Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Sunday, October 4, 2015

Buying A New Compass

Silva Ranger  - Outdoor Quest Image
There are several things to keep in mind when buying a compass.

My preferred compass is a declination adjustable sighting compass like the trail proven “Silva Ranger.” (Silva, Brunton and Suunto all make good compasses.) The key is that this type of compass can be adjusted for magnetic declination and that keeps your wilderness navigation simple. You can expect to pay roughly $35.00 - $60.00; a cheap compass will not serve the hiker well.

My experience is that most sales clerks are compass illiterate and have little navigation experience.  While looking at a compass ask the clerk to remove it from the plastic container/packaging.  Check the compass to ensure:

  1. The dial moves freely and does not stick.  There are no bubbles internal to the compass housing.
  2.  Information engraved on the base plate must be legible.  If there is a magnifying glass verify that it is clear and not scratched. 
  3. The tick marks on the dial are in two degree increments.  The tick marks should be readable.
  4. The base plate, rotating dial assembly, and mirror are not chipped or broken.  
  5. The sighting assembly hinge allows freedom of movement without excess side to side movement at the hinge .

 Packaging should clearly state that the compass is declination adjustable.  Adjustable compasses may have a small metal tool that allows for setting the declination.  If the packaging states that the compass has declination marking but does not use the word adjustable move to another model.

After purchase visit the website to determine the declination of the area the hiker will be traveling through.

Remember that the red magnetic needle will always point to magnetic north.  With a declination adjustable compass the rotating dial has been adjusted so that the information provided by the compass is now in degrees true.

Saturday, October 3, 2015

Is It Time To Replace Your Compass?

When should the hiker replace a compass:

  1. When there is a large bubble in the compass housing.
  2. When the compass body is scratched or cracked.
  3. When the sighting mirror is damaged or the hinge allows for excessive movement.
  4. When the compass polarity has been degraded.  For example, if you can identify that the compass is not providing accurate information (e.g., doesn't point accurately to true north.)   This could be true of an older compass.
  5. When lettering on the rotating dial is worn and abraded.
  6. When the rotating dial is stuck and won't freely move.
  7. When the magnetic needle has fallen off it's pivot point.

Thursday, October 1, 2015

Compass Interference

A magnetic compass needle’s movement is based upon the earth’s magnetic field.  That magnetic field and the movement of the magnetic needle on its pivot point in part, determine direction.

Ideally, there is no interference from any objects.

But that is not reality.  Nickel near the earth’s surface, rifle barrels and power lines all interfere with the compass’ movement.  What are the standoff distances that the hiker need observe?

I went to two publications to get that answer.  Camping and Wilderness Survival by Paul Tawrell (page 177) and GPS Land Navigation by Michael Ferguson (page 53) became my sources.

Metal Object
Power Lines
55-60 meters
55 meters
18-20 meters
10 meters
Telephone wires/barbed wire
8-10 meters
10 meters
Rifle/hand tools
2-3 meters
Pocket knife/binoculars/electronics
½ - 1 meter
2-3 meters
½ meter

Interesting data points to consider.  For example, if you combine the bottom three rows of information it becomes common sense to ensure the hiker’s gear is out of the way. 

Neither reference identifies the amount of impact these objects will have on the compass needle.  That is not practical for the average hiker.  It is the hiker's movement away from the object (.e.g., fence or car) to mitigate the error induced.

I would also offer that one should be careful how close to a compass electronics are stored in a pack.  I’d just keep it simple by stowing the flash light, GPS receiver and camera in a pack pocket/compartment away from the compass.

Note that GPS manufacturer Garmin recommends moving away from metal objects when calibrating the GPS receiver’s electronic compass.

