Saturday 8 December 2007

Compass or GPS ?

I got this note from Larry Shortt the other day. Larry is one of the fellows who along with Walter Regan and other volunteers works hard at The Sackville Rivers Association, a non-profit organization dedicated to the restoration and preservation of the Sackville River Watershed :


"Hi Guys,
If any of you are into Topo Maps this is a great program for your pc. I have the Maritimes version that I bought about 5 years ago for $100.00 which has the topo maps of NS, NB, PEI and the Gros Morin area of NL on it..

If you go to:
http://www.softmaptech.com/en/volumes/volEN_Maritimes_topo50.html

Handy for finding secret fishing spots..

Larry"


That got me thinking about: Compass or GPS?

When I was younger I once got lost in the woods. I didn’t do anything particularly stupid to find myself in the situation, ordinary stupidity is usually sufficient for that sort of thing but nonetheless; there I was.

Ever since then I’ve followed some simple rules whenever travelling in the back country.

First, I always look at a map of the area to gain some familiarization with the lay of the land.
 Topographic maps used to be my preferred choice but now I use Google Maps or Google Earth as often as not.

I always have a compass and two fire sources with me. I keep the fire sources each in different pockets. Usually I have a disposable lighter in one pocket of my fishing vest and some waterproofed matches in another piece of clothing, my pants pocket or jacket.

I also have a good pocketknife with a lanyard that I carry with me. With that basic kit I have no problem lighting out with just a compass bearing and the promise of good fishing at the far end of a long walk. Recently though I’ve been thinking about getting a GPS unit.

For interest’s sake here is how a GPS works: The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense.

 Some time in the 1980’s these were made available for civilian use.

The GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is.

A GPS receiver must have a clear lock on at least three of the 24 satellites to plot its longitude and latitude position. With 4 satellites locked, it can also plot altitude. Having that data, the GPS unit can then calculate and extrapolate other information such as speed of travel, bearing, and distance to destination, sunrise or sunset time and more.

The way a compass works is like this.

Picture the earth’s magnetic field, its like a giant bar-magnet run through the centre of the globe. This bar has a north end and a south end. A compass is just a magnetized needle balanced on a pin that allows the needle to move freely.

With magnets the rule is, "opposites attract" so the south end of the needle swings to point toward the North Pole. This end of the needle is usually coloured and marked with an “N”.

It’s almost impossible for a compass to be wrong. It can be a little bit out because of a thing called declination – the slow movement of true magnetic north - but for just taking a bearing to get you through the brush and back it’s hard to beat.

A GPS on the other hand can memorize way points such as where you left your car or where the honey-hole is on the featureless surface of a lake.

Have you ever emerged from the bush onto the road where you’ve left your car and not been sure whether you should walk left or right to get to it? Never happens with a GPS if you’ve set your vehicle as a way point. So the advantages of the GPS are pretty obvious.

What are the negatives? I don’t have a GPS yet so I’m speculating here but I think the size of the unit is a pretty important consideration. Weight aside, the harder it is to stow, access and re-stow, the more likely one is to lose it, drop it or leave it home altogether.

The basic ruggedness of the unit is pretty important. I don’t know about you but when hiking through the bush I’m always banging off trees, slipping on logs and generally beating my gear and myself up pretty badly.

That’s when I’m not falling into the water I’m trying to fish.

Then there is the question of batteries. I guess you need to carry a spare set of fresh ones as well as put new ones in the unit before a day afield. I also wonder about how clear the canopy above has to be to get a good reading. That is a lot of stuff to think about before even looking at prices.

 I paid about $15 bucks for the compass that over the last twenty years has gotten me into and back out of more adventures than I’d dare to tell. It fits comfortably in my pocket with no weight, no fuss and no batteries. Wet or dry it works without fail.


I’d really like to hear from anyone who has had experience with these GPS things. I’m almost convinced that I should get one but I suspect I’ll still carry my old compass anyway. It just gives me a sense of security.

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15 Comments:

Blogger Andrew Crawford said...

I used to wander around the Renfrew Heights armed with not much more than a pair of really thick Barbour thornproofs and one of the early Garmin handheld GPS devices.

It certainly makes ground navigation a lot easier, particularly in areas where you really can't be certain which distant mist-covered hill is the particular one you're trying to get a fix on.

