Find Your Way – True Grid

A series of articles dedicated to the lost art of land navigation and map reading

By H-Minus

I am a big fan of old westerns. John Wayne and Clint Eastwood were the quintessential cowboys. As a kid, I would imagine being on horseback in the wilderness. Me and the Duke gunning down a bad guy, wanted for some unspeakable crime… I would spend Saturday afternoons watching a drunken, U.S. Marshal and his Texas Ranger sidekick tracking the murderer of a young woman’s father. Or a Sunday Spaghetti Western, with the trio: Clint , Lee and Eli (AKA The Good, The Bad ans The Ugly) attempt to find stolen Confederate gold. Something always bothered me about those movies… How did these guys know where to go?… There were no roads, at least not in the movies.. So how did they know what direction to travel and how did they know how to get back home? There are some people who have a great sense of direction… I am not one of them… Even with a map and a compass, I have a difficult time getting from point “A” to point “B”. Some of us not as directionally superior as the hero’s of those old westerns. We need help! The last article discussed the “Five major” and “Three minor” terrain features associated with a map. We also touched on “Grid North” versus “Magnetic North”. This article will discuss how to establish a grid coordinate as it relates to map reading. Maps typically have one of three ways to establish a location: Latitude and Longitude Coordinates:

The geographic latitude of a point on the Earth’s surface is the angle between the equatorial plane and a line that passes through that point and is normal to the surface of a reference ellipsoid which approximates the shape of the Earth. The North Pole is 90° N; the South Pole is 90° S. The 0° parallel of latitude is designated the equator, the fundamental plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres.

The Longitude of a point on the Earth’s surface is the angle east or west from a reference meridian to another meridian that passes through that point. Latitude and Longitude is displayed in degrees, minutes, and seconds.  To be perfectly honest with you, I know very little about longitude and latitude.

Example:

Universal Transverse Mercator (UTM): The UTM system is a geographic coordinate grid-based method of identifying locations on the surface of the Earth. A position on the Earth is referenced in the UTM system by the UTM zone, and the easting and northing coordinate pair. The easting is the projected distance of the position eastward from the central meridian, while the northing is the projected distance of the point north from the equator (in the northern hemisphere). Eastings and northings are measured in meters. When interpreting a UTM grid you will read right (east) and up (north).

Example:

Military Grid Reference System (MGRS): This is the standard reference for the US military and NATO. It is also the one that I am most familiar. Unfortunately, USGS maps are not marked with MGRS. MGRS is derived from the UTM (Universal Transverse Mercator) grid system, but has a different labeling as that used by UTM. A MGRS consists of three parts.

1. A grid zone designator, GZD.  These are zones, numbered 1–60 and are intersected by latitude bands that are lettered.The intersection of a UTM zone and a latitude band is called a grid zone, whose designation in MGRS is formed by the zone number (one or two digits – the number for zones 1 to 9 is just a single digit, followed by the latitude band letter. This same notation is used in both UTM and MGRS. An example of a grid zone designator migh would be: “1Q” or 2”N”.
2. 100,000-meter square identification. This is a lettered method of identifying a 100,000-meter square area of the earth. This is what most drunts pay attention to when goingoff map. The 100,000 – meter swuare identifyer, lets you know what the next map sheet will be. It is identified by letters. An example may be “FJ” or “AL”.
3. The third part of an MGRS coordinate is the numerical location within the 100,000 meter square, indicated by numbers up to a 10 digit cordinate. A ten digit cordinate will give you a potential accuracy of up to 1 meter. The fewer digits, the less the accuracy. In the case of a 10 digit cordinate, The first five digits represent the easting in meters . The second five digits would represent the northing part of the cordinate.

Example:

We will focus on UTM grid zone designators. Simply, because it is what 99 percent of us will encounter with maps originating from the USGS. You may remember from the last article that I spoke of maps that may not have grid lines marked. If you find that your map does not have grids, you can mark them with a straight edge, pencil, and steady hand. One thing to remember when reading a grid, is to always read the numbers from left to right and then up.

Example:

If you notice the helicopter on this map, you will see it lies within a square or grid on this map. This grid is represented by two coordinates, or sets of numbers. One set of numbers goes from left to right as seen at the top of the image. The other goes from the bottom to the top as seen on the left side of the image. These represent the northerly and easterly grid lines as discussed earlier. You will see the number 17 3 73 000 represents the easterly grid line for the helicopter. The three zeros at the end of this grid refer to 100 meter markings within that grid or box. Since we are not sure where the helicopter lies within those 100 meter boxes, we can leave the zeros off for now. We will get to those numbers as soon as we determine what grid square our helicopter lies in. So, we know that the helicopter is within the 17 3 73 easterly part of the grid, now lets determine what the northerly grid is. Looking at the left side of the map, you will see a series of numbers going up in a northerly direction. This is the second half of your grid. In this case the helicopter lies in the 39 47 grid location.

