FM 17-98 Chapter 9 Miscellaneous Field Data

CHAPTER 9

Miscellaneous Field Data

This chapter includes information that may prove useful to the scout platoon's leaders and crewmen during the execution of platoon missions. This material is not covered elsewhere in this manual; some portions were taken from previously published sources, including FM 17-98-1, now rescinded.

CONTENTS
Section 1	Reconnaissance Overlay Symbols
Section 2	Field Expedient Formulas
Section 3	Measurement Conversions
Section 4	Field Expedient Antennas
Section 5	Survival
Section 6	Enemy Weapons, Vehicles, and Aircraft

SECTION 1 — RECONNAISSANCE OVERLAY SYMBOLS

Figure 9-1 outlines a variety of symbols that scouts can use to illustrate reconnaissance data on their overlays. An example of how these graphics are used in the overlay is illustrated in Figure 9-2. Figure 9-3 shows symbols for various materials, facilities, equipment, and services. The graphics in this section are adapted from information provided in FM 5-170.

Figure 9-1. Reconnaissance overlay symbols.

Figure 9-1. Reconnaissance overlay symbols (continued).

Figure 9-2. Example of overlay graphics.

Figure 9-3. Material, facility, equipment, and service symbols.

SECTION 2 — FIELD EXPEDIENT FORMULAS

This section covers formulas that scouts will find useful in water crossing operations and in determining the slope of a road or other piece of terrain. The information is adapted from FM 5-34.

FORMULAS FOR WATER OBSTACLES

Width

Scouts can measure the width of a river or stream using one of several available methods:

Stretching a string or measuring tape across the river or stream.
Using a map scale.
Using a compass and the basic mathematical computation illustrated in Figure 9-4.

Figure 9-4. Measuring stream width with a compass.

Velocity

Scouts can measure the velocity of the current of a river or stream using the procedures shown in Figure 9-5.

Figure 9-5. Measuring stream velocity.

SLOPE COMPUTATION

Figure 9-6 illustrates several methods that scouts can use to determine the slope of a piece of ground, whether it is an established roadway or a cross-country route. These procedures are included:

Using a clinometer.
Using a slope computation formula in which horizontal and vertical distances are computed based on the map scale and contour differences for the road or terrain.
Using a hasty method in which pacing and eyesight are used to determine horizontal and vertical distances for the slope computation formula.

Figure 9-6. Slope computation (road gradient).

SECTION 3 — MEASUREMENT CONVERSIONS

This section includes tables covering the basic computations for converting English measurements to their metric equivalents. The following conversions are included:

Table 9-1 lists conversions for common distance measurements (inches to centimeters; feet to meters; yards to meters; miles to kilometers).
Table 9-2 shows conversions of miles per hour to kilometers per hour.

Table 9-1. English to metric distance measurement conversions.

INCHES to CENTIMETERS
1 inch = 2.54 centimeters
2 inches = 5.08 centimeters
3 inches = 7.62 centimeters
4 inches = 10.16 centimeters
5 inches = 12.70 centimeters
6 inches = 15.24 centimeters
7 inches = 17.78 centimeters
8 inches = 20.32 centimeters
9 inches = 22.86 centimeters
10 inches = 25.40 centimeter
20 inches = 50.80 centimeters
30 inches = 76.20 centimeters
40 inches = 101.60 centimeters
50 inches = 127.00 centimeters
60 inches = 152.40 centimeters
70 inches = 177.80 centimeters
80 inches = 203.20 centimeters
90 inches = 228.60 centimeters
100 inches = 254.00 centimeters

FEET to METERS
1 foot = 0.30 meters
2 feet = 0.61 meters
3 feet = 0.91 meters
4 feet = 1.22 meters
5 feet = 1.52 meters
6 feet = 1.83 meters
7 feet = 2.13 meters
8 feet = 2.44 meters
9 feet = 2.74 meters
10 feet = 3.05 meters
20 feet = 6.10 meters
30 feet = 9.14 meters
40 feet = 12.19 meters
50 feet = 15.24 meters
60 feet = 18.29 meters
70 feet = 21.34 meters
80 feet = 24.38 meters
90 feet = 27.43 meters
100 feet = 30.48 meters

YARDS to METERS
1 yard = 0.91 meters
2 yards = 1.83 meters
3 yards = 2.74 meters
4 yards = 3.66 meters
5 yards = 4.57 meters
6 yards = 5.49 meters
7 yards = 6.40 meters
8 yards = 7.32 meters
9 yards = 8.23 meters
10 yards = 9.14 meters
20 yards = 18.29 meters
30 yards = 27.43 meters
40 yards = 36.58 meters
50 yards = 45.72 meters
60 yards = 54.86 meters
70 yards = 64.00 meters
80 yards = 73.15 meters
90 yards = 82.30 meters
100 yards = 91.44 meters

