Magnetic Declination

“Declination: A Noun. The horizontal angle between the true geographic North Pole and the magnetic North Pole, as figured from a specific point on the Earth.” www.dictionary.com

 Declination is a term that causes “brain cramps” for many of my students in my map and compass classes. When I mention Magnetic Declination eyes roll.

The web site www.magnetic-declination.com has an excellent discussion of what declination is and what causes it:

“Magnetic declination varies both from place to place, and with the passage of time. As a traveler cruises the east coast of the United States, for example, the declination varies from 20 degrees west (in Maine) to zero (in Florida), to 10 degrees east (in Texas), ......the magnetic declination in a given area will change slowly over time, possibly as much as 2-25 degrees every hundred years or so.......... Complex fluid motion in the outer core of the Earth (the molten metallic region that lies from 2800 to 5000 km below the Earth's surface) causes the magnetic field to change slowly with time."

Land navigation is based on the relationship to the North Pole; also known as “true north.  The measure of degrees of direction in relation to true north is called “degrees true.”  Maps are laid out in degrees true.  Land features (buttes, mountains, streams) on a topographic map are in reference to degrees true.  By that I mean the bearing from one mountain peak to another will be referenced in degrees true.  The map below illustrates that point. 

Magnetic compasses do not point to true north (the North Pole); the magnetic needle points to an area that could be considered the magnetic North Pole. 

As illustrated below, declination data can be found in the diagram at the bottom of a USGS topographic map, (on some commercially produced maps it can be hard to find.) 

Because declination changes over time, I recommend that map declination information be verified at www.magnetic-declination.com.   This is essential in the Pacific Northwest where maps are notoriously out of date in terms of road,  and city data.

So, how do we make this simple?  How do we convert magnetic to degrees true?

I could do the math.  In Oregon, where I live, the magnetic declination is 15.6° East declination.

My recommendation: have the compass do the work so that there is no confusion with the math.

To do this, I need to choose a compass that can be adjusted for declination.  Some examples are the Silva Ranger or the Suunto M3.

With one of these compasses, the compass dial or housing is adjusted and rotated manually.  Both the Suunto and Silva Ranger come with a small, flat adjusting tool.  Consult with owner’s manual that came with the compass.

If declination is Easterly (Western U.S.) I will rotate the dial causing the baseplate’s orienting arrow to move in a clockwise direction.

   If declination is Westerly (Eastern U.S.) I will rotate the dial causing the baseplate’s orienting arrow to move in a counter-clockwise direction.

Now, adjust the dial and align the red magnetic needle on top of the orienting arrow (the red arrow engraved on the baseplate) the compass will provide directions in degrees true.

Managing Your GPS Waypoints

Outdoor Quest //Blake Miller image  Lots of things can happen to a GPS Waypoint or data file.  You can put data in. You can take data out.  You can lose it (the GPS breaks or the wrong button entry is selected.)  But be careful, far worse, too much data can make your navigation difficult.  In my land navigation class I stress keeping your navigation simple.  Frequent and simple Waypoint management is essential to GPS use.  When it’s time to return to the truck, it should be obvious what GPS Waypoint to select.   Dump the junk before the start of a trip.  As you leave the trail head your GPS should have only necessary data saved on your GPS.  That Waypoint for the fishing hole is important but needs to be saved elsewhere.  Start by deleting Waypoints that really are not needed.  Free those data bites to the atmosphere.  To save your “got to have, must save Waypoints:”               1.            Use Garmin’s “Trip and Waypoint Manager.”  It probably came with your GPS.  It can also be purchased from Garmin for about $30.00; www.garmin.com.  Down load those Waypoints to your PC.  2.            If you don’t have the Garmin program, consider “Easy GPS.”  It is free and available at www.easygps.com.             3.            Log the important data in a notebook.  Electronic storage allows you to save Waypoints and track data (that bread crumb trail on your map screen.)  Further, you can upload old Waypoints another day for a trip to that special fishing spot.  This data can also be down loaded into your friends GPS too.  It can also be uploaded to your new GPS in the future.  Remember though; when you receive or transfer GPS Waypoint data always verify that you have the compatible map datum and coordinate system set on your receiver.  Finally, give important Waypoints a name.  It’s easier to remember a GPS Waypoint named “CAMP” instead of 21 (or was it 25.)

