Map, Compass & GPS

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

Thursday, December 31, 2015

Navigation Term of the Month: Map Scale.

Topographic Map - Scale

By Blake Miller

Dictionary.com defines map scale as:

“A ratio which compares a measurement on a map to the actual distance between locations identified on the map.”



A topographic (topo) map’s scale information is located at the bottom center of the map.  Other maps will generally have scale information in the large map key that outlines many of the features and data printed on the map.

The map scale for a United States Geologic Survey (USGS) 7.5 topo minute map is highlighted below.



Think of scale as your “zoom setting” as you would on a camera.  The smaller and tighter the scale the more detail you will find.  The topo above has a scale of 1:24,000.  A map of a national forest may have a scale of 1:126,000.  The forest map will not have the detail but will cover considerably more area.

Tuesday, December 29, 2015

What Is An Azimuth?


An azimuth is the angular direction to an object.  Azimuths are described commonly in degree increments from either true, magnetic or grid north.

In the world of recreational navigation, GPS receiver operations and orienteering the use of the term “bearing” has become synonymous with azimuth.

Azimuth direction is measured from north clockwise in 360° increments. The point from which the azimuth originates is from the center of an imaginary circle.  This imaginary point is the operator.


Azimuth can be measured with a magnetic compass, a map and by rough estimation using the sun and North Star.



Azimuths can be expressed in degrees true and degrees magnetic.  Degrees true uses the north pole as the principle reference while degrees magnetic refers to reference from the magnetic pole.

Outdoor Quest Image
For more information on bearings and azimuth read Making Sense of The Declination Diagram.

Thursday, December 17, 2015

Addressing Hearing Loss

Addressing Hearing Loss

Some families play board games; some take an annual trip to the beach. Our family traditions were a
little bit different. I completed my first summit of the 14,411-foot Mount Rainier when I was 12 years old – something normal by my family’s standards. Some of you may know my uncle, Jim Whittaker, the first American to summit Mount Everest. Or my dad, Lou Whittaker, the founder of Rainier Mountaineering.

Along with a love of climbing, I inherited from my family a deep passion for life and adventure. As my father was famed to have said, “When it comes to dying, I want to know what it is like to have really lived.” I have translated that spirit into everything I do in life – from mountaineering, to making music, to filmmaking.

About ten years ago, though, my wife Sarah started to notice that my love of adrenaline may not have been the only thing I’d inherited from my dad – it seemed my hearing, like his, was starting to go.

At the time, I didn’t really notice any of the effects of my declining hearing, so I pretty much waved it off. And, then, it become noticeable. Within a few years, it was more often than not that I had to ask a client in climbing school to repeat a question. It was becoming a bit more difficult to find the exact right sound when I was recording with my band.

Between my dad’s hearing loss and my lifelong love of loud music and power tools – it wasn’t a huge shock I had found myself at this point. But I can’t lie – I was not thrilled at the thought of having to get a hearing aid. My reluctance was not because of any stigma attached to hearing aids, but more so because of the hassle of setting them up. I knew you have to go into the audiologist repeatedly to get them working just right. Even then, with all of the various environments I am in, I knew there was no way that one setting would work across the board. To add to my hesitation, in addressing my dad’s hearing loss, it didn’t seem like his hearing aids had helped him at all. Particularly in crowded environments, his hearing aids just amplified sound, making the environment overwhelming.

I didn’t want that, especially since I was still regularly climbing and guiding climbs up the mountain. If a hearing aid just picked up and amplified the sound of the wind, it wouldn’t do much good for me in that setting – one of the environments where my hearing was the most important to me. So, for that reason, I kept putting off addressing my hearing loss.

That was, until last year, when I was introduced to the ReSound LiNX. I had mentioned the idea to my audiologist before but it wasn’t yet in existence – the idea of being able to easily adjust the audio settings of a hearing aid on my own. The LiNX was the first ever Made for iPhone hearing aid, which meant it communicated directly with your phone and could be adjusted wirelessly through an app.

As an audio engineering geek, I was hooked right away. Through the ReSound Smart app, I could use my iPhone to adjust my hearing aids’ volume, bass and treble, and direction of sound amplification. Calls and music were streamed directly through my phone to the aids. The first day I was fitted with the ReSound LiNX, I remember hearing the sounds of rain squelch under my shoes, and my shoes subsequently squeaking on the tile when I got home – sounds I hadn’t even realized I was missing out on.


Now – wearing ReSound’s latest, the LiNX2 – I can hear a pebble falling on the mountain. My clients tell me my hearing is bionic. Sometimes I think about my decision to address my hearing loss. Like any other challenge in life, I took it head on, now sporting a bright red hearing aid behind my ears. And, as someone who isn’t ready to slow down at all, I sure am happy that I did.

