Re-Post from MDT
General: a map is a birds eye view representation of the ground. It uses symbols, shapes, colors and contours to show what is on the ground. You should familiarize yourself with map markings so that you can read the map. Below is an Ordnance Survey (UK) map of the Brecon Beacons as an example. A map has various markings around the edge such as a key and scale, which will help you read the map. If you are looking for maps of your area, you should look at mytopo.com where you can get custom maps. If you are ordering maps you want them in either 1;50,000 or 1:25,000 scale. These are best for general military/navigation purposes. At MVT you will use a 1:25,000 scale map. You should order them in MGRS with visible grid lines. This will allow you to use grid references. Do not order them in lat/long.
HERE is a link to a page with some land nav presentations. There is one on basic map reading. Read them along with this post – there is almost too much information there, and I don’t want you to become confused. Use the presentations to get additional familiarity/practice.
Scale/Grid: a 1:25,000 map means one unit on the map (which size unit is irrelevant) equals 25:000 units on the ground. An MGRS map will have a series of grid lines on it. The eastings are the vertical lines and are numbered from left to right, along the bottom, top and at various points within the map. The northings are the horizontal lines and they are numbered from bottom to top, along the left, right and in the middle of the map as appropriate. You can see grid lines marked on the map above, eastings going from 97 through 00 to 05 (numbers are in the middle of the map because we can’t see the edges of this particular map excerpt, but it makes no difference. Imagine if your map was folded). The northings are numbered 18 thru 22, again you can see them in the middle of the map, in blue writing. These numbers are written on the blue grid lines.
Each grid square box is 1 kilometer, which is 1000 meters. On a 1:50,000 map the grid squares will just be smaller than on a 1:25,000 map, because everything is represented twice as large on a 1:25,000 map, which makes it better for detailed navigation.
Grid References: Now that we have these 1000 x 1000 meter boxes, it allows us to specify a point on the ground using grid references. We always read the eastings first, then the northings. You can remember this by “along the corridor, then up the stairs.” So we read the numbers that run left to right, then we read the numbers that run bottom to top. The graphic below shows this.
A ‘four figure’ grid reference simply gives us a 1 km square. Remember that a grid reference gives you the bottom left corner of any square, not the center. On the diagram above, the very bottom left corner of it has the four figure grid reference of 1642. That is 16 on the easting scale (along the corridor) and 42 on the northing scale (up the stairs). That gives us the bottom left corner of that 1 km box. The grid square at the top right of the diagram is referenced by 2046. 20 along the easting scale, 46 on the northing.
Look on the Brecon Beacons map above. You will find Pen-y-Fan center top of the map. Look at the blue grid line numbers. You will see that the 4 figure grid for Pen-y-Fan is 0121. 01 eastings, 21 northings. Note that this does not give the exact location of Pen-y-Fan, it just references the bottom left corner of the grid square within which Pen-y-Fan lies.
A ‘six figure’ grid reference gives us the lower left corner of a 100 meter box. The grid square is 1000 meter x 1000 meters. What we are doing is subdividing the sides of the grid square into 10 x 100 meter increments. This is not physically gridded, so you have to do it by eye or use a tool on your protractor/compass (more on that in a bit). In the diagram below, you can see our original 1 km square further divided into 100 x 100 meter boxes, with what is in reality an imaginary scale of 1-10 along the bottom (eastings) and side(northings). The 4 figure grid for this grid square represented is 1844.
Looking at the diagram above, you can see the red circle. This highlights a 100 x 100 meter area. To give the 6 figure grid of this area, we first go along the corridor to 5 (eastings), then up the stairs to 3 (northings). This gives us the bottom left corner of the box highlighted in red.
The four figure grid was 1844.
The 6 figure grid is 18 5 44 3. Or 185443.
You have to figure out that it is a 6 figure grid and the first 3 numbers are eastings, the second three are nothings.
Without the aid of GPS, a 6 figure grid is really the best we can do. It gives you a 100 meter area.
In the diagram above, there is also a grey box. The 6 figure grid of the grey box is 187448.
An ‘8 figure’ grid reference gives you the bottom left corner of a 10 meter box. This means we further subdivide our 100 meter box into 10 further 10 meter sub-boxes. As shown in the diagram above, if we wanted to get more exact where within our red highlighted 6 figure grid box we were, we would sub divide it. Using compass/protractor analog skills, it is really nothing more than an estimate. We might say 1854 4436, written as 18544436. The initial 4 is an easting, saying 40 meters along the 100 meter box, the secodn 6 is a northing saying 60 meters up inside the box. If you are given an 8 figure grid during land nav, it allows you to dial in more specifically to where the check point may be.
Can we go to 10 figures? Of course, but there is no use for it in this application. That is a 1 meter location.
