a. One of the key requirements for the delivery of accurate predicted fire on a target is accurate target location. To successfully perform his duties, the observer must be able to determine an accurate position of a target on the ground. The keys to accurate target location are as follows:
- Self-locating to within 100 meters each time he moves.
- Using prominent terrain features to relate potential
target areas to grid locations on the map.
- Making a thorough study of terrain by drawing a
terrain sketch (in a static environment).
- Associating the direction in which he is looking with a
direction line on the map.
- Ensuring that a planned target is always a recognizable point on the ground (except for "cannot observe" missions).
b. Terrain-map association may not be possible when maps are unavailable or the terrain has no features. Using large-scale maps (1:250,000 or larger) may also make terrain-map association difficult. In these situations, the use of position-locating systems or other navigational aids is essential for observer self-location and the accurate location of targets.
Once a thorough terrain-map study has been conducted, the observer will be well prepared to locate targets. Accurate location of targets is critical to achieving first-round effects on targets. Often, errors in target location can be corrected only by adjusting fires onto a target, thereby losing the surprise and effects of a fire-for-effect mission. The use of position-locating systems or laser devices that are operating from known locations can greatly enhance target location. The three methods of target location available to the observer are as follows:
- Polar plot-the observer describes the target location in relation to himself.
- Grid coordinates-the observer locates the target by giving the actual grid location.
- Shift from a known point-the observer describes the target location in relation to a point of known location (planned target or known point).
a. Polar Plot. In this method, the observer's location must be known to the FDC. The observer does not need a map. This method is easy and quick; however, the observer must transmit his location by secure means to avoid revealing his location to the enemy. Also, in a mobile situation it is more difficult for the observer to determine his location and send it to the FDC. The steps used in the polar plot method are discussed below (also see Figure 3-1).
Figure 3-1. POLAR PLOT
(1) Determine the observer-target (OT) direction by
one of the methods discussed in paragraph 3-3.
(3) Determine a vertical shift, if significant. Determine an up or down shift if the difference between the observer altitude and the target altitude is significant (greater than 35 meters). See paragraph c(5) below for a further discussion of vertical shift.
|NOTE: Target location methods using lasers provide for greater accuracy and are discussed in Appendix A. The laser range finder AN/GVS-5 and the G/VLLD AN/TVQ-2 are examples of equipment available.|
b. Grid Coordinates. Target location by grid coordinates is a natural extension of the polar plot method. The observer's location need not be known to the FDC. The observer normally locates targets to an accuracy of 100 meters (six-place grid). He does this by polar-plotting on the appropriate map and then reading the grid. When additional accuracy is required (for example, for registration points and known points), the observer should locate targets to the nearest 10 meters (eight-place grid). Although there is no requirement to send target altitude, transmitting it to the FDC increases the accuracy of the initial fires.
c. Shift From a Known Point. The observer may have one or more known points in his area of responsibility. These are readily identifiable points whose locations are known to both the observer and the FDC. The observer does not need a map to use this method; he needs only a known point. The steps in locating a target by shift from a known point are described below.
(1) Identify to the FDC the known point to be used;
for example SHIFT KNOWN POINT 1.
(2) Determine the OT direction. This direction can be a grid azimuth (the preferred method) or a cardinal direction. Examples are (grid azimuth) DIRECTION 4360 and (cardinal direction) DIRECTION, SOUTHWEST.
(3) Determine a lateral shift from a known point to the OT line. If the angular deviation from the observer-known point line to the OT line can be determined, a shift in meters can be computed by using the mil relation formula, W = R x m (Figure 3-2). This formula is based on the assumption that an angle of 1 mil will subtend an arc of 1 meter at a distance of 1,000 meters.
Figure 3-2. MIL RELATION FORMULA
The observer knows that the distance from his location
to the known point (CHURCH) is 2,500 meters. He also
knows the direction is 850 mils. With his binoculars, he
measures an angular deviation of 62 mile from the
church to the target. He calculates the lateral shift as
follows (Figure 3-3):|
2500 / 1000 = 2.5
(2500 is already expressed to the nearest (100.)
W = R x m
W = 2.5 x 62
W = 155 meters, approximately 160 meters (The lateral shift is
expressed to the nearest 10 meters.)