If you put the two grid coordinates together you would have this:

17 3 73 E

39 47 W

You now have a grid location with 1000 meter accuracy, or as they say in the military “one klick”. A Klick is equal to a kilometer. Being the high speed land navers that we are, we want better accuracy than one klick. That is where our cool UTM grid tool comes in handy.

This clear plastic measuring device will help us determine a grid coordinate to at least 100 meters. You can even get accuracy to 50 meters or less by simply making an accurate guess to points falling within the little 100 meter blocks. Once you determine the grid square coordinates, you simply duplicate the routine using the grid tool. Remember to read right and then up.

RIGHT

THEN UP

GRID

17 3 73 650 E

39 47 400 N

Based on our calculations, we now have a grid location for the helicopter with an accuracy of at least 100 meters. It is more like 50 meters given the fact that our easterly part of the grid ends with the number 50. That pretty much covers the basics of obtaining a grid coordinate. For those of you who like to practice, there is a fun way to incorporate this into a cool hide and seek game. Find an easily obtainable location on a map, perhaps near a known road intersection. Hide a geocache near the intersection and give the grid coordinate to friends or family. Have them do the same for you. Use your new found map reading skills to find the cache and recover the items. As you get more skilled, look for local Geocaching clubs and find more difficult caches. I still wonder how cowboys made it around the wilderness without these tools. Were they so geographically inclined, they didn’t “need no stinkin maps?” Or was the map and compass a dirty little secret kept in saddle bags of cowboys everywhere? Well all cowboys except for Big bad John and Dirty Harry.

Keep your powder dry.

Continued from Introduction To Maps:

The Grid-Magnetic angle (or G-M angle) value is the difference between grid north and magnetic north. It is an arc, measured in degrees between the grid north and magnetic north lines. This value is measured in fractions of degrees, with mil equivalents shown to the nearest 10 mils. The G-M angle is important to land navigation because azimuths between map and ground should be adjusted to compensate for this difference. If not, you may be off by hundreds of meters before you get to where you are going. We will get more in depth on this on this in a future article. Terrain features of a map can be difficult to understand when looking at it from a two-dimensional perspective. The best way to describe the terrain features indicated on topographical maps is to approach it the way I was taught. Features were broken down into five major and three minor terrain features. The five major terrain features are: Hill, Ridge, Valley, Saddle, and Depression. The three minor terrain features are: Draw, Spur and Cliff. The best visual representation for these features is to get your map and compare the feature on the map to the actual land mass.  For now, let’s look at some army training aids. Five major terrain features Hill: A hill represents a point of high ground with sloping features going downward. You can also observe elevation markings on the contour lines indicating the hills sloping nature. Valley– A valley is a semi-flat piece of ground bordered on the sides by higher ground. A valley may contain a stream. The contour lines indicating a valley are U-shaped and sometimes will parallel a stream. Ridge- A ridge is a sloping line of high ground. Contour lines forming a ridge tend to be U or V-shaped. The closed end of the contour line points away from high ground. I like to remember this when trying to determine if I am looking at a ridge or valley… “valley toward,” “ridge away.” That means the U or V is going toward the high ground on a valley and away from high ground on a ridge. Saddle. A saddle is a dip between two areas of higher ground. A saddle is typically found between two hilltops. It can also be a dip along a ridge line. If you are standing in a saddle, you will see high ground in two opposite directions and lower ground in the other two directions. Depression. A depression is a low point in the ground. A good example of a depression would be a quarry. I depression is pretty much a hole in the ground.  On your map, a depression will show closed contour lines with tick marks pointing toward low ground.

Three minor terrain features

Draw. A draw is kind of like a small version of a valley. The exception being that in a draw, there is little or no level ground. You will likely find the draw a difficult feature to traverse. If you are standing in a draw, the ground slopes upward in three directions and downward in the other direction. A draw could be considered as the initial formation of a valley. The contour lines depicting a draw are U-shaped or V-shaped, pointing toward high ground. Spur. A spur is a short, downward sloping line of higher ground. You will typically find a draw formation protruding from the side of a ridge line. You may also find two parallel streams flowing down the side of a ridge. These streams will often form the spur. The ground sloped down in three directions.  Cliff. A cliff is self explanatory. I am sure we all know one when we see it. When viewed on a topographical map, the contour lines will come together into one contour line; this last contour line has tick marks pointing toward low ground. Cliffs are also shown by contour lines very close together and, in some instances, touching each other. Remember each of these contour lines represent an elevation. The closer the lines are together, the more dramatic the slope. We can go on for hours on the intricacies of maps and map reading. While writing this article, a flood of information started coming back to me from the old days. I have only touched on a very lengthy subject. If you are new to land navigation and want to know more, I would suggest you start by purchasing a USGS map of a location near you. You can pick them up at nearly all camping and hiking stores. They will also sell some of the tools needed in conjunction with your new map.