Looking back at the map of Brecon above , we can see that the 6 figure grid for the top of Pen-y-Fan is 012216 – it is in grid square 01 21. It is 2/10th (200 meters) east and 6/10th (600 meters) north of the bottom corner of that grid square.
The map below shows a 6 figure grid 193467. Note in this case the eastings are read along the top of the map. It doesn’t matter.
Topography: other than symbols and colors representing various things on maps, such as roads, built up areas, woods and water courses, one of the main features on maps is terrain. A map is a 2D representation, and terrain relief is described using contour lines. Contour lines are usually brown. They are lines that join points of equal height above a reference height, usually sea level. You need to check out the key on a map to figure out what height separation each contour line is, and what unit of measure i.e. feet, meters etc. There is an index contour which is darker than the intermediate contours. Once important thing to remember is that there may be features between contour lines that do not quite break the height of the contour lines above and below, and therefore are not shown on your map – this could be anything such as small hillocks etc.
When looking at contours you have to imagine the contours and how the ground will look. The contours will define terrain shapes and also steepness – the closer the contours are together, the steeper the slope. There are a number of terrain features that you should be familiar with. Once you can use the contours to visualize the ground, you are on the way to being able to navigate using terrain association.
The graphic below shows how contours are used to build the shape of a terrain feature:
The diagram below uses numbered examples of the terrain features you should be able to recognize
The map below uses shading to bring out the terrain features – this is how you should imagine the terrain when you look at contours on a map:
Below: Spur (draw) Make a fist, your knuckles/fingers are the spurs, the gaps between your finger are the draws:
Below: Cliff (not shown by contours, but by hatching – contours would be too tight together):
With contours, a good tip is to use the water courses to help the terrain pop out at you. Streams will run down the low ground – in draws, not on spurs, so it helps to make sure you don’t invert the terrain in your mind. Also, where contours are marked with heights, the numbers will read so the top of the number is pointing towards the higher ground.
Grid Lines: An MGRS map is overlaid with a grid pattern. We already talked about this with grid references. The grid pattern is just used for the maps. The eastings run north-south and the northings run east -west. These are not the same as lines of latitude and longitude. In effect, it is a reference grid for taking grid references. This means that there are 3 norths as far as our maps go: True north, which is pointing to where the actual north pole is. Grid north is where the grid lines point to at the top of the map. Magnetic north is where our compass needle points to, which is not the north pole. Magnetic north also moves in increments as the magnetic pole shifts.
True north does not matter. The only ones that matter are grid north and magnetic north. Magnetic north only matters because we use a magnetic compass to navigate with.
Grid Magnetic Angle (GMA, or declination):
Because there is a difference in location of where our grid north is, and where magnetic north is, there is a problem with any kind of direction between the two. If I take direction on the map (also known as an azimuth, or bearing) and want to put it on my compass so I can walk it on the ground, the problem is that my compass points to a different north. Depending where you are in the world, the GMA varies. However, once you have worked it out, you know what it is. Think of it like an offset: if I take a grid bearing, I need to offset it to use with my compass. If I take a bearing with my compass, I have to offset it to use it and plot it on the map.
The GMA can be east or west of grid north depending where your map is. It is an angle off offset. The diagram below shows a GMA (also known as declination, or magnetic variation). You will find a similar diagram on your map:
In this case, the magnetic error between grid north and magnetic north is east. This diagram has a 1960 GMA of 9.5 degrees. What this diagram would also need would be a rate of change – it would normally say, GMA 9.5 degres in 1960, changing by (for example) 0.5 degrees east every year. You would do the math and work out the current GMA! However, here the GMA (declination) is 9.5 degrees east. Now, with a basic standard of accuracy we can only really work in 5 degree increments with our compass and for practical navigation, so just round this to 10 degrees east.
What this means is that if I took a grid bearing from my map, and didn’t apply GMA to the compass bearing, I would be missing my destination by 10 degrees. You can have GMA of 30 degrees in some places, the more north you go! Be careful where you are in the world. However, once you know it for your area, you are set. In Romney it is currently 9 degrees west. So 10 degrees west for practical purposes.
So what do we do? Remember this: Error East, Compass Least. Error West, Compass Best.
So, with a west error as in Romney, the compass bearing will always be more than the grid bearing. It is 10 degress west, so if I take a bearing on my map of 270 degrees, in order to walk that with my compass, I have to add 10 degrees to make it 280 degrees. Think of it like: the compass is off to the west by 10 degrees, because it is pointing at magnetic north. In order to align it with the grid north, I have to add that 10 degrees. If the error is east, to align it I have to take the error off.
It’s like holdover with your rifle, or aiming off for wind.
