Archive for the ‘Land Navigation’ Category
Directional Aids!
Identify & Movement to Landmark!
When navigating with a compass on a specific azimuth/direction, never walk with the compass in the open position. It’s not only hard on the compass, it further subjects it to possible damage ; plus, it’s not accurate when used this way.
It is better to identify an easily recognizable landmark on the azimuth/direction line of movement. These landmarks or steering marks can not be based on map study but rather what you see on the ground. They are singularly selected and progressively replaced as the march continues. They’re normally on or near the highest point along the azimuth/direction line, and you would navigate from one steering mark to the next. Considerations for a good steering mark would be:
- Easy to recognize as you progress forward based on color, size, and/or shape;
- The highest and furthest steering mark is normally the best. It should be continuously visible as you move forward.
- Steering marks at night should be based on unique shape not color (at night red appears black).
- During hours of limited visibility or when natural steering marks are not available, use situational imagination and expedience. Example: Send out a human (far as you can see): 1. direct them to azimuth line; 2. move to them; 3. repeat the process. It’s slow but workable.
There are binoculars and/or night vision devices that would simplify movement during the hours of limited visibility.
Navigate by Dead Reckoning!
No Room for Error!
Movement by Dead Reckoning consists of two basic, fundamental Map Reading/Land Navigation steps:
- The use of a protractor and graphic scales to determine the direction/azimuth and distance from one point to another on a map.
- Use of a compass and some means of measuring distance to apply this information on the ground.
Essentially, Dead Reckoning normally begins with the determination of a polar coordinate on the map and ends with the process of finding it on the ground. This process will require the knowledge and ability to apply advanced Map Reading/Land Navigation and Compass principles, techniques, and skills.
Map/Ground Comparison!
Movement by Map/Ground Comparison!
Movement by Terrain Association is quicker, less tedious, more forgiving and fun than is Dead Reckoning (dependent on previous location/computations). However, there will be times during movement by Terrain Association when you will need to stop and confirm your position through either plotted or estimated resection.
Errors made using Terrain Association can be corrected fairly easily because you are comparing what you see on the map with what you find on the ground. But, you must be ever mindful that a map is only a previous picture of the earth’s surface drawn to scale. It may or may not be totally representive of what you’ll find on the ground. Some features, especially man-made/influenced, will change with time.
- Matching the Terrain to the Map using Terrain Features: By observing the map’s contour lines, determine Major Terrain Features (hilltop, valley, ridge, depression, and saddle). From a vantage point, compare what you see on the map with what you should see on the ground.
- Compare Vegetation Depicted on the Map: But, be conscious/mindful that it can change overnight from natural accidents or man-made influences.
- Using the Hydrography: Use in-land bodies of water; their shapes, sizes, and direction of water flow.
- Man Made Features: This is an important part of Terrain Association. You should be familiar with the symbols used; consider the map’s age; but, most important, nothing is permanent – if it can be built, it can be torn down!
This method of ground movement will require not only knowledge but a competency in Map Reading, Compass, and Navigational Skills.
Map Orientation!
Map/Compass/Ground Orientation!
A needed preliminary step to map/ground association is to orient the map with the lay of the land. After orientation, if you plot your location on the map, and while doing it see a hill top 2000 yards to the northwest, you should be able to look up and see that same hill top to your right-front at 2000 yards.
The method used to orient the map with the ground depends on what you’re doing. If all you want is a quick analysis, determine north (compass) and point the top of your map in that direction, and map is generally oriented. But, if you’re intention is to determine/plot directions or azimuths on the map and accuracy is critical, the method used should be exact, deliberate and allow no errors:
- Place the map on a flat surface;
- Open compass and place it (straightedge) parallel with a North/South grid-line.
- Keeping the compass aligned, as directed above, carefully rotate the map/compass (together) until the magnetic arrow is below the fixed black index line of the compass (almost oriented);
- To further compensate for the small Grid/Magnetic (GM) angle change, rotate map and compass in the direction of the magnetic arrow in the declination diagram. Whether movement is right or left, rotate the map/compass that small amount (degree/mils) indicated by the G/M angle. The number of degrees/mils of rotation will be reflected under the fixed index line of the compass.
The map and compass are now oriented in accordance with map’s Declination Diagram.
Does it look that way on the map?
Map/Ground Comparison!
We have already established that the top of the map always reflects North, map’s right: East, bottom: South, and the left (as you look at it) would be West.
Based on the vast information contained in the map, including the many different types of terrain and other features; coupled with your Map Reading/ Land Navigation knowledge and skills, it is fairly simple to start visualizing how the land/terrain must appear in relation to your position on the map.
This, couple with your knowledge of the compass and various land navigational techniques, will assist in your map study and terrain/map association. It should culminate with committed movement on the ground. The key to its success is in preparation; it must be as-slow-as necessary, methodical, and very deliberate.