Figure 3-3. LATERAL SHIFT
|NOTE: When a shift of greater than 600 mils is required, the accuracy of computing the lateral shift decreases. Another method of target location should be used.|
(4) Determine a range change along the OT line. The observer must determine whether the target is at a greater or lesser distance than the known point. The lateral shift gives the observer a point on the OT line ( T' ) assumed to be the same distance from him as the known point. If the target is farther away than the known point, the observer must add the estimated distance from T' to the target A (Figure 3-4) . If the target is closer, the observer must drop the estimated distance (Figure 3-4 B). The correction for a difference in distance between the known point and the target is expressed to the nearest 100 meters.
(5) Determine a vertical shift, if significant. If there is a significant difference (more than 35 meters) in altitude between the known point and the target, the observer must include it in his target location. If the target is at a higher altitude than the known point, the observer determines an up correction based on the difference in altitude (Figure 3-5). If the target is at a lower altitude, he must give a down correction based on the difference in altitude. Whether a vertical shift is sent or not depends on several factors. Normally, if the mission is an FFE mission, a vertical shift should be sent to improve accuracy. The observer should weigh the lime needed to determine and send a vertical shift against the time available. Experienced observers who can quickly determine differences in altitude should send a vertical shift when the difference in altitude is greater than 35 meters. When responsiveness is paramount, inexperienced observers should not try to send a vertical shift. The correction for a difference in altitude is expressed to the nearest 5 meters.
Figure 3-4. RANGE SHIFT
Figure 3-5. VERTICAL SHIFT
Determining direction is an essential skill for the observer. Direction is an integral part of terrain-map association, adjustment of fire, and target location. There are five methods by which to determine direction.
a. Estimating. With a thorough terrain-map analysis of his zone of operation, the observer can estimate direction on the ground. As a minimum, the observer should be able to visualize the eight cardinal directions (N, NE, E, SE, S, SW, W, and NW). Because of the inaccuracy of this method, it is the least preferred method of determining direction.
b. Scaling From a Map. Using a protractor, the observer can scale direction from a map to an accuracy of 10 mils.
c. Using a Compass. Using an M2 or a lensatic compass, the observer can measure direction to an accuracy of 10 mils. Care must be taken when a compass is used around radios or large concentrations of metal such as vehicles. Observers should move about 50 meters away from vehicles to avoid incorrect readings.
d. Measuring From a Reference Point. Using a reference point with known direction, the observer can measure horizontal angular deviations and apply them to the reference direction. Angular deviations may be measured with binoculars (Figure 3-6) or with the hand (paragraph 3-7). In measuring with binoculars, angular deviation is determined to the nearest 1 mil.
(1) The horizontal scale of the binocular reticle pattern
is divided into increments of 10 mils on both the M17
(Figure 3-6 A) and the M19 (Figure 3-6 B) binoculars.
(2) The vertical scale on the right of the M17 lens is not used by the FO in determining data for target location. The scale is used primarily by the infantry for sighting direct fire weapons (Figure 3-6 A).
(3) The vertical scales on the left and in the center of the M17 lens are divided into increments of 5 mils and are used in height-of-burst (HOB) adjustments (Figure 3-6 A).
|NOTE: Direction increases to the right and decreases to the left. To determine the direction to another point or target, apply the number of mils measured right or left of the reference point known direction by use of the RALS rule (right add; left, subtract). For example, the azimuth to the reference point is 2,100 mils. The target is 40 mils to the left of the reference point. The direction to the target is 2,060 mils (2,100 - 40).|
(4) The vertical scale in the center of the M19 lens is
divided into increments of 10 mils and is used in HOB
adjustment (Figure 3-6 B).
(5) The horizontal and vertical scales on the AN/GVS-5 laser range finder reticle are divided into increments of 10 mils. The centerlines are further divided with hash marks at 5-mil increments (Figure 3-6 C).
e. Using Other Measuring Devices. When properly oriented, the aiming circle or G/VLLD provides direction to the nearest mil. The heading indicator in an aircraft can be used by the aerial observer.
Figure 3-6. MEASURING ANGULAR DEVIATIONS WITH BINOCULARS AND AN/GVS-5
Once a direction to the target is determined, the observer must determine a distance to the target. There are