If I am going from my compass to my map, with a west error I have to subtract it. Let’s say I took a compass bearing to an object and wanted to plot that on my map. If the compass said 320 degrees, then with a 10 west GMA I would subtract it going to my map, and plot 310 degrees on my map.
This isn’t much for short distances, but 1 degree is 1 meter at 1000 meters, so as you go further and with a larger declination (GMA), you will be off by more and more. You will miss the checkpoint. Unless you are also using terrain association!
Compass: The military will have you use a lensatic compass. This is great for intersections, resections, fire missions, dead reckoning navigation etc. The problem is that there is no interface between your compass and your map. The interface is provided by a separate protractor. So for land navigation, patrolling etc, ditch the lensatic in favor of a Silva/Suunto style orienteering compass. Below: Silva Compass.
This type of compass will lay directly on the map and incorporates a compass and a protractor. It also incorporates (not all models do) a 1:25000 and 1:50,000 grid reference tool. You just slide it along the grid square and it tells you what the grid reference is.
On the diagram below, you see a Silva compass laid on a map in order to take a bearing. The long sides of the compass/the directionof travel arrow are/is laid along the desired direction of travel. You can see there are two black dots marked at the top side of the compass, and the desired direction of travel is between the two. You then rotate the bezel of the compass, which is marked as 360 degrees, so that the red internal arrow/north pointer is aligned with the grid lines (green arrow on the diagram). Make sure it is aligned pointing north on the map, not south, or you will walk opposite! It is at this point that you would take account of the GMA, in the case of Romney by adding 10 degrees, so rotate the bezel off by 10 degrees. Looking at the compass in the diagram, it looks like the desired direction is just south of east, or 106 degrees (green dot on the diagram). So add 10 degrees by rotating the bezel to 116 degrees.
So now we have taken a bearing on the map, a direction we want to walk in, and made it into a magnetic bearing on our compass. Now, what you should be doing is keeping the map oriented to the ground. So that north on the map corresponds to north on the ground. This map orientation will then allow you to relate features depicted on the map, with features on the ground. So once I have taken my bearing, I can use both map and compass, or just compass. Holding one or both in front of me, I will turn around until the red needle in the compass lines up with the red arrow inside the bezel. I am holding the compass in my hand so that the direction of travel arrow points away from me. If I still have my map out, I can now orientate the map, if not done so already. Now, standing there with my compass held in front of me, I can look at the direction of travel arrow and then off into the distance where it points. I identify a point on the horizon and then I can start to walk towards it. Don’t walk staring down at your compass. Pick a series of points and walk towards them, picking another one every time one is needed.
1) Ensure your checkpoint grid reference is accurately plotted on your map.
2) Know your departure point – orient the map to the ground and know where you are.
3) Make a route assessment of the best way to get between your points.
4) Use terrain association as much as possible: avoid azimuth/pacing type navigation as much as possible.
5) Use a green/amber/red system where you make your speed early (green), as you get closer you start to get into amber where you are navigating more carefully, then get to red as you are finally looking for the check point.
6) In conjunction with the above, use ‘attack points’ where you navigate as fast as possible using terrain association, then use a known point to attack the check point. This is where you may need to use a bearing along with pacing to find the specific location. An example would be using a known track junction to attack into thick woods for a couple hundred meters using a combination of bearing/pace count.
7) Know your pace count over 100 meters when running, walking and carrying your combat load. Go 100 meters then go back, taking an average. Count when your left foot strikes the ground. Carry a pace counter to record every 100 meters as you navigate on a leg. Don’t do all your navigation like this however, use terrain association where possible.
8) Handrail or use known features like ridgelines, trails or creeks. This is navigation, not patrolling, so where allowed use trails and linear features.
9) If heading across country, use terrain features and gradient to check off features. Example: crossed first creek, crossed first road, heading uphill, crossed ridgeline, heading downhill, hit second creek – in conjunction with a bearing and pacing this will keep you from getting lost. Also, use a backstop feature where you can i.e. I’m not crossing over the main ridge etc.
10) Aim Off: if heading for a checkpoint that lies on a linear feature, you won’t know which way to turn when you get to the linear feature, such as a road, to get to the checkpoint. In this case, deliberately aim off sufficiently to one side, hit the linear feature and turn in toward the checkpoint.
11) Contouring: this is where you stay at a certain height on the side of feature and simply follow the feature around. This is efficient because you gain/lose less height.
12) Cross -Graining: this is where you take an azimuth straight across country, over ridgelines etc. A direct route but not efficient. Lots of elevation gain/loss.
13) If you can’t find your checkpoint, don’t blunder on. Go back to a known location, such as the attack point, and try again.
If there are aspects that I have not included, or questions for clarification, I will take them in comments.