Sunday, November 29, 2015

Terrain Association


“A good view will help to form a picture of the shape, the patterns and grain of the land itself.  High ground will tell a story of the geological formations and erosion.”
                                    The Natural Navigator by Tristan Gooley

Terrain association is a key step in land navigation.  While the topographic (topo) map identifies terrain features through the use of contour lines, colors and symbols, terrain association is a process of confirmation of map to land features.


In the field a key step in terrain association is to orient the topo.  Orienting a map is a starting point to identify where I am, where I want to go and where I have been.  When oriented, map north will match geographic north on the ground. For information on how to orient a map read my supporting post.

 I orient my topographic map (topo) before I leave the trail head and at regular intervals during a hike.
It is a process where I involve both map and compass.  Of course, orienting a map can be done without a compass and done visually.  I find using a compass takes just a tad more time and the more hands on time with the compass the better. 

A key component of terrain association will be the evaluation of the information provided by the contour lines.  Contour lines identify five key terrain features that include hilltops, valleys, ridges, depressions and saddles.
“Match the terrain to the map by examining terrain features.”
                                    US Army Field Manual FM 21-26 Map Reading and Land Navigation
Gain a clear view of the land in the immediate area before comparing map to ground features.  If needed get an elevated view of the surroundings.
While looking at the map, I break down the terrain and lay of the land into two components that I refer to as pathways and boundaries. 
Pathways make up my route through the backcountry.  Pathways are trails, old “jeep roads,” government roads (e.g., Forest Service and Bureau of Land Management gravel and unimproved roads.)  Not all trails and roads are pathways.  In an area lacking trails and roads, an open area clear of significant vegetation may be a pathway.  Similarly, a valley or ridge line might be a pathway too.  Importantly, the pathway will be in the direction of desired travel.  Finally, the hiker needs to ensure the pathway is safe and he is physically up to the task. 
Trail guide books are an excellent source for finding a pathway.  Many of the newer publications offer coordinates for the GPS receiver, map views and a description of the recommended route.

Boundaries are major land features that help guide the hiker along his path too.  They are features that provide containment and may prevent the hiker from going far off track.  Boundaries can be rivers, streams, rail road beds, roads and large features such as a mountain range or ridge line.  Boundaries keep the hiker within the route of travel.  For example, if a stream is crossed then perhaps the boundary has been violated.  

Figure 1 In the image above the blue line is the pathway with the borders and boundaries in red.

In the image above the blue line mirrors an existing trail and is a pathway.  The two red lines border steep terrain and are the boundaries for this hike.

Start the terrain association process at home.  By reviewing the route on the kitchen table one begins to develop a mental map.  Maps reviewed with trail guides and conversations with those knowledgeable of the area improve the hiker’s familiarization of the backcountry pathway; this is the detail that improves and supports navigation.  The refined mental map aids in the correlation process while in the field.

Practice and frequent review makes the task of terrain association simpler over time.  Involve children in the process too.  They will be your future navigators.


                                                                                                    

Wednesday, November 25, 2015

Guests

My guests are arriving early for Thanks giving dinner.

Tuesday, November 24, 2015

Suunto Compass Review

A good friend alerted me to Sectionhikers' post about the Suunto M-3D compass.


"The Suunto M-3 D Compass is a baseplate style adventure compass with a declination adjustment that is optimized for use in forested or mountainous terrain where you can rarely see your destination. I’ve been using mine for 4 years, ever since I became really interested in off-trail hiking and navigation and started teaching those skills as a instructor for the Appalachian Mountain Club."


To read the complete post go here.


The Suunto M-3D is a super compass.  Think of it as a rugged scientific instrument.


This is a great choice for a Christmas present.

Wednesday, November 18, 2015

GPS Battery Power

In 13 years of teaching GPS classes I have had very, very few reports of a GPS receiver breaking or failing electronically. What I do hear about is battery power draining at the worst time.
I’d offer a few suggestions:


