Map, Compass and GPS

MC-2 Suunto Sighting Compass

Whenever you head out into the woods it is essential that you bring a map and compass with you. Know how to read your map by being able to interpret the symbols and contour lines.


Maps usually have a legend which help you to interpret the symbols. Information is also given about the scale of the map as well as the magnetic declination of the area.


Know how to use your compass as well!

I will not teach you here how to do these things, however I will help you by providing some information and by providing links to other sites where you can learn.


There are many different types of compasses on the market. Some big names are Suunto, Silva and Brunton. You can purchase these quality compasses at the many different sporting goods stores in your area. There are different compasses for different purposes, select one accordingly. Avoid electronic compasses for backcountry use, and go for a baseplate compass instead.

Compass reading while using a map can be interesting for several reasons. For one thing you can 'see' the land all around you with the map properly oriented. It is as though you are standing in the middle of the map, and that you know where all the natural features are with respect to your current position, even if you cannot physically see them. An example is knowing that a lake lies due north from your position, even if you do not physically see it with your eyes, but it is there. A map brings it all to you, lakes, streams, hills and mountains etc.


Can you see how this is a major reason for having a map and compass should there be an emergency?


Compasses must have a needle that is balanced for the hemisphere in which you intend to use it. Suunto has a two zone system, where a compass so equipped can operate in the Northern Hemisphere, as well as south of the equator, but only to a point. There is a compass with a global needle, where the needle is balanced for both hemispheres. Magnetic inclination or magnetic dip, is responsible for causing a magnetic needle to 'dip', and if this inclination is too great for the compass, the needle will get stuck and cease to function in that area.


Contrary to popular belief, a compass needle does not point to the magnetic pole, but aligns itself with the horizontal H-Component of the magnetic field where the compass is being utilized. Saying that the needle points to magnetic north would be sufficiently accurate, but not to the magnetic pole. Isogonic charts are utilized to show the magnetic lines of force operative over the globe. These charts can also help you to determine the magnetic declination for the area you live, and the area you intend to use your compass. Every 5 years the chart is updated to maintain the accuracy of the data. Have a look here to see your location in latitude and longitude as well as the magnetic declination for your area.

View Through a Sighting Compass

Backcountry maps are called topographic maps, or topo maps in short. These maps give a 3D representation of the terrain on a 2D sheet of material which is your map.


Planimetric maps (like road maps) are maps that are 2D only, in other words they do not have contour lines to show you the elevations for the terrain. There are other differences as well in order to reflect their intended purpose.


This is not a suitable backcountry map, however, it might be useful none the less under certain conditions.

Use a topo map which is designed for backcountry use. Topographic maps also may have Latitude/Longitude lines as well as UTM (Universal Transverse Mercator) grid lines superimposed on the maps.


For backcountry use, a good scale for a map here in Canada is 1:25000, or 1:50000 which may be preferable. Any smaller such as 1:250000 and you will not have many details at your disposal, whereas if the scale is larger, you'll have more details than necessary, and will need more maps to cover the area, because one physical map will not be large enough.


I am not asking you to become a geologist here, but be aware that in some terrain there may be magnetic properties in the landscape that may affect the precision of your compass. Be careful when you place your map on the ground with your compass to orient the map, for there might be the possibility of errors that may occur as well. Check with the features in the landscape to act as a confirmation of what your compass is telling you.


It is recommended to carry two quality compasses, not just for the sake of having a backup, but also for the psychological aspect. Under stress, a person might question the compass reading and disbelieve what it is telling them. They'll rationalize that their sense of direction is correct and the compass is 'off'. With another compass (not some cheap piece of junk) you can verify the initial readings, and if they concur, then you have confirmed that the compass reading was good after-all and that your sense of direction is what was 'off' :) Have a look at Elements of Survival for more information on survival psychology.


A GPS which stands for Global Positioning System, consists of a constellation of 24 active satellites with 3 in reserve in case of failure.


The United States Department of Defense has control over them. These satellites permit you to know your coordinates anywhere on the earth when you use a GPS receiver.


Many models are available with various functionalities. There are some that are designed for use in a vehicle that guide you along as you drive, and some are portable which are very useful for backpacking and for other times where a small portable receiver is welcomed.


However map reading and using a compass is still an essential backcountry skill. If you rely solely on a GPS receiver for traveling, and run out of batteries, or the unit gets damaged somehow, you'll potentially be in big trouble. In effect you'll be lost. If you remain on established trails it isn't normally a problem, but have a map and compass available should you need one for some reason or other. You never know when something might happen. People get lost every year for various reasons out in the woods, including experienced outdoorsman such as hunters.


Another thing to consider about GPS receivers, is that there are times where it may be difficult or even impossible of receiving the satellites signals, due to bad weather, heavy canopy (tree cover) and terrain such as if you are in a canyon. A map and compass is needed in these cases if you are to navigate with confidence. 


Also as mentioned above, that the United Stated Department of Defense has control over the satellites. There is a 'civilian' band and a military band of frequencies that are used to communicate ephemeris data to the GPS receivers. If another terrorist attack happened, the U.S. D.O.D. can turn off the 'civilian' band or scramble it over a selected area, to prevent an enemy from utilizing GPS technology in their terrorist activities against the United States. What this means is that should this happen, the person who relies solely upon GPS technology for backcountry use will have a big problem. The GPS would no longer be receiving a signal, or if it does, the data will be misleading. Once again, map reading and using a compass is still an essential backcountry skill.


Keep in mind that it wouldn't hurt to have physical maps of the areas you travel by car in your glove compartment or car kit, perhaps even an Atlas for a greater coverage, or have extra maps if necessary. This is just in case something happens, and that your on board GPS in your vehicle ceases to be reliable. At least you'll have a backup. Do the same for your emergency kits as well.


A GPS is a very useful and helpful instrument, but it is not reliable enough for backcountry use for the above reasons, and there are others. It should be used for taking position fixes and course corrections. Use your map and compass for navigation, or if you insist on using a GPS, at least have a map and compass as a backup in your possession with the skills to use them.


If you utilize your GPS in conjunction with a map, be certain to use the correct datum or you will not get accurate information for navigating. WGS-84 is often used in North America. There are many others depending on the area of the world you may be in.


Here are some links to aid you in your studies on maps, compasses and GPS receivers.

1. Compass Dude

2. The Atlas of Canada

3. Global Positioning System - Official U.S. Government information about the Global Positioning System (GPS) and related topics

4. Survival Topics

5. DeAnza College - GPS is not infallible.

Resources

Backpacking Navigation #2 - Map, Compass & GPS - CleverHiker.com

At 5:50 in the video he points out the lines on the map and says they point to True North, the North Pole. This is inaccurate. These are Grid Lines, and even though they point in a northerly direction, they do not point to True North, but to Grid North.

Parallel lines cannot point/converge to a single specific location such as the North Pole. True North is the point where the lines of Longitude meet.

The orienteering lines inside the compass housing still must be aligned with the grid lines on the map in this case, and then you proceed to 'box' the red end of the needle (North) between the red lines with the red arrow (orienteering arrow) in the compass housing. Have a look Compass Dude for more information.

Sometimes it is called putting Red Fred in the Shed or Boxing the Needle among other things. Be certain to do this right or you will be 180 degrees off! It is a mistake that beginners often make.