They're a great aid to safety too - if you do fall through the vegetation to the bottom of a crevass fifteen feet down, breaking a leg, and facing the certainty of a a slow and agonising death without any possiblity of rescue, at least you'll have the comfort of knowing exactly where it is that you won't be rescued from.

The only real problems I had with it was the fact that it ate batteries at an astonishing rate - I'd go through sixteen AAs a day - two changes, and that it was completely unable to get a fix if there was so much as a wet leaf in the sky above it. Being Scotland, if there was a leaf, it's sadly a pretty safe assumption that it would be wet.

8 December 2007 at 20:16  
Blogger Steve Dobson said...

Well, Andrew;
The battery thing has me a bit put-off. Can there be anything more useless than an electric compass with dead batteries? I'm not sure what happens when they are dead. Is there a built in magnetic compass or are you just up the creek?
Thanks for adding the map link to your comment.

8 December 2007 at 20:46  
Anonymous Anonymous said...

I agree, there should be at least a simple compass built into a GPS in case the batteries die or the electronics get fried.

9 December 2007 at 00:46  
Blogger Steve Dobson said...

I wonder what the battery life is like on a new GPS. Any ideas?

Cheers,

9 December 2007 at 01:13  
Blogger Andrew Crawford said...

I understand that the battery life is much improved - most of the newer ones have rechargable Lithium Ion battery packs with much higher capacity than the AAs I was using. Also there are low-power specialised processors available to do the GPS maths.

9 December 2007 at 08:19  
Blogger Steve Dobson said...

You know Andrew,
I've been thinking about the battery issue and there are little hand-crank generators that power flashlights and radios with an available power tap for cell-phone charging. There is also a solar cell mat that goes on top of your back-pack for charging phones or digital cameras. If the GPS doesn't have a jack point for a device like that, it would probably be fairly simple to hook-up. I'll look around the web for some schematics and see if it makes any sense.
Cheers,
Steve

9 December 2007 at 18:22  
Blogger Random Phrump said...

Steve: I know someone who is an expert on GPS - Daryl Hayes. He is a retired educator - former VP at Teacher's College in Truro. I met him at the NS Agricultural College in Bible Hill in October at the NS Technology Educators' Association Conference, where I attended his workshop on GPS.

Daryl works with the Eastern Shore Ground Search and Rescue, and has extensive experience with GPS devices and with computer software that interfaces with them. I'll send him a message that directs him to this discussion. Maybe, he will respond.

9 December 2007 at 19:02  
Blogger Steve Dobson said...

That would be great Warren,

It would be good to hear from him. I'll keep my ears open for any GPS workshops coming up as well.

Cheers,
Steve

9 December 2007 at 22:33  
Blogger Steve Dobson said...

By the way,

If you follow the map link in the first comment from Andrew, zoom in all the way at Heathfield. There are some interesting ruins there. If you are still following this discussion Andrew, maybe you could tell us what they are.

Cheers,
Steve

9 December 2007 at 22:42  
Blogger Andrew Crawford said...

If you're looking at this place, it's an old farmstead. Heathfield was a hamlet inside the Muirshiel Estate but it's long been uninhabited. According to the RCAHMS Canmore database[1] the site was included in the first Ordnance Survey map of the area in 1863. There's a picture of the actual place here on flickr.

Those ruins are very well known because the road that goes by there is the main (and only official) access to Muirshiel Country Park, which was once a huge baronial estate that was left to the Scottish nation. It's absolutely huge, and of particular interest to rock hounds, includes an abandoned baryte mine further along the road in question.

The terrain varies from forrested and pastoral in the valleys to windswept and exposed hills where only moss and thin grass can survive. The soils are thin and the glaciated olivine basalt bedrock is frequently exposed. Despite the harshness of much of the terrain the whole area has been extensively settled since the Iron age - and the ancient Celts, the Romans, medieval stonemasons and eccentric 19th century landowners have all left their mark.

I tried to find some links to pictures which show the area. The problem is that the scenery is so extreme that it doesn't look quite real in a photograph - like this one where the slope behind the sheep is actually 800 feet high. Have a look at this one or this one or this one.

This is the countryside I grew up with - I was raised in Kilmacolm on the North edge of this huge muir.

[1] Being a Government site, you can't do anything useful like link to the actual database entry... if you click on "Canmore" at the bottom then "mapping search" you can find it yourself though.