Dan Morgan’s thoughts here
Why land navigation?
Posted: 12/14/2014 in Uncategorized
I’ve recently noted several comments on different blogs asking why all the emphasis on land navigation. Why not just learn your Area of Operations/Area of Interest (AO/AI) like the back of your hand, because you will most likely never venture out of it during WROL anyway. Well, Pilgrim, my best short answer is; land navigation is a valuable skill, that is easily learned and mastered with practice, over time. And like any skill, it makes you a more well-rounded and valuable asset to any team. Why do I need to become familiar with the AK/SKS/Mini-14/FN-FAL/HK systems and every sidearm/shotgun I can get my hands on since I only have an AR-15 ? You never know what you might pick up off of the battlefield.
My best long answer; it is very difficult, even for folks experienced in land nav. to navigate at night, in bad weather, with little or no illumination over broken terrain. Add to that; while humping ruck, tired and hungry. Let’s look at some scenarios.
Scenario 1: Your retreat four man R&S patrol is patrolling the ridges surrounding the outside of your AO when they are forced to deviate from their planned route by the unexpected presence of a large group of armed men. They radio in a SALUTE report to back to your group. The OPFOR group’s size, movement formation and route forces your patrol to evade into an area they are unfamiliar with during the night. Come first light, they find themselves in a heavily wooded area surrounded by low mountains. They must now determine their present location and plan a route of return to your retreat. If they can patrol to one of the mountain peaks, they can orient their map to grid north and either terrain associate or re-section their present location and then plan their route back.
Scenario 2: Your groups ability to make trips to the local barter market have been disrupted by the presence of vehicle mounted harassment/shakedown patrols by groups of local thugs that have recently escalated to include the murder and kidnapping of folks from adjacent groups. After surveilling their operation along different routes for several weeks you determine enough information about them to conduct an early morning ambush of their largest group along a road. This mission will be conducted by several groups with your providing leadership.
Without land nav skills, how will you do your leaders recon of the ambush site, as per SH 21-76 (my favorite, the 1992 version), emplace your security element with eyes-on the objective and find your way back through the release point and then back 300 meters to the ORP at 0200 in the morning, in the rain, and fog, with zero illumination? Or, if you choose to stay on the objective, and send a subordinate leader back to the ORP whereupon he must then lead the rest of the patrol back through the release point to the ambush site, how does he find his way back to the ORP and then subsequently return to the release point? If you’ve not taught him the fundamentals of night land nav he will either A; go off course trying to find the ORP and then decide to sit tight until daylight ruining the ambush opportunity or stumbles up to the ORP off the expected azimuth, whereupon the patrol fires him up and you have a blue-on-blue catastrophe. Or B; he manages to find the ORP and then leads the patrol off course to the ambush site and they stumble upon the road at a different location ruining the ambush and subjecting them to compromise by a vehicle mounted OPFOR patrol.
Scenario 3: You are asked over your pre-established radio net by the folks in a neighboring community to provide mutual assistance in order to deal with the Leroy Jenkins Gang (thanks Sam) by conducting a raid on their compound. The gang has been ravaging the general area, but has left your group alone due to the severe ass-kicking they took the first time they ventured into your AO. You are going to meet up with your neighbors in the middle of the night at a particular farm outside of your AO. They, being somewhat familiar with land navigation give you the 10 digit grid coordinate to that location. Using maps of the area outside of your AO, which your group ordered and stored well ahead of time, you must now plan a route of march, through unfamiliar territory, to your link up and after the mission is complete, in keeping with good tactics, you must have planned a different route of return to your retreat. Then you must execute that movement under cover of darkness, through heavily wooded terrain in order to mask your movement for two reasons; you do not want the gang to realize part of your force is absent from your retreat thus making it vulnerable, they have their snitches in the area you know, and you don’t want the gang to realize something is afoot making them wary. Surprise is an important combat multiplier.
So, three scenarios regarding the importance of land navigation. I apologize that they all involve combat patrols, but that’s my frame-of-reference. I’m sure with some thought you can come up with other reasons. I would suggest looking around online for land navigation sites to include the land nav primer at Max Velocity’s site. Then go out and take a land nav class or join an orienteering club for some hands-on experience.
Have fun boys and girls.
Choosing a compass
Posted: 12/16/2014 in Uncategorized
I’ve been asked by several readers which compass I use and why I chose it. My primary compass is the Suunto MC-2, my alternate compass is a Suunto A-10 and the compass in my survival kit is a little Brunton Globe. While in the Army we were trained to use the standard military lensatic compass but, during the deployments during GWOT, some SF teams were issued a version of the Suunto MC-2 with special tritium illuminated parts that most of us found to be superior to the lensatic.