Tools for land navigation

A good compass should have at least:

• A clear base plate- To see underneath the compass.
• A rotating bezel, marked with 360 degrees in 2 degree increments.
• Meridian lines- For map use.
• Declination Adjustment and arrow- to correct for the difference between magnetic and true north

A protractor – UTM ruler:

• Your protractor will need to work with 1:24,000 , 1:25,000 and 1:50,000 scale maps
• It should also include a 360 degree compass rose for computing direction.
• The cost is usually less than five dollars, so buying an extra is advisable.

Examples of protractors: If you have or plan to purchase the army protractor keep in mind, it will only work with military scale maps. 1:100,000 – 1:50,000 – 1:25,000. Your USGS maps will have a different scale and coordinate scale part of the protractor will not work. The military protractor is known as GTA 5-2-12. This concludes the first article in our series. I must add that some of the methods and tools described are simply my way of doing business. You may have or develop your own tools and tricks. That is what makes land navigation so exciting. If your way works, do it and be proud. In fact, if you have a better way of doing something, share it with the rest of us. These skills can save you life in an emergency. Keep your GPS handy, but know how to get by without it. Technology is a wonderful tool and it gives us so much convenience and efficiency, but we can also become too dependant on it. In writing this article, evidence of our fast food society is in the very words I type. Technology allowed me to write this article without once consulting a dictionary or thesaurus. Believe me, my spelling and grammar have suffered from not picking up that dictionary. Spell check is the devil. Please check back for the next Find Your Way series of articles where learn how to establish grid coordinates and convert an azimuth. Thanks and see you again soon, H-Minus

A series of articles dedicated to the lost art of land navigation and map reading

Article 1

Introduction to maps

By H-Minus

We live in a fast food society.

I’ll bet you are wondering why I would start an article on maps and map reading with such a statement.  The fact is, the term “fast food society” refers to the automated aspect of almost everything we do. This digital age we live in has made nearly everything instantly available.  Smart phones bring the world to us.  Email can send a message across the ocean in an instant.  You no longer hear the voice of your significant other read from a map in the passenger seat of your car. It has been replaced by a pleasant British voice, or if you prefer American, saying, “in one half mile, turn left……. turn left.” Don’t get me wrong, I love the fact that things are so much easier. When it comes to land navigation, I like having my GPS.  I also like the idea that should my batteries go dead, I can find my way home without it. I was taught land navigation back in 1983.  I received the army version of land navigation training at Ft. Benning, Georgia. It was just enough to get me lost. I didn’t learn land navigation until I finished Jump School and was assigned to the 1^st 505 Parachute Infantry regiment.  Like other new troops, I was taken into the fold of the senior NCOs, all of whom were Vietnam veterans.  They were some of the best teachers I have ever met. Don’t get me wrong, I can still get lost with the best of them, but I have a better chance than most of finding my way home. Cartography, or mapmaking goes back thousands of years, some say as much as 8000 years ago.  A map is simply a tool to help describe and navigate an area. It can be land, sea, air and even space. Let’s stick to land.  There are several types of land maps in use today. We are going to focus on topographical maps and the tools used with these maps. A topographical map is a two-dimensional representation of three-dimensional land surfaces. These maps use contour lines to show changes in elevation on a map. Contour lines have a numeric representation that refers to distance in elevation.

Most of the topographical maps in use today are prepared by the USGS. These maps show much more than contour lines. They contain symbols that represent buildings, airports, vegetation, cemeteries, campgrounds and much more. Different types of lines represent roads, rivers, and boundaries. In fact, there are so many symbols and lines, one can’t remember what they are without help. That is where the map legend comes in handy.

Some of the maps developed by the USGS have grid lines. Some have only grid “tic marks”. If your map has only tic marks, you can draw the lines in with a straight edge.  Each of grid is marked with numbers going from left to right and up. These marks are used to determine locations on a map and convert the location to a series of numbers that represent a grid location.  We will discuss how to use grids in another series.

Each topographical map will include a reference to three types of north. One is called “Grid North.” The second is called “True North” and the third is called “Magnetic North.” Grid North – The direction of a grid line which is parallel to the central meridian on a map. True North – The direction of a meridian of longitude that converges on the North Pole. This is just another way of saying that True North describes a direct line to the North Pole and the Earth’s spin axis. Magnetic North – The direction indicated by a magnetic compass. This is the north that your compass will seek. The Grid-Magnetic angle (or G-M angle) value is the difference between grid north and magnetic north. It is an arc, measured in degrees between the grid north and magnetic north lines. This value is measured in fractions of degrees, with mil equivalents shown to the nearest 10 mils. The G-M angle is important to land navigation because azimuths between map and ground should be adjusted to compensate for this difference. If not, you may be off by hundreds of meters before you get to where you are going. We will get more in depth on this on this in a future article.