10 December 2007 at 00:01  
Blogger Steve Dobson said...

That's the place, thanks Andrew;

The photos are amazing. I really expected to see a castle or something a la Brave Heart. The terrain as you say is unreal. Here is a question for the group, I always wondered why there wasn't more stone building like this in Newfoundland?
Thanks again for the links.

Cheers,
Steve

10 December 2007 at 00:30  
Anonymous Anonymous said...

Steve

Great blog. I have enjoyed reading your posts. I have learned some stuff from you so will gladly help you out with some GPS info.

I use a Garmin eTrex Legend which is the cheapest handheld unit you can buy with a base map. I wouldn't buy one with out a base map and here's why. If you happen to get lost and you forgot to mark your car or any other known point and don't have a topo map on hand then it doesn't help you much. With the base map you can see roads, etc and normally figure out where you parked and mark it on the map. Also if you do have your starting point the GPS will send in a straight line while there may be a road or powerline close by that would make the walking easier.

I have the Garmin mapsource topo maps on my unit and can see all rivers, ponds, brooks, roads and even some trails. The detail is so good that you can even spot possible pools on alot of brooks and rivers.

I use rechargeable batteries and on a full charge they run the unit easily all day. About 18 hours or so if you leave it on. I keep a couple of fresh alkalines in my waist pack but have hardly ever had to use them. The ones with color screens are harder on batteries. Probably get 12 hours on those.

The Legend is the cheapest model so it has the worst antenna and often loses its position lock in heavily wooded areas and especially in river and stream valleys. If I was buying another one I would buy the newer eTrex Legend HCx which has a color screen (much easier to distinguish roads from waterways), a card slot for storing alot more maps, and a high sensitivity antenna which I have read is much better at holding the GPS signal in tree cover. It is about $270-$280 versus the $160-$180 for the regular Legend. Easily worth the extra money in my opinion.

These units come with a basemap but it is not very good because it covers North America with limited storage space. You can buy road maps for Canada for about $100 and topo maps for Canada for $130. Then you download the ones from your region onto the unit. You can download these maps from pirated sources on the web but you take your chances. Or alternatively you can borrow the CD's from someone who has them and load them onto your computer.

Another question I saw you ask was about the compass. The next unit up from the Legend has an electronic compasses built in but the Legend only has a bearing dial that shows you what direction you are moving. It doesn't work standing still. I don't know if I would pay the extra $40 for that because it still wouldn't work without batteries.

Anyway I hope I have helped you out a bit. I can give you more info if you want. Feel free to ask. If you do I will send you an email and you can send me a message directly.

Geoff Jamieson

10 December 2007 at 06:42  
Blogger Steve Dobson said...

Hey Geoff,

Thanks for the information. I did a search for the models you recommend and the local Best Buy has the HCx and a cheaper model (about -$50.00). I'll go in and check them out after the holidays.
The manufacturer's web site says they get about 25 hours from a set of alkalines. I'd be happy with eighteen which sounds more realistic. Your comments on the base map make sense too. Much better to walk a power line than bushwhack through some of the country we fish around here. I didn't even think about loading local topo maps into the unit but what a bonus. I wonder how often I've turned back a kilometre before a brook opened up into a dream pool. I know I've followed a brook a kilometre farther than I should have more than a few times.
Bearing in mind, pardon the pun, that I've never used a GPS. The compass question probably becomes moot with experience. My compass is attached by a lanyard to my wader suspenders so it'll be along for the trip anyway, at least the first few times.

I don't know enough yet about how much I don't know but I'll take you up on your offer of more info when the time comes. Thanks again for such a comprehensive post. I hope to hear from you again.

Cheers,

Steve

11 December 2007 at 04:25  
Blogger Random Phrump said...

Hi Steve:

My wife wants to get me a present - I told her a GPS receiver would be nice. Then I asked Daryl Hayes via email what his recommendation would be. He replied.

"The GPS you should buy is the Garmin 60Csx which will have the barometric altimeter and electronic compass. You should be able to buy this one for between $300 to $350 CDN There is a $50 mail in rebate on this model if purchased before the end of December 2007. You then have until the end of January to Apply for the rebate. The 60Csx is the best hand held available at this time."
Daryl

18 December 2007 at 00:04  
Blogger Steve Dobson said...

I appreciate Daryl's input. Thanks.

Even though the the 60Csx is a model up from the one Geoff is talking about, the mail-in rebate puts them pretty well in the same price range.

Cheers,
Steve

18 December 2007 at 04:16  

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