Map, Compass & GPS

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

Saturday, March 17, 2018

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

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.

Friday, March 16, 2018

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

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:

Monday, March 12, 2018

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.

Sunday, March 11, 2018

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.

Saturday, March 10, 2018

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. 

Friday, February 16, 2018

That Old Compass

Grandfather’s compass from decades ago may no longer be the best selection for the hiker.  The image below is of a compass made between 1910-1920.  Though the dial is fairly detailed, the accuracy may be reduced due to the polarity of the magnetic needle. 

 In general terms, the polarity is how the magnetic needle will react to the earth’s magnetic field.  Over a period of almost 100 years, the compass’ magnetic needle may not move in relation to magnetic north as it did when new; that could mean the differences of several degrees.  

To prove this point take a new baseplate compass and compare the two (do not hold them near each other.)  A navigator can also compare it a new compass or a location where a street or trail is known to run true north.

My recommendation then is to leave the old antique compass in a place of honor at home.  It is time to consider buying a new compass.

Monday, February 12, 2018

Magnetic Compass Accuracy

Navigating with a magnetic compass is a skill that takes study and practice.
When plotting the hiker’s position on a map the objective is to have three lines of bearing intersect just like in the image below; this is a position fix.  That is “pin point” accuracy. This is hard to do with a magnetic compass and may not be achievable.

Blake Miller/Outdoor Quest Image
Many factors impact accuracy.  Some the hiker will have no control over.  
These include:

  1. Visual acuity (e.g., how well the hiker can see.)
  2. Polarity of the compass’ magnetic needle – does it point in the right direction? Polarity may change over time such that the magnetic needle may no longer work accurately.
  3. Smooth movement of the magnetic needle.
  4. Alignment of the compass dial to the compass housing.
  5. Local attraction – Similar to declination, local attraction is magnetic interference unique to a specific location.  It may be caused by buried metal objects or an unusually high concentration of iron or nickel in the ground.
  6. Lack of distant objects to sight on.
  7. Weather (e.g., Fog, clouds, and smoke.)
  8. Terrain may hide the objects that the hiker wants to sight with the compass.
The hiker does have control over the following.

  1. Purchasing a quality compass such as the Silva Ranger.
  2. Correctly adjusting for declination.
  3. Staying away from iron and steel objects such as a car, high tension power lines and a hunting rifle.
  4. Practiced sighting techniques.
  5. Practiced with the procedures of plotting the various lines of bearing.

Blake Miller/Outdoor Quest Image
 The image above closely represents what the hiker will have to deal with and accept.  The crossed lines of bearing provide a rough approximation of a position plotted on the map.

Terrain Association will further "dial in" the hiker's backcountry position.

Blake Miller/Outdoor Quest Image

The image above represents the error of the plotted lines of bearing.  Notice that the lines of bearing have poor angular separation. But by using terrain association the hiker might be able to refine the position fix.  If the hiker is near the river and on the on the river's east side then the position close the road  will better define location.

Navigation is not hard but it does take practice; it is a perishable skill.

When in the wilderness compare both map and compass with a GPS when possible.  Hiking companions should compare their work too.

Read other compass related posts:

     Buying a Magnetic Compass


A solid reference is June Fleming's Staying Found and Bjorn Hjellstrom's Be Expert With Map and Compass.