Like weapons, not all compasses are of the same caliber and no one compass excels for all uses. Some are toys, some are junk and some are overkill, so depending on the terrain you are operating in and what you are doing at the time, they can get you lost and embarrassed or worse, lost and dead. If I had to bet my life on a compass, it would be either a Suunto, Cammenga or a Brunton. My primary, the MC-2 is considered an advanced nav. compass and it is pretty rugged. My secondary (backup) is an orienteering compass that is quite a bit lighter, and while it won’t take the licks the MC-2 will, it will allow me to continue the mission. The little Brunton Globe is my go-to-hell compass, it will get me home and that’s about all I can ask of it. Avoid very expensive professional compasses designed for surveyors, loggers and geologists. They are usually a little bulky, heavy and you’ll cry like a baby when you lose it or break it. Also avoid the Chi-com made Silva compasses like the plague. Yes, Silvas sold in North America are made in China. The true Silva compasses are still made in Sweden but are not imported here. I still have a Chi-com Silva Ranger someone gave to me that has the direction-of-travel arrow pointing in the wrong direction. The Suunto is made in Finland, the patron nation of orienteering, the Cammenga in Michigan and the Brunton in Wyoming. My only hands-on experience with the Bruntons, beside the little Globe, is the Army M-2 that was used by Army mortar and artillery crews and I remember it being a well-built compass. If you’ve used the virtually indestructible M-1950 military lensatic compass, you’ve probably used a Commenga. The civilian version of the M-1950 is the Commenga 3H. As far as I know, it is the only civilian compass with a tritium illumination. The use of tritium allows the compass to self-illuminate without the aid of a light that is required to charge the phosphorous in other compasses. The life of the tritium is about 10 years (true half-life of 12 years). If you feel that the lensatic compass is for you, a word of warning; there are tons of cheap Chinese knock-offs floating around. I see one or two at each land-nav class I teach. Usually, they are made of plastic, don’t have a dampened floating needle, (the needle never seems to settle down) and the parts that are supposed to be phosphorus are just green paint. Also of note; if you find a military surplus lensatic, it’s probably past the half-life of the tritium and will not illuminate properly. Check for the manufacture date on the back of the compass.
What to look for in a good compass:
The compass should have a liquid filled housing with no bubbles under the lens and a jeweled needle bearing.
The base plate should be transparent in order to view a map through, and have embossed scales relevant to the maps you will use.
The needle, orienting arrow, rotating bezel ring and orienting marks should be luminous for night use.
The bezel should have detents (or “clicks”) to hold it in place when set.
There should be an attaching point for a lanyard. This is pretty important. I usually keep my compass lanyard (a piece of gutted 550 cord) tied through the button-hole in either my top left shirt pocket or lapel, or if no button-hole when wearing a combat shirt, attach it to the suspenders on the battle belt or a plate carrier attachment point. My point is attach it to your person. Do not tie it around your neck, that’s a no-no that might come back to haunt you during a ground combatives engagement. Do not make the lanyard so long that it can reach the ground when you go down on one knee. Old war story; I had a buddy going through SF Selection with me, taking the land nav. exam when he fell onto a knee at night while moving through the woods. His lanyard was so long that when he fell, his knee fell onto his open compass, breaking out the lens and crushing the needle. He had no backup compass and failed the exam. Close your compass cover and stow it away when you’re not looking at it.
Additional items I look for:
A hinged cover with integral mirror. The cover protects the compass face, base plate and mirror from damage and, of course, keeps the mirror from flashing inadvertently. The mirror is used for the more precise land nav. functions such as section/re-section. It can also be used for applying camo, signalling, shaving, and checking for ticks in those places you can’t normally check by yourself and your Ranger Buddy probably won’t help you with. When the mirror is folded out flat, it gives the user a longer straight edge for drawing lines on the map.
Multiple map scales and rules. Something very important to consider before purchasing a compass.
Determine the scale(s) of the maps you intend to use since the scales on the compass need to match them. With the Suunto, the embossed compass scales will either be in inches (standard) with map scales of 1:24,000 and 1:62,500 for use with USGS maps printed for the United States, or for maps of virtually all other areas of the world, the compass scales required will be in centimeters and the map scales of 1:25,000 and 1:50,000. Military Grid Reference System (MGRS) maps, including those of the USA, use metric scales. I keep compasses for both type of maps.
Magnifying glass. Comes in handy for reading the fine map print, especially when you are long-in-the-tooth, like me, and the eyes start to go bad. It can also be used to start a survival fire, providing the big heat-tab-in-the-sky is shining.
An adjustable declination setting. Determine the declination for your AO, set it into the compass once, and forget it. Big time saver and one less mistake to make.