Your Backcountry Travel Plan

There are lots of articles and posts about letting the responsible person know about your travel plans.  Should you not return home on time they are the trigger to begin the search process.


This may be the most comprehensive plan made yet!!!

After the loss of James Kim in the Oregon back country in 2006 I wrote a hiker's trip plan and posted it on myblog.  I had input from several valued sources.  I wanted something better for the wilderness traveler than a note to a neighbor.  My intent was to provide the search responders something valuable to go by.


In far too many SAR missions, the reporting party has little information for the searchers to go on to begin their search.

My plan can be found here.  It is a basic .pdf form.

Suggestions are certainly welcome.

911 Call center

Still, that responsible person plays a huge role in contacting authorities to begin a search.  My recommendation would be to pick a person that will make the 911 phone call without hesitation.

Travel safely.

Power For Your Gear in the Backcountry

A few years ago I posted a short article about power for your gear: (.e.g. GPS receivers.)  Here is an update.

A frequent question that I get is how long do batteries last?  What can be counted on for GPS battery power.

From my experience the answer is about 12 hours when used continuously.

I have noticed that the electronic "battery power meter" provides OK information. The four  power bars last reasonable well initially.  But after the receiver has been on for most of the day, I have noticed that the GPS battery power goes from three bars to two and then one quite quickly.

I keep my GPS powered on all the time.  I l do this to evaluate track data later.  For example, when I am in the field hunting I discard the batteries at the end of the day, replace with new one, and calibrate the compass. I find it handy to replace batteries at camp rather than going through the process in the morning's darkness.  I like to just grab and go in the morning.

I particularly like the Duracell and COSTCO batteries. Rayovac batteries but do not last nearly as long as the others.

For short duration hikes I will use the rechargeable ENELOOP batteries.  I bought my set at COSTCO. I find that the ENELOOP batteries are very versatile, retain the charge a long time, are simple to charge and quickly recharge.

Small sets of 4 are available at some of the big box stores too but they are not cheap.

 I recommend that if your gear uses AA batteries predominately then stick  to those rather than having a mix of AA, C and AAA.

Ten Essentials - Include a Whistle

The Ten Essentials is a list of ten very basic items that a hiker or hunter should carry in a day pack; visi tThe Mountaineers Ten Essentials to get their traditional list. 

Consider this to be the foundation of your pack.

While sitting at a desk the backcountry hiker would consider this a very slim list.  Many of the essentials can be carried in a fanny pack.

One item I'd add to the list is a whistle.

Each year, lost hikers a located by using a whistle.  Of course one can yell.....for a short time; until one's voice is worn out.  Whistles require no batteries, can be really loud and take up little room. Ten essentials whistle.  I like the Fox 40 and I like to have a whistle made of plastic and is florescent/hunter orange.

Keeping it simple, here is what  is on amazon.com.  Sportsman's Warehouse has them too.

Food For the Hiker/hunter

There is a new and very favorable dried food option available to the backcountry hiker or hunter.

Julie Mosier has just introduced her line of best quality  dried  available through her web site at www.https:foodforthesole.co.

Food for the Sole doesn't have a ton of salt in it.  Selections are packaged compactly, light  and take only a small amount of water to hydrate.

And you can use cold water to hydrate.

This is a great product.

Calling 911

The following post has some very good information about calling 911.  In my county of roughly 100,000 citizens the emergency call center receives over 300,000 calls a year. 

The following post is from www.wikihow.com.

911 is meant to connect you to help. In some areas, it is for serious emergencies only. In other areas, it is for anytime you want police or fire to respond. KNOW what the expectation is in your area. If you are not sure, call them and let them know it is not an emergency. They can let you know if you should be calling a different number.

Get on the line, and let the 911 dispatcher know what the call is about. Answer any questions they have as best you can, and stay on the line follow any instructions they give you while waiting for help to arrive.

They will ask questions to assess the level of response and the speed of response that is needed.