MILES to KILOMETERS
1 mile = 1.61 km
2 miles = 3.22 km
3 miles = 4.83 km
4 miles = 6.44 km
5 miles = 8.05 km
6 miles = 9.66 km
7 miles = 11.27 km
8 miles = 12.87 km
9 miles = 14.48 km
10 miles = 16.09 km
20 miles = 32.19 km
30 miles = 48.28 km
40 miles = 64.37 km
50 miles = 80.47 km
60 miles = 96.56 km
70 miles = 112.65 km
80 miles = 128.75 km
90 miles = 144.84 km
100 miles = 62.14 km

Table 9-2. Miles per hour to kilometers per hour conversions.

IMILES PER HOUR
1 mph
2 mph
3 mph
4 mph
5 mph
6 mph
7 mph
8 mph
9 mph
10 mph
15 mph
20 mph
25 mph
30 mph
35 mph
40 mph
45 mph
50 mph
55 mph
60 mph
65 mph
70 mph
75 mph
100 mph

KILOMETERS PER HOUR
1.609 kmph
3.22 kmph
4.83 kmph
6.44 kmph
8.05 kmph
9.66 kmph
11.27 kmph
12.87 kmph
14.48 kmph
16.09 kmph
24.14 kmph
32.19 kmph
40.23 kmph
48.28 kmph
56.33 kmph
64.37 kmph
72.42 kmph
80.47 kmph
88.51 kmph
96.56 kmph
104.61 kmph
112.65 kmph
120.70 kmph
160.94 kmph

SECTION 4 — FIELD EXPEDIENT ANTENNAS

During the execution of the scout platoon's missions, it is very likely that an antenna will be broken or damaged, resulting in a reduction or total loss of communications ability. This section covers how to repair broken or damaged antennas; it also provides instructions on how to construct replacement antennas that will allow the platoon to restore internal communications and to regain communications with the battalion task force or cavalry troop.

ANTENNA TYPES

Direction and distance are critical factors in determining what type of antenna to use based on the platoon's communications requirements. Antennas are categorized in three basic types. This discussion explains how to construct each of these antennas, which have the following capabilities and limitations:

An omnidirectional antenna allows the operator to communicate in all directions.
A bidirectional antenna allows the operator to communicate in either of two directions.
A unidirectional antenna allows the operator to communicate in one direction.

Omnidirectional antennas

Vertical antennas are omnidirectional. A vertical antenna can be improvised by using a metal pipe or rod of the right length held erect by guide wires. The lower end of the antenna should be insulated from the ground by placing it on a large block of wood or other insulating material. A vertical antenna can also be a wire supported by a tree or wooden pole.

To construct an omnidirectional antenna, use the quick reference chart in Table 9-3 to first determine the length of WD-1 wire needed. Attach an insulator to one end of the wire and insert the other end, once it has been stripped of all insulation, into the antenna connector on the radio. Secure the wire to the improvised mast and erect the mast. The radio can now transmit and receive. If a tree is used as the mast, tie a rope to the insulator end of the wire, throw the rope over a limb, and pull the insulator up until the wire is vertical.

Table 9-3. Quick reference chart for omnidirectional antennas.

Operating frequency (MHz)
30
32
34
36
38
40
43
46
49
52
55
58
61
64
68
72
76

Wire/element length
2.38 meters (7 feet 10 inches)
2.23 meters (7 feet 4 inches)
2.10 meters (6 feet 11 inches)
1.98 meters (6 feet 6 inches)
1.87 meters (6 feet 2 inches)
1.78 meters (5 feet 10 inches)
1.66 meters (5 feet 5 inches)
1.55 meters (5 feet 1 inch)
1.46 meters (4 feet 9 inches)
1.37 meters (4 feet 6 inches)
1.30 meters (4 feet 3 inches)
1.23 meters (4 feet 0 inches)
.17 meters (3 feet 10 inches)
1.12 meters (3 feet 8 inches)
1.05 meters (3 feet 5 inches)
.99 meters (3 feet 3 inches)
.94 meters (3 feet 1 inch)

If insulated wire is used, be sure to loop the wire around the handle of the radio before attaching it to the antenna connector. If the antenna is made of bare wire, use a stake and insulator to keep the antenna wire from pulling out of the antenna connector on the radio.

Bidirectional antennas

Bidirectional antennas will normally be used as field expedient retransmission stations. The electrical length of the antenna is measured from the antenna terminal on the radio set to the far end of the antenna. The best performance can be obtained by making the antenna longer than necessary and then shortening it, as required, until the best results are obtained.