Sighting apertures and wires between the base and hinged lid.
Most compasses are hemisphere specific. A compass made for the northern hemisphere will not work in the southern hemisphere and vice-versa. You can, however, buy a special compass that will work in both.
For example: The Suunto MC-2 360/D/L/CM/IN/NH has/built-n Declination adjustment/Luminous dial/inClinometer/INch scale/works in the Northern Hemisphere. The Suunto version for both north and south hemisphere will have the letters NH/SH or G for Global. Each uses a different method of needle stabilization.
If you have any interest in land navigation and are planning a compass purchase, visit your local sporting goods/backpacking store and puts your hands on one first. Usually someone behind the counter will have some experience with one. Another good source of information is a local orienteering/hiking club.
I have updated this post to include this Youtube video that I think will help. It is very well done.
The Topographic Map – UTM Grid System
Posted: 12/18/2014 in Uncategorized
An important aspect of using a topo map is the fact that you can pin-point a location on the earth, transpose that location onto the corresponding map with fair precision and then communicate that location to others. This allows you to locate and share items such as link-up points, caches, targets, en route rally points, etc. The most efficient method is the grid reference system.
I won’t go into a detailed topo map discussion here, Max Velocity’s already done that on his site with an excellent primer. He explains how to locate a point on any 1/25,000 OR 1/50,000 topo map using the Military Grid Reference System (GMRS). If you are attending his course he has written that this is the map system he will use. He goes on to write that you can buy any USGS topo map with the GMRS grids pre-printed on your personalized map at mytopo.com. I have ordered maps from them and I highly recommend them.
For those folks who already have a stock of USGS maps that are 1/24,000 maps, have the ability to print their own maps or have compasses in 1/24,000, I will explain how simple it is to draw a grid system on your map. The following is taken directly from maptools.com:
All USGS topographic maps printed in the last 30 years or so include UTM grid tick marks, in blue, on the margin of the map. For a short time period after 1978 the USGS was printing a fine lined UTM grid on their topographic maps. They have since discontinued this practice.
Since most USGS 1:24,000 scale topographic maps do not have grid lines printed on them, you will need to draw them in by hand.
Start by finding a flat surface to work on. Use a straightedge that is long enough to draw a line across your map. Two to three feet long is a good length.
Line the straightedge up between two corresponding UTM tick marks along the neat line (the edge) of the map. Remember that UTM grid lines are not exactly North-South or East-West anywhere but in the center of a zone. This means that the grid lines will not be parallel to the neat lines.
Using a mechanical pencil or a fine pointed pen draw a line between the two tic marks. If you are using a pen, select one that has waterproof ink. In addition, you will want to use a straightedge that has the edges lifted off of the paper. This will help keep from leaving an ink smudge when you move the straightedge. High quality straight edges will often have a thin piece of cork stuck to the bottom. This helps keep the rule from slipping, and keeps the edge off of the paper. A piece of masking tape centered on the bottom of your straightedge will work also. Occasionally wipe of the edge of the straightedge to avoid any ink build up.
Gridding maps is tedious work. We all wish the USGS would go back to printing the grid on the map. But even then, we would still need to grid our existing maps. As you can see this is not the kind of thing you want to do on the hood of a truck or using a flat rock. Grid your maps before you need them in the field! In a pinch you can fold the map over on itself and use the edge of the paper as a straightedge.
A couple of items that bear repeating; the outside map margin or border is known as the “neat line” and the UTM grid tics are tiny, blue lines that extend out from the border (or neat line) on each side, top and bottom. Insure that when you draw in your lines that the UTM grid tic mark numbers match top to bottom or side to side and they are all parallel to each other. When you are finished you will have a matrix of squares filling in your map. Some of the grids along the margin might not be complete squares, until you join up adjoining map sheets with grid squares drawn on them also.
The squares you have drawn are one thousand meters across or in other words, one kilometer. Or as we said in the Army, one “click”.
Now you can use the scales on your 1/24,000 compass base to locate items up to 100 meters.
Another nifty tool I always carry in my map case is the Brooks-Range All-in-one Map Tool Pro. Google it and blow up the picture on your computer. It has every scale I’ve ever used and some I haven’t. It also has your grid reference tool for 1/24,000 maps that you just lay over your map. It also contains slope indexes along the bottom that you can lay over the contour lines on any map and it will give you the corresponding incline. It also has a compass rose in the middle surrounding the grid index. If you gut a piece of 550 cord, pierce the very center of the compass rose intersection with a needle creating a tiny hole just large enough to feed one of the 550 strands through, tie a knot on the strand on the front side of the tool, then pull the strand through the hole in the tool until the knot tightens against the front of the tool. When you are finished you can lay the tool on the map, north pointing to the top of the map, with the center knot over your present location, turn the tool to align the map tool edges or grid lines with the grid lines you have drawn on your map, then pull the strand around until it intersects your target on the map. You can then read the direction or azimuth in degrees to your target off the compass rose on your tool. No need to draw lines on your map or to even lay your compass on the map. Now set your azimuth into your compass, keeping in mind the declination offset (unless it is built into your compass) then move out and draw fire.