Be ready to tell them: - Your name - The number you are calling from and a call back number if that is different. - Where you are and where help is needed. Not all cell phones or VOIP based land lines give accurate locations. If it is not an address, you need to be aware of how they can find you, even if that means that you get them to a location that they can find and have a person to direct them the rest of the way. - Who needs help - What help is needed. If this is an emergency, tell them everything you know (how they got injured, what is injured, their level of alertness, any medical issues that are known). This is what they use to determine if a squad car can casually cruise through the area or if they need to get police, fire, ambulance all headed out with lights and sirens.

Stay on the line. They may ask you for updates or put an emergency res-ponder on the line to give you assistance in handling things before they get to you.  For more info on this topic go to:

Calling 911:

UTM Grid For The Hiker

Universal Transverse Mercator (UTM) is a grid system that describes a person’s geographic location in the backcountry.  It is simple to understand and use because:

1.    It is intuitive -  it’s concepts can be understood quickly,

2.    It can be easily self taught,

3.    Young hikers grasp this system easily,

4.    A location on a map can be quickly determined, and;


5.    It is a selection option for Global Positioning System (GPS) receivers.  

A navigation grid is a reference system developed by cartographers that can be used to plot a geographic position on a map.   There are many grid systems available for use such as Latitude and Longitude and Universal Transverse Mercator (UTM).  Several countries have their own national grid system. 

The UTM system is just like a Cartesian Grid.  For example, the grid position below is just 2.2 units over and 2 units up.

 To understand the complete grid we will start by observing that the globe is divided into 60 zones.  Each zone is 6° of longitude wide.  Each zone runs north and south; 84° north to 80° south.

The image below highlights the UTM zones in the continental United States.

UTM grid consists of Northings and Eastings.  The image below highlights the complete layout of a UTM zone.  Notice the Central Meridian that runs north and south through the zone.  Like longitude, this meridian runs from pole to pole.  All values for measuring position are in meters.  At the equator the zone is 500,000 meters wide.  The width of the zone is described by Eastings.  Northings run north or south from the equator; again all values are in meters.

UTM coordinates are presented such that the zone is listed first, followed by the Easting and then the Northing.

                                    10   0524120 E  4891555 N

The hiker should think of a grid as a series of defined squares on a map (see below.)  On a 1:24,000 scale (7.5 minute topographic quadrangle) the grid lines are 1000 meters apart; north or south the spacing between grid lines is 1000 meters.

The coordinate values are known Easting’s (vertical lines) and Northing’s (horizontal lines.)

Easting values increase moving from left to right and Northing’s increase from bottom to top.  Coordinate values are always positive.

 Every location will have a zone identifier.  On the map above the zone is linked to the Easting value and is the first set of numbers.  In this case the zone identifier is the number 10. 

 

 The letter “T” seen above is a secondary, horizontal (east-west) identifier.  I personally pay little attention to it in my backcountry trips.

All USGS maps identify the zone in the title block at the bottom left of the map.  Note that on some commercial maps the UTM zone identifier may not be in the title block and can be hard to find.

The UTM coordinate can now be refined to a meter.  Again the spacing between the grid lines is 1000 meters (1 kilometer).  On the maps below, the tick marks between gridlines are in increments of 100 meters.  The hiker can then interpolate the distance between the tick marks.  

The position of the large X on the map above would be described as:

            10 5 25 270 East (the green line)

            47 91 180 North (the red line)

The final three places will always be expressed (10 5 25 270 East.)  The value 2 is in units of hundreds, the 7 is in units of 10 and the 0 is in units of 1’s.   Thus, 50 meters would be written as 050. 

Every point on a map (e.g., a mine, an intersection, a camp site, etc) can be described using UTM coordinates to the accuracy of one square meter.

I recommend consider carrying a small plastic ruler or other suitable straight edge when accuracy is important.  For general hiking and backpacking, one can quickly estimate a current position in the backcountry without other map tools.

UTM coordinates of a destination taken from a map can be easily saved on a GPS receiver.  For example, to do this the hiker “marks” a waypoint and then moves the backlit bar (yellow shaded area) from “save” to the “location” data field.  The “location” data field is then edited per the receiver’s instruction manual.