For this antenna to function efficiently, the ground terminal of the radio set should be connected to a good earth ground. A 100-foot-long wire antenna will work when the radio is operating in the 30 to 80 MHz frequency range. For high-frequency operation, the antenna wire must be longer. This antenna will improve the range of the radio in the direction the wire is stretched.

To construct a bidirectional antenna, first erect a pole or select a tree in line with the desired direction of communications. The antenna should be at least 20 feet high. If a tree is used, ensure that the wire does not come in contact with any of the branches. Tie a rope to the pole or tree. While holding the other end of the antenna wire, pace off 100 feet in the direction in which you want to communicate. Tie an insulator to the end of the wire. Now prepare a mast or pole for the second support.

To make a pulley, tie a length of WD-1 wire or nylon rope to the top of the mast. Put a rope or wire halyard through the loop and attach it to the other side of the insulator. Leave enough rope to pull the antenna up once the mast is erected. Attach 25 feet of WD-1 wire to the antenna side of the insulator. Make a good electrical connection because this is the antenna lead-in.

Put up the second support about 6 feet beyond the end of the 100-foot antenna. This will allow for insulators at each end. Pull up the halyard until the antenna is level and tie the end to the supporting pole. Connect the WD-1 wire lead-ins to the radio, which is now ready for operation.

Unidirectional antennas

Dismounted patrols and units of company size and below can greatly improve communications by using field-expedient unidirectional antennas. Such antennas allow them to broadcast farther and receive more clearly. The V-antenna is the easiest antenna of this type to construct. It consists of two wires that form a V, with the open end pointing to the desired direction of transmission/reception.

To construct a V-antenna, first select a mast that is about 10 feet in length. Cut a section of WD-1 wire that is the correct length for the selected operating frequency; secure one end to the connecting plug on the radio. Holding the center of the wire, secure it to the main mast, wrapping it around the top of the mast several times. Take the two ends and secure them to two separate masts, forming a V shape, or secure them to the ground diagonally to form the V.

Attach an insulator to both ends of the wire, about 2 feet from the end of each. Ground the radio by wrapping a length of WD-1 wire around the radio handle and grounding it to a stake in the ground.

REPAIR TECHNIQUES

Whip antennas

The following paragraphs cover procedures for repairing two types of whip antennas. These procedures will allow the vehicle crew to regain communications until a replacement antenna can be obtained.

Metallic antennas. To repair a broken metallic antenna, first scrape the paint three to six inches off the ends of the broken sections; this can be accomplished using sand, rocks, metal, or a knife. Be sure to remove as much paint as possible. Once the paint has been removed, overlay the cleaned ends of the antenna and wrap them tightly together using 12 to 15 inches of copper wire or stripped WD-1 wire. Place a dry stick, MRE spoon, or some other stiff support on each side of the splice and secure this with tape, WD-1 wire, or whatever is available.

Fiberglass antennas. To repair a fiberglass whip antenna, measure a 5-foot length of coaxial cable. Strip the rubber sleeve from the cable, and separate the braided shield from the center conductor. Lash a dry, 10-foot pole to the antenna base. Tape the center conductor to the top of the pole and the braided shield to the bottom. Tape the stripped cable in several more places along the pole so it will stay in place. If there is a twist-lock connector on the cable, connect it to the radio; if not, wedge the center conductor firmly into the antenna connector and attach the braided shield to a screw head on the radio case.

Wire antennas

Emergency repair of a wire antenna may involve the repair or replacement of the wire used as the antenna or transmission line or the repair or replacement of the assembly used to support the antenna. Ensure that the replacement wires are as close as possible to the original wire length and the connections are soldered when possible. Use electrical tape, if available, for added support. Antenna supports can be replaced using trees, tent poles, or telephone poles. To replace guide ropes, use tent ropes, ropes from tarps, or webbed belts.

Field-expedient repair items

Table 9-4 lists items that can be helpful in making field expedient repairs to various pieces of equipment.

Table 9-4. Useful materials in field expedient repairs.

ORIGINAL ITEM	FIELD EXPEDIENT REPAIR ITEM
Antenna wire	WD-1, barbed wire, electrical wire, coaxial cable
Antenna mast	Trees, strikes, lance pole, telephone pole
Coaxial cable	WD-1, electrical wire
Antenna guide wire	Wire, cloth belts
Whip antenna	Wire, WD-1, coaxial cable
Insulators	Plastic rings, MRE spoons, plastic bags wood, rope, bottles

SECTION 5 — SURVIVAL

Survival is largely a matter of mental outlook. The will to survive is the most important factor. In a group or alone, people faced with survival in the wild will experience emotional problems resulting from shock, fear, despair, loneliness, and boredom. In addition to these mental hazards, injury, pain, fatigue, hunger, or thirst will tax the will to live.