  • Batteries will generally last for a reported 20 hours of continuous use; more on that shortly.  If you just turn it on, mark a waypoint, and turn the receiver off, the batteries will last quite a while.
  • I prefer the Duracell and COSTCO alkaline batteries.  I have found that cheap batteries don’t last as long and require replacement more frequently.
  • If a GPS receiver can use Lithium batteries then consider that option and do check the owner’s manual.  Lithium batteries are more expensive but last longer and work better in cold temperatures (down to -40°F).
  • Carry a spare set of AA batteries.
  • I keep fresh batteries in my GPS all the time.  That said, because of my SAR responsibilities and the frequency of my trips, fresh batteries are always loaded.  It’s my personal preference that “works for me.”
  • If you have an older receiver such as the Garmin 12, keep batteries in it always.  The four AA batteries keep the internal lithium battery charged.  The internal lithium provides power to retain saved waypoints and tracks.
  • Features such as the backlight, audible tones and electronic compasses drain a set of batteries.  On many models the electronic compass can be turned off by pressing and holding down the page button.  Manage your power needs.
I don’t have a baseline for rechargeable batteries.  My suggestion would be to keep extra’s on hand and really “wring them out” over a full day to see how well they work.  Do this before your trip afield; remember, it has to work for you.

I keep my GPS powered up all day when in the backcountry.  I download my track and waypoint data at the end of a hike to my Terrain Navigator software. This gives me the best historical record of my outing.  Usually batteries become drained after a full day and it just easier  to change them out as I get my gear ready for the next day.  


A fully charged GPS is a wonderful tool that complements your backcountry experience. Remember, even though you have the latest and best receiver, always take that map and compass on every trip.

Monday, November 16, 2015

Dangerous Weather in the Backcountry


In the field forecasting is an important skill for the backcountry hiker.  Learning the basics is an important first step.

Let me begin by stating that forecasting begins at home.  Monitor the local news and the cable weather channels to get a broad, general idea of the weather conditions before hitting the trail.  Further refine that information by checking inter net sources such as www.wunderground.com and the National Weather Service’s site www.noaa.gov.
My “go to” reference is Northwest Mountain Weather by Jeff Renner (published by the Mountaineers.)   Renner is a professional meteorologist and broadcaster, an outdoorsman
and flight instructor.  Northwest Mountain Weather provides a superb overview on how “the weather works” in the Pacific Northwest.  Uniquely focused to this region, this book provides an overview on climate and weather, local weather patterns, snow and avalanche conditions, and provides many charts and data sources.  My favorite part of the book is Chapter Seven’s “Field Forecasting Guidelines.” This chapter identifies what to watch for and monitor while in the backcountry.  

The balance of this post will focus on what to consider about hiking during periods of thunderstorm activity.

The dark clouds of a thunderstorm provide a strong sense of mass and energy.  They can be seen a long way off.  Avoid them when possible.

As a storm develops you will notice that the clouds may change shape, grow taller and darker.In many cases an anvil shaped cloud growing tall and developing a distinct leading edge maybe observed.  This is a sign that a storm is on the way.

Lightning is the predominant killer associated with a thunderstorm.  Roughly 40 people are killed each year and approximately 240 are injured.  Visit the National Weather Service’s site for more information about lightning safety; http://www.lightningsafety.noaa.gov/medical.htm

The ideal action to avoid the danger of a significant storm is to get out of the weather.  Leave the field for the safety of a building or a car.  Caves can provide shelter but must be deep and dry.  A shallow cave offers almost no protection.
Renner’s guide lines and actions include:

            “Do watch for cumulus showing strong upward development.
            Do choose a campsite uphill from valley floor.
            Do get away from exposed areas, pinnacles, peaks.
            Do get away from water.
            Do seek low ground in open valleys and meadows.
            Do move at once if hair or scalp feels tingly.
            Do not stand under trees.”[1]

Wilderness Survival trainer Peter Kummerfeldt amplifies Renner’s comment by adding the following:

            “Be proactive – don’t wait until you are getting wet to suspend outdoor activities.
Don’t be connected to the tallest object in the area.  If caught outside, move into low trees of even height and stand away from tree trunks.  Stay away from isolated trees.
Water is a great conductor of electricity – get out of the water at the first sign of a storm developing.”[2]  (For more information visit Kummerfeldt’s web site, www.outdoorsafe.com.)

Thunderstorms have the potential to deliver large quantities of water.  Look for higher ground and stay out of stream beds that may flood significantly and without warning.
I monitor my GPS receiver’s barometer.  I change my elevation plot to a pressure plot and leave the receiver on.  Even though a GPS receiver may not be the most accurate it is the plot’s trend over time that I am concerned about.  Should I see the pressure drop noticeably I’ll take shelter or return to my vehicle.

The key is to stay alert and make a plan of action when a storm approaches. 
I previously posted a short article about using your GPS to monitor barometric pressure while in the backcountry; go here to read the post.  I thought it might be worthwhile to cover a few other topics about in the field observations.  This post is about thunderstorms.