Thursday, September 24, 2015

Pacing - Estimating Distance in the Back Country

Pacing and Estimating Distance

Many outdoorsmen measure distance in the backcountry by using a Global Positioning System (GPS) receiver.   GPS receivers are reasonably accurate, real time, and provide distance traveled and distance to a destination.
But what does the hiker do if they don’t have a receiver, the GPS fails or batteries die?
A proven method for estimating distance is known as pacing.  Pacing is not as accurate as the GPS receiver, but it can give a reasonable approximation of the distance traveled.  Together with a map and compass, pacing is an important component of evaluating a hiker’s track through the backcountry.  In darkness or periods of low visibility pacing helps to determine the hiker’s location through a process known as dead reckoning. 
Pacing is a method that begins with measuring one’s stride, with the intent of determining an individual’s length of stride. A pace is a measured two steps; a complete stride.  As illustrated below, every time the right foot hits the ground is one pace. Each pace (two steps) normally measures out to almost 50-60 inches.
Perhaps the best method to determine a hiker’s pace is to record it over a specific distance to determine an average.  Before embarking on the trail, the individual should develop a “pace average” over a controlled area first. 
For example, measure the number of paces for a known distance of 100 yards.  To achieve this, go to a high school foot ball field or track.  Walk along a sideline from end zone to end zone.  Count how many paces it takes to go 100 yards.  Do this eight times and record the total number of paces for each 100 yard event.  Determine the average for all eight 100 yard lengths completed.  The result is that the hiker may determine that the average 100 yard pace count to be 58 ½ paces.  (With children compensate and be mindful of their strides being significantly different, including a skip here and an off trail discovery there.)
Whatever the “pace average” may be, do keep the stride natural and smooth.  Don’t try to exaggerate and unnaturally lengthen the stride.
Don’t get too bogged down in the estimation of the accuracy of the average pace. Of larger importance is to understand the complexity of the terrain and how it will impact stride and a hiker’s “pace average”.   Anticipate strides being different.  Take the time beforehand to imitate a 100 yard course on sloping ground.  Further, try a 100 yard pace in soft soil and hard soil, smooth ground and rocky ground. Move to other locations once an average pace is found on a controlled level environment (football field).  Layout a 100 yard course on sloping ground. 
Pacing over long distance can become quite boring and the hiker easily distracted.  This is especially true when the pace count is in the hundreds.  Was that pace 545 or 554?  In such cases pacing beads may be a useful tool.  Pacing beads can be purchased from online venders or made at home using paracord and simple beads.  
A quick Google search will turn up several methods for using pacing beads.  For example,

Wikipedia states that “As users walk, they typically slide one bead on the cord for every ten paces taken. On the tenth pace, the user slides a bead in the lower section towards the knot. After the 90th pace, all 9 beads are against the knot. On the 100th pace, all 9 beads in the lower section are returned away from the knot, and a bead from the upper section is slid upwards, away from the knot.”

Pacing beads can be an important asset when Dead Reckoning (known as DR) with a map and compass.  Vigilant compass sighting and a steady “pace average” helps provide a rough approximation of both distance and direction when moving through the backcountry.

Wednesday, September 23, 2015

Problems on the Appalachian Trail

Hikers find a new threat to the Appalachian trail.
From FOX news:
When Jackson Spencer set out to tackle the Appalachian Trail, he anticipated the solitude that only wilderness can bring — not a rolling, months long frat party.
Shelters where he thought he could catch a good night's sleep while listening to the sounds of nature were instead filled with trash, graffiti and people who seemed more interested in partying all night, said Spencer, who finished the entire trail last month in just 99 days.
"I wanted the solitude. I wanted to experience nature," he said. "I like to drink and to have a good time, but I didn't want that to follow me there."
Spencer, or "Mission" as he is known to fellow thru-hikers, confronted what officials say is an ugly side effect of the increasing traffic on the Georgia-to-Maine footpath every year: More people than ever causing problems.

Wednesday, August 26, 2015

HELP - A Message in the Sand

 The following is from the UK's GUARDIAN.

A desperate message written in sand has saved the life of a British tourist who vanished in the Australian outback after he made 'the stupidest decision of his life'.

Geoff Keys, 63, was stranded for two days in the Jardine National Park in far north Queensland, when the self-described explorer got himself lost when trying to reach an isolated part of the park.

Mr. Keys was barefoot, alone, without food and fearing for his life as he tried to retrace his steps and return to safety. However, the Briton wound up more than 12 kilometers from his camp and, in a moment of madness, tried to swim to the Eliot Falls.

The desperate message left by Geoff Keys, the British tourist who survived two days lost in the Australian outback
In an act of desperation, the 63-year-old from Kent, scratched an SOS message into the sand - hoping someone would spot it.

The carving read 'HELP 2807' and had an arrow pointing downstream to where Mr. Keys was resting. 

'It seemed a good idea to help myself as much as possible so I got out of the water, found a stick and wrote a message in the sand, just in case the helicopter came down that way,' Mr Keys said.

'HELP. 2807. –>. Help, today’s date and my direction of travel. I thought this would be enough to get any helicopter that saw it looking in the right place.'

To read the complete post of Mr. Key's ordeal go here. 

Navigation Term of the Month - True North

True north refers to the north pole; significantly different from the magnetic pole.  True north
is our principle geographic reference.  True North is located at the top center of the earth.  Topo graphic maps are laid out with a clear reference to true north.       

To keep my navigation simple I use a compass (Silva Ranger, Suunto M3) that can be adjusted to true north  and I set up my GPS receiver to report in degrees true.

This way I match my map with my compass and GPS receiver such that I am on the "same page" with all my navigation equipment.  

The difference between true north and magnetic north is called declination; it changes over time and it varies in relation to the hiker's location