  

A fine reference for more practical information about UTM grid is Lawrence Latham’s book GPS Made Easy.  Chapter 5 has an easy to understand tutorial on this grid system; that’s how I learned it.

Getting Accurate Compass Readings

I found these recommendations a while back when I was researching techniques for using a magnetic compass.  A small error when using a compass can result in a significant error in measurement on the ground.

To obtain accurate readings when using a compass:

• Ensure the compass has been adjusted for declination. 
• Hold the compass level and steady so the needle swings freely.
• Hold the compass about waist high in front of the body, except when using a compass with a sighting mirror or a sighting type compass.
• Raise and lower eyes when taking a bearing, do not move your head. Always use the same eye when taking bearings.
• Directly face the object that is being measured.
• Magnetic fields will give incorrect compass readings. Avoid taking readings near magnetic fields such as steel, iron (ferrous metals), vehicles, rebar, and clipboards. Even belt buckles, glasses, and rings can interfere with the compass reading.
• Take bearings twice. 
• Adjust for magnetic declination as appropriate.
• Follow the direction of travel arrow, not the compass needle, when walking a bearing. Always follow the line indicated by the compass rather than relying on judgment as to the direction.
• Use back bearings to ensure you are on track when navigating.
  

  
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Taking Good Care of a Compass

A few thoughts on taking care of your compass and what to look for before you go hiking in the backcountry.

Remember that the correct operation of the compass is dependent on the action of the magnetic needle to guide the hunter through the backcountry.  Lots of items in a pack and clothing can effect the needle.  Most understand that ferrous objects such as a rifle barrel, belt buckle, and car keys will deflect the magnetic needle.  Still, take a good look at what is in a day pack.  The batteries from the GPS receiver and a flash light may cause a compass needle to move.

High tension power lines and a vehicle’s electrical system may also cause a magnetic needle to deflect.  Moving a few steps from the vehicle should be sufficient.  One may have to move over one hundred feet from the power lines to avoid deflection.  (GPS Made Easy, Michael Ferguson.)

Some locations will have a high concentration of iron near the surface.  This is known as “local attraction.”  Such concentrations will cause the needle to move too.  Unlike declination, moving away from the immediate area may cause the deflection to stop.  The local Bureau of Land Management or Forest Service Office should be able to identify areas affected by local attraction.

 I recommend that a compass be stored away from electronics (e.g., GPS, radios), batteries and many metallic (knives, saw) objects found in a pack.  I don’t recommend going overboard on this but a compass could simply go in an exterior compartment, a shirt or coat pocket.  Attaching a brake away lanyard to a compass so that is worn around the next is a viable option. This would apply during the off season too; a little separation is a good thing.

It is possible for the magnetic needle to lose its polarity.  This is a function of time and manufacture.  With research, one can learn how to restore the magnetism.  That said, with the modern liquid filled compass this is probably more trouble than it is worth.  Occasionally, check the alignment of the compass.  In the small town where I live, residential streets are aligned true north and south.  Standing on the curb on such a street provides a quick verification of how the compass is working.  To me verification means that the compass direction will mirror that of the street; if the street tracks true north then the adjusted compass should provide a bearing to true north.

At the end of the hiking or hunting season take a look at the compass.  Flush away dirt or sand that may be on the baseplate or sighting mirror.  Look for bubbles that may appear internally and adjacent to the compass needle.  A small bubble may not be something to worry about but a large bubble may impact how the needle swings and moves.  A compass with a large bubble should be permanently removed from the hiker’s kit.

Lastly, keep in mind that a quality compass will retail for $20 or more.  Also, a quality compass can be mechanically adjusted for declination.  Such a compass is a precision piece of equipment.  This is especially true of the Silva Ranger style or the Brunton Eclipse models.  Note that I am prejudice (won’t buy them) towards the cheap stuff found on the racks of the major box sporting goods stores.  If a hunter is willing to spend hundreds of dollars on a rifle scope why not spend a bit more for a decent compass; it can make a huge difference.