Dead Reckoning versus Terrain Association
Posted: 12/24/2014 in Uncategorized
When moving from A to B, what land nav. movement method should you use and why?
Dead reckoning (actually Deductive reckoning) is the method normally used when moving in very low light conditions such as heavy rain, fog, snow or at night. Also when moving through very thick vegetation, such as thick forest or dense jungle, or an area with very few recognizable terrain features, such as prairie or very flat desert. It would also be used if moving from an attack point very near an objective to ensure you don’t miss it.
Dead reckoning involves first determining, on your map, your current location, then the distance and azimuth (bearing) to your objective. The azimuth is dialed into your compass, rotate your body until your north seeking arrow is aligned (RED IN THE SHED) and start walking, keeping your pace count and red in the shed, until you reach your objective. Dead reckoning is usually not as accurate as terrain association and you must constantly update your location on your map, while keeping separate track of distance and azimuth changes, if any, about once every 30 minutes. You might also have to cross terrain that you would avoid during a daytime movement. The longer the movement the larger error involved so, if possible, break the overall movement into several short legs with multiple en route check or way points. During night navigation, you must illuminate your compass dial without ruining your night vision and/or compromising yourself in the process. Hold your compass and flashlight under your poncho or shirt for a minute or so. During a night movement, your rate of travel will be much slower than during a day movement, and your stride will be shorter, affecting your pace count.
Keeping your pace count is important when using dead reckoning. One device used to record your pace are Ranger Beads. Here is a link to a photo and explanation of how to make your own. You can also find them, ready-made, online. http://lifehacker.com/5850246/make-and-use-ranger-beads-to-measure-your-walking-distance . I keep a set in my map case and use them when navigating using dead reckoning. They’re basically beads, strung on a piece of gutted 550 cord, nine beads below a knot, four above it. Each bead on the bottom represents 100 meters. Each bead at the top represents 1,000 meters or 1 kilometer (1 click). For every 100 meters you count using your pace count, pull a 100 meter bead up, after you have traveled 1 click, pull the nine beads back down to reset and pull one 1 kilometer bead up. After 5 clicks, start them over. Not rocket science but they work.
When planning a movement using this method, it’s best to plan for several check points along the way. Good check points include linear man-made and natural terrain features that you will intersect on your azimuth such as, roads or trail crossings, streams, and ridgelines or valleys that you would not miss in the dark. They can also be used as a backstop to warn you have passed your objective. When planning your route using your map, measure off the distance to each en route checkpoint, note them and check each off as you reach them, noting them on your map as your current location.
Map features pitfalls. You can usually rely on natural terrain features being exactly where they are shown on the map. I say usually, with the exception of Ft. Drum, NY. When stationed there as a new infantry private, land nav. could be pretty frustrating. More often than not, when conducting a movement, we would walk directly into a new beaver pond or marsh that, of course, was not on the map. They seemed to number in the hundreds and they constantly popped up in new locations. It could be frustrating but we got pretty good at navigating around them while not getting off azimuth and losing our pace counts. Man made features, however, can get you in a boat-load of trouble. Structures are torn down and new ones are built. New roads are paved, and anybody with a four-wheel drive truck can rough-in a new dirt road. Old logging or forest service roads are neglected and can grow over. Depending on the age of the map, areas that are shown as forested have been logged and areas that are shown as a clearing are overgrown. My best advice is to look for man-made features such as paved roads, dirt roads and clearings on your map anyway, measure the distance to them and, as you get closer to the checkpoint, slow down and start looking closely for that road bed or newly planted area. If you find it great, note it on your map. If you don’t find it, go on to the next checkpoint. If you happen upon a dirt road or other feature that’s not on the map, you can make a notation for future use. Our maps, of the AO we operate in, have been updated in this manner. Again, always keep track of your current location as you move. If you find you are lost, dial a 180 degree reversal into your compass, and return on the back azimuth, using your current pace count, back to your previously known checkpoint.
Offsets: When dead reckoning to your objective, try to intentionally offset to one side or the other of the objective along a linear feature, such as a stream or road, so that you will know to move left or right to the final objective, or checkpoint, once you reach the feature.
Attack points: Use easy to find terrain features, that are in close proximity of your final objective, to get you close to your objective. Examples include road/stream intersections.