Soldiers who are not mentally prepared to overcome all obstacles and to expect the worst will find their chances of survival greatly reduced. They can alleviate the shock of being isolated behind enemy lines, in a desolate area, or in enemy hands by remembering the following survival tips, keyed to individual letters of the word "survival":

S - Size up the situation by considering the individual, the country, and the enemy.
U - Undue haste makes waste. Do not be too eager to move. Do not lose your temper.
R - Remember where you are.
V - Vanquish fear and panic. Remember that fear is normal. Controlling fear when injured is especially difficult, and loneliness can cause panic. Planning an escape can keep your mind occupied.
I - Improve the situation. Learn to put up with new and unpleasant conditions.
V - Value living. Hope and a real plan for escape reduce fear and improve the chance of survival. Health and strength must be conserved. Hunger, cold, and fatigue lower efficiency and stamina. Remember that your goal is to get out alive.
A - Act like the natives.
L - Learn basic skills.

FOOD AND WATER

Water collection

Without water, the chances of survival are nil and all the food in the area means nothing. When there is no surface water, it will be absolutely necessary to tap into the earth's water table for ground water. In rocky soil, look for springs and seepage; in loose soil, look for ground water along valley floors or on the slopes bordering the valley. Springs and seepage can also be found above the high water mark of rivers and streams. In desert or arid lands, natives often know where lingering surface pools are located in low places and will cover these with brush heaps.

Places that are visibly damp, where animals have scratched, or where flies hover indicate recent surface water. Collect dew on clear nights by sponging it up with a handkerchief; in heavy dew, it should be possible to collect about a pint an hour. On mountains, dig in dry stream beds, where water can often be found under the gravel. In snowfields, put snow in a container and place it in the sun, out of the wind.

A water still can be built using a 6-foot-square piece of clean plastic, a 2-to-4-quart container, and a 5-foot piece of flexible tubing. First pick an unshaded spot for the still, and dig a hole about 3 feet across and about 18 inches deep. Place the container in the bottom of the hole and tape one end of the flexible tube inside. Lay the plastic sheet over the hole and pile enough dirt or rocks around the edge to hold it firmly in place. Place a fist-size rock in the center of the plastic sheet and adjust the sheet as necessary to bring it to within a couple of inches of the container. Heat from the sun will evaporate the ground water, which then condenses under the plastic. The water trickles down and drops into the container; it can be drunk using the tubing.

Food sources

There are at least 300,000 different kinds of wild plants in the world. A large number of them are edible, although some are tastier than others. Never eat a large quantity of a strange food without first testing it. Prepare a cooked sample, then take a mouthful, chew it, and hold it in your mouth for five minutes. If it tastes good, it is generally safe to eat. If the taste is bitter or you develop a burning or nauseating feeling, do not eat the rest. In general, if you observe an animal eating the plant, it will be safe for you to eat. Avoid eating plants that have milky juices; they are not fit for consumption.

Animal food contains the most nutrient value per pound. Anything that creeps, crawls, swims, or flies is a possible source of food. Small game animals, such as rabbits and mice, travel on paths through vegetation. Set traps or snares on or over these trails. Fishhooks can be made from items with points or pins, such as nail files or collar insignia, or from bird bones, fish spines, and pieces of wood.

Hot meals are beneficial to morale, and proper heating kills many germs. Boiling is the best way to cook food in the wild; it preserves the food's natural juices and does not require a large fire.

SHELTERS

Construct a shelter based on whether you need protection from rain, cold, heat, sunshine, or insects and on how long you will be camped. Pick the location for a camp carefully. Make sure it is in a concealed location away from trails or roads. Try to camp near food and water sources. Do not make camp at the base of a steep slope or in areas threatened by avalanches, floods, rockfalls, or battering winds. Ponchos, tarps, palm fronds, limbs, and branches can be used to build shelters. In snowfields, snowcaves or igloos can be constructed for shelter.

SECTION 6 — ENEMY WEAPONS, VEHICLES, AND AIRCRAFT

This section provides the scout platoon members with a guide to some of the common armored vehicles and attack helicopters with which the platoon may come in contact on the battlefield. For the scout platoon to complete its mission, it must stay alive. It is therefore very important that the scouts know in detail what enemy weapon systems are on the battlefield as well as their ranges, capabilities, and the manner in which they will be employed. Figure 9-7 lists specifications for various potential enemy systems.