[1] Jeff Renner, Northwest Mountain Weather, (The Mountaineers, 1992), p 100
[2] Peter Kummerfeldt, Surviving a Wilderness Emergency, (OutdoorSafe Press, 2006), p56-57 

Monday, November 9, 2015

Magnetic Compass Common Mistakes

The compass maker Brunton has listed the top 5 magnetic compass common mistakes when using a compass.
  1. Having the map 180 degrees incorrect when taking a bearing ie getting north and south mixed up.
  2. Using a compass near metal objects, or near electronic items, causing the magnetic needle to be inaccurate.
  3. Looking at the map all of the time and not looking at visual clues in the real world.
  4. Losing concentration and walking too far when you get to your point, falling victim to confirmation bias – the tendency to see things that confirm you are right, but miss things that show you are wrong.
  5. Only carrying one compass with you. If one breaks you are stuck.
Make sure you don't make one of the magnetic compass common mistakes.

Sunday, November 8, 2015

Contour Lines of a Topographic Map


Contours are the thin brown lines that snake across a topographic (topo) map.  Contour lines connect equal points of elevation such that every point on a specific line will be at that elevation above sea level. 


 



Contour lines are distinct and separate from lines for roads, coordinate systems (e.g., latitude and longitude) and trails.  Man made features like roads and buildings are black.  Contour lines are brown.  By adding elevation data to the map contour lines provide a three dimensional view of the terrain.  These lines provide shape and a sense of texture. 




The graphic above uses shading and electronic editing in an attempt to gain a three dimensional view of the terrain.  Compare the two maps.

Here are a few “keys to the kingdom” of reading these the brown contour lines.

There are two primary types of contour lines, index and intermediate lines. 

The dark brown, wider lines (below) are “index lines.”  The numbers adjacent correspond to altitude along the line.




For example, if the hiker locates his position on the topo and its right on top of the dark brown line with 5200 printed on the line, the altitude at that point is 5200 feet.  Consider the altitude to be the height above sea level.

The faint brown lines between the index lines are “intermediate contour” lines (see graphic above.)  Critical to intermediate lines is the specific elevation change between the lines.  This is known as the “contour interval.” The contour interval could be 10 feet, 20 feet or 200 feet; it just depends on the scale of the map and terrain.  To find the contour interval on a topo go to the bottom of the map or to the map key/index.  On a United States Geologic Survey (USGS) 7.5 minute topo map it will be at the bottom center of the map.  In the graphic below, the contour interval is circled in red.




In the small map above, look at Browns Mountain.  The spacing between the intermediate contour lines represents an elevation change of 20 feet.  Notice that the index lines are spaced five contour intervals apart or 100 feet between index lines.

Contour lines (index and intermediate) can provide a view of slope and pitch, depressions, ridge lines and level ground; the highs and lows of the earth’s surface.
The contour lines at Browns Mountain are close together and represent a steep increase in elevation.  Lines close together can indicate a peak, hill, ridge line or a cliff.

The contours of the land area to the left or west of Browns Mountain are spaced farther apart.  Such lines indicate flat ground like a meadow or plain.  Lines far apart make for gentle slopes and flat ground.

Ridges, valleys, and streams are represented by contour lines too.  A line’s shape identifies these land features.  For example, a valley’s shape is formed by a collection of “v’s.”  Tips of the v's point toward higher elevations.  Look at Alder Creek on the map below.  Note that the creek bed is in the bottom of a valley and water flow is from higher elevation to lower.


The contour lines that shape Alder Creek have v’s that point to higher altitude.  Look closely at the index lines and try to determine the elevation change as the creek flows north.

Contours shaped like a v or u, pointing toward lower elevation denotes ridges.  Notice the shape of the contour lines to the right and east of Alder Creek.  The v’s tips point toward lower elevation.  In fact, the v’s have become more like expanded “u’s.”



For more information about contour lines visit www.landnavigation.org or search the internet for the “World of Teaching – Topographic maps” (a very fine power point presentation.)






Monday, October 19, 2015

Celestial Navigation


I learned celestial navigation back in the 1970's. My son is a serving naval officer and told me several years ago that the US Navy no longer used or practiced celestial navigation.

That policy is in for a change.

The following article is from Defenseone.com and is written by Steve Mollman.

"Satellites and GPS are vulnerable to cyber attack. The tools of yesteryear are not.

Sometimes old school is best. In today’s U.S. Navy, navigating a warship by the stars instead of GPS is making a comeback.

The Naval Academy stopped teaching celestial navigation in the late 1990s, deeming the hard-to-learn skill irrelevant in an era when satellites can relay a ship’s location with remarkable ease and precision.