Pace Count!
You do the pace-count; I'll keep us on course!
Determining distance is extremely difficult and the most common source for error in cross-country land navigation.Establishing an accurate pace-count is very important. A pace is equal to one normal step. You must determine how many paces it takes you to walk 100 meters/yards. The average pace for an adult male is 30 inches in length. However, the following, sustained conditions will affect that pace and must be considered/accounted for:
- Pace lengthens on a down-slope and shortens on an up-grade;
- Head-winds shorten the pace – tail-wind will increase the pace;
- Sand, gravel, mud, snow, and similar conditions tend to shorten the pace;
- Falling snow, rain, or ice cause the pace to be reduced;
- Excess clothing and boots with poor traction will affect the pace length;
- Poor visibility such as fog, rain, or darkness will shorten your pace.
In the absence of electronic devices, establish the minimum of a 100 meter confirmation course and validate your pace-count. Terrain and environmental conditions should be duplicated as-much-as possible.
Extension for the Memory!
Keep It Simple!
If your game is serious land navigation, there will be times when all you have that is useful to navigate with is an azimuth, your compass, the straight-line distance in yards/meters to where you‘re going, and your two feet to get you there.
For me, the difficulty is not following the compass reading but rather keeping track of the distance traveled. When you get 10,000 meters into a 20,000 meter leg, things have a tendency to start running together – was that 9,500 or 9,600 meters. Your memory will play tricks on you if you don’t have a device, system, or way of keeping track of what you’ve done.
Ideally, you’ll have a trekking buddy that will do that for you, and all you’ll have to do is stay on course. A simple thing I’ve done, to keep track of the distance traveled, was to use a couple foot-long, 1/4 inch ropes/cords. Each time I walked 100 meters, I would tie a knot in one of the ropes. When I had ten knots in the rope, I would tie one knot in the other rope. You would continue this process until the desired distance has been traveled. What is critical about this is that you must know how many steps it takes for you to walk 100 meters.
Compass to Cheek Method!
Sighting the Compass!
The Compass to Cheek method of holding a Lensatic Compass is used almost exclusively for sighting. Obviously, if using, there must be enough light to see the far distant aiming point/object. The following sequential steps can be used to place the compass into operation:
- Open the Lensatic Compass cover (w/sighting wire) to a vertical position.
- Pull up the sighting lens slightly, place thumb through the thumb loop and provide a steady base by forming a fist around the thumb with four remaining fingers.
- Take second hand and grasp supporting hand and depict in diagram above.
- Lift compass to cheek and look through the rear-sight slot and align the front-sight hairline with the far distant aiming point/object.
- Glance down at the dial through the eye lens and read the direction/azimuth in either degrees or mils.
Remember, the direction/azimuth obtained with a Lensatic Compass is a magnetic reading and must be converted to a grid direction/azimuth before plotting on a map.
Using a Lensatic Compass!
Centerhold Position!
There are several Lensatic Compass holding techniques; however, in the interest of expedience, this posting will cover the most common and generally preferred method. The Centerhold Technique is assumed by:
- Open the compass (fullest extent).
- Move rear sight to the upright position (unlocks floating dial).
- Place thumb through the thumb loop; form a steady base with third and fourth fingers; extend index finger along side the compass; place other thumb between the rear sight and the compass dial; extend the index finger along the other side of the compass and remaining fingers around the other hand; pull your elbows into your side and turn your body in the direction of the target/object for azimuth reading/determination.
To determine the azimuth, once the compass is pointing at the target, look down and read the azimuth from beneath the fixed black index line. Remember, this is a magnetic reading and must be converted to Grid before plotting on a map.
Compass Handling!
Magnetic, Lensatic Compass!
A Lensatic Compass does not require a large amount of maintenance. However, prior to use, it should be inspected for operability, insuring: 1. The sight wire is serviceable and in place; 2. Neither the sight glass or crystal face is broken; 3. The floating dial is not stuck and functions freely/properly.
The compass should be checked periodically to insure it delivers a correct reading. This is done by comparing the applicable compass direction/azimuth reading with the known surveyed data (direction/azimuth) to the same aiming point. If the compass is off more than 3 degrees, it shouldn’t be used. When not in use, the eye lens of the Lensatic Compass should be in the down position, locking/securing the floating dial and also providing protection to the crystal face/rear sight.
Metal objects and electrical sources will adversely affect a magnetic compass reading. Therefore, to preclude this from happening, the following minimum separation distances must be followed:
- Power Lines – 55 meters;
- Vehicles – 18 meters;
- Telephone or Barbed Wire – 10 meters;
- Small Metal Objects (rifle/pistol) – ½ meter.