differences. As a consequence of measuring time differences, position can be calculated*.

Why is this important to the discussion? Because "GPS" only measures propagation time of signals. Everything else is calculated. "GPS" isn't a car icon on a street map with soothing voice instructions to turn and follow a route. That is entirely a computer program. "GPS" isn't a handheld computer with a color display that shows your location plotted on a map with a track and waypoints. That is entirely a little handheld computer and a computer program.

In your example, "GPS" didn't send you the wrong way. A GPS receiver measured timing information of signals from space to within a few 10s of nanoseconds, and from this, it calculated your position accurately while you were travelling at a fairly high velocity. This in itself is a pretty awesome technological feat.

A computer program with a database of street map information, running on a small form factor computer with a little LCD display sent you the wrong way. GPS had nothing to do with it, except provide your location. Your location could have been provided by any number of ways: you could have input it directly, it could have attempted to triangulate your position from the stars, radio beacons, or from wifi networks (as apple ipod touchs do for example).

So, why the rant? This whole thread started with an article that GPS is making us dumber and that we cannot make mental maps, and that future generations are doomed. I just want to get it clear: measuring signals from space accurately within a few nanoseconds isn't a problem. Trusting little handheld computers running crappy software that attempt to read your mind and tell you where to go is the problem. GPS is great.

Saying that GPS sucks because the voice on your Tom Tom sent you the wrong way is like saying that magnetic navigation sucks in 200A.D. because paper maps didn't exist.

* I am not, and do not claim to be, a GPS expert. I am at best, a learned amateur. And am versed in PRN codes, how GPS timing is determined, and have written a couple of computer algorithms to turn pseudoranges into ECEF Earth-Centered-Earth-Fixed coordinates, and then into lat/lon positions, have done some dabbling in ionospheric/tropospheric correction terms, and have manually post-corrected said calculations with updated satellite ephemeris. As I said, not an expert, and I look forward to B.G. et al. correcting me for any discrepancies I may have made.

Edited by eatSleepFish on 06/21/2013 19:57:51 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Mixed Feelings about GPS on 06/21/2013 19:08:45 MDT Print View

Although the term "triangulate" is understood by most, technically a better term would be "trilaterate," even though that is a tough word. A GPS receiver measures tiny increments of time, or the length of sides of various triangles, and it does not measure the angles.

Agreed, the basic principles of a GPS receiver work great. It is only when you start piling on the mapping functions, auto-routing functions, and fancy software that you start getting into trouble.

Once you understand how to measure nanoseconds of time based upon atomic clocks, you will likely quit wearing a normal wristwatch.


David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Nanoseconds. And other units. on 06/21/2013 19:27:22 MDT Print View

A light-nanosecond is a foot. (30 cm in Australia.)

There are 3+pi/4 liters in a gallon.

Water in a pipe or stream travels at 5 feet per second.

An ostrich egg makes an omelet for one dozen people.

Okay, those are all approximations. But very useful ones.

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Nanoseconds. And other units. on 06/22/2013 03:13:21 MDT Print View

"A light-nanosecond is a foot"

In other words, the speed of light is (about) one foot per nanosecond.
Electronic signals travel at much the same speed. So, if you have a 1GHz signal travelling along a wire, the voltage level will change every 15cm. If you look at a PC motherboard, you may notice that many tracks do not take the shortest route. This so that related signals travel the same distance and so arrive in phase.

My favourite unit of time is the nano-fortnight, as in "I'll just be along in a nano-fortnight".