But satellites and GPS are vulnerable to cyber attack. The tools of yesteryear—sextants, nautical almanacs, volumes of tables—are not. With that in mind, the academy is reinstating celestial navigation into its curriculum. Wooden boxes with decades-old instruments will be dusted off and opened, and students will once again learn to chart a course by measuring the angles of stars."


Read Mr. Mollman's complete post.

Wednesday, October 14, 2015

Important Considerations When Working with Maps


When working with maps there are some key points to remember, especially when using a map in conjunction with a compass and a Global Positioning System (GPS) receiver.

Datum

Maps made based on a datum (horizontal and vertical).  Datum is the origin from which all points on a map are measured. Three primary datum have been used to develop maps in the United States.  These are:

  • North American Datum of 1927 (NAD27)

  • North American Datum of 1983 (NAD83)

  • World Geodetic System of 1984 (WGS84).

Datum is a mathematical model that accounts for developing a map from a spheroid (the earth) to a flat map.

When using a GPS receiver the datum must be set to match the horizontal datum on the map. If the datum does not match, there will be errors when plotting data on a map.

Map datum information is found in the title block at the bottom left corner in the margin of a USGS map.  Other maps (e.g., US Forest Maps and commercial maps) seemingly provide datum in rather random locations. The hiker will have to scan the map to find this information.

Geographic North

Maps are laid out in relation to geographic North (also referred to as the north pole or true north.) This is important to remember because the traditional magnetic compass provides information based on magnetic north.  Magnetic north changes over time, while geographic north does not change. The difference is referred to as magnetic declination. When using a compass and map together the hiker must account for this difference.   Because of this I recommend that the navigator have an adjustable compass such as the Sylva Ranger.

For more on declination go here.

Maps Are Not Perfect

For a map to be considered reliable and accurate, map symbols marked on a map must be in proper relation to known landmarks or positions located on the ground.  In 1947, the “United States National Map Accuracy Standards” were established as the standards of accuracy for published maps and are currently in effect. The standards require a stringent percent of accuracy within centimeters of both location and elevation of points tested. However, even with these standards, maps are not absolutely accurate because:

  • Maps represent a curved and uneven surface that is drawn on a flat piece of paper, which results in a distorted picture.

  • There is a margin of error (human error and inadequate survey procedures) in surveys that were used to create maps. Also, there are factual matters (errors such as names, symbols of features, and the classifications of roads or woodlands); sometimes the information is wrong and names and features change.

  • If a map has been photocopied, it most likely is not to scale.

  • Maps editions are dated and not current.

Maps do not accurately represent the ground surface

Topographic maps provide an overview of the ground surface.   A USGS 7.5 minute map uses  a scale of 1:24,000.  This means that 1” of map distance equals 2000’ feet on the ground.  1square inch on the map is equal to 91 acres on the ground.
The symbolic information provided by colors provides only a general description on the ground.  For example, green coloration refers to vegetation such as forested areas.  But what color does not tell you what is the surface really like?  The map doesn’t tell the hiker if the area is full of brush, blown down trees or large area of loose rock.

Resolution

Though maps are not perfect there are things the hiker can do to lessen the issue with maps.  Here are some suggestions:

  • Review trail guides of area to be visited.

  • Visit with other hikers that have been to the same area earlier.

  • Visit  with government agency officials  such as:

    • Forest Service Backcountry Rangers
    • Fish and Game law enforcement officials.
    • Biologists
    • Search and Rescue organizations  in the county to be visited
    • National Park Rangers


The reference for this post is Basic Land Navigation produced by the National Wildfire Coordinating Group (NWCG.)  This is a straight forward document that covers the essential elements of land navigation: it is a good introduction and the source for this post. This is a free publication.  Down load it here:  http://www.nwcg.gov/sites/default/files/products/pms475.pdf. 



Saturday, October 10, 2015

Stay On The Trail

Sectionhiker.com has a solid post about not going off trail and the damage off trail travel can do.

Have you ever seen someone trampling rare lichens above tree  line by hiking outside designated trails? Camping illegally on an open summit? Cutting down krumholz to fuel a fire? Carving their initials into a shelter? Building a new fire ring? Washing their dishes with soap in a wilderness pond? Knocking over rock cairns? Breaking live tree branches near a campsite for a fire? Digging a trench around their tent to drain rain? Leaving toilet paper on top of the ground? "



Sectionhiker.com has lots of good discussion topics with this post.

Friday, October 9, 2015

Stove Efficiency

Hiking Jim at Adventures in Stoving has a fine post to evaluate if a stove is operating efficiently.  He also has some suggestions to setup a stove for peak performance.





Thursday, October 8, 2015

Understanding 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.”


 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.

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 www.magnetic-declination.com 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.