Handrails: Rather than walking on roads, ridgelines, next to streams, in valleys or any other linear feature, move parallel to it, just within eyesight, dependant on cover and concealment. This technique is not only tactically significant to a small unit, but sometimes movement is easier, faster, and quieter while hand railing along a stream rather than through thick vegetation, loose slippery rocks and water in the stream bed not to mention the risk of skylighting when walking a ridgeline, or compromise if walking a road, which is a linear danger area and high-speed avenue-of-approach combined.
Terrain association is the always the preferred method of movement, when environmental conditions permit. Again, determine your present location on your map by triangulation, orient the map to the terrain around you, then determine an azimuth to your objective. Using terrain analysis with your map, you might determine that a direct azimuth route-of-march is not the best course while taking advantage of the terrain to make your movement easier or to mask your movement. You may plan a circuitous route, using several different terrain features along the way to guide you and to use as en route checkpoints/waypoints. I would recommend that you determine a general azimuth for each leg but it’s not necessary, since you can always triangulate to visible terrain features along the way. Again, keep your map location updated as you move. Once you are close to your objective, you can switch to dead reckoning from a nearby attack point to guide you precisely to the target.
Rounding it out with some thoughts from DTG
Essential Skills: Impact of Magnetic Declination on Accuracy
Comments on the last post on Magnetic Declination disagree with, or at least minimized the importance of magnetic declination with the general feeling that, ” …’15 degrees’ isn’t that much of an error” or, “15 degrees will only result in a little bit of extra walking..,” or “I can get where I’m going…”
Now, I’m sure that guys and gals out there who’ve been hunting in one area or another (no matter how large) all their lives and have well used topographical 7.5 minute maps can get from point A to point B and so on with a cursory look at their map and shooting a general bearing with their compass. The primary tool they use is familiarity with the AO (a good thing) and terrain association with the compass used as a back up. Ergo, they may not think they need to worry about declination. And, in that particular scenario, those making claims like that are most likely 100% correct.
For discussion’s sake, let’s get into a SHTF scenario or some other situation where the person is using a new map and is unfamiliar with the territory. Say running a security patrol with your NPT with the task of linking up with a neighboring NPT at a particular location at a particular time. If the NPT’s in the scenario don’t concern themselves with accurate grid azimuth conversion to magnetic conversion, lives could be at stake, and the link up will most likely not occur.
Experienced navigators backed up by the facts regarding magnetic compasses and the magnetic ‘North Pole’ will quickly tell you that if you don’t account for the local declination, you stand a great chance of not reaching your objective (which may be getting back to your truck or home or reaching and injured person or whatever you can think of) or becoming lost yourself.
If you’re looking on your map and figure you need to take a 78 degree azimuth, and set your compass accordingly, and you haven’t either adjusted the compass for the local declination (difference between Magnetic North and True North, either East or West), you have a proportionate error when you shoot your azimuth (bearing) to start your walk. Here’s the error factor of being off by various degrees computed to distance from the target:
1 degree of error at 1,000 meters = 17.5 meters off target (or 19 yards)
5 degrees of error at 1,000 meters = 87.5 meters off target (95 yards)
8 degrees of error at 1,000 meters (my AO) = 140 meters off target (153 yards)
10 degrees of error at 1,000 meters = 175 meters off target (191 yards)
16 degrees of error at 1,000 meters = 280 meters off target (306 yards)
21 degrees of error at 1,000 meters = 367.5 meters off target (401 yards)
That’s for a 1 click leg (1,093 yards). Now, let’s multiply that to, say, a 7 click straight line walk. Drum roll: 2,572.5 meters off target at the end of that little 7 click jaunt.
Now, for discussion’s sake, let’s make our walk shorter. We’ll use the maximum variation in the US – 21 degrees East (Washington State) for a short, 3 click walk. Drum roll: 1,102.5 meters/1,205 yards (even backing it down to the declination in my AO, 8 degrees, it comes out to 420 meters/459 yards – almost half a click – which is a LOT in a rural/wilderness environment). Over a click off your target from the get go; drift, deviation, and pace count error haven’t been factored in yet.
That’s where you are; imagine where you will be when you think you’re at the end of your first leg. The mind boggles. For fun in this mental exercise, add a little thing called, “night” to the equation. Now, for added flavor, consider when the map isn’t matching up to the terrain and you’re positive that your on the right azimuth, the disorientation (something that occurs with little notice) that can add to all the things you’re dealing with, and oh yes, human error in our calculations.
So, if you’re serious about learning or improving your land navigation skills, find a good course and go to it. Or join a local orienteering club. If you want to attend ours, here’s the link. It’s going to be in April 2015. One day will be spent on the academics; one day will be spent in the field getting some, “dirt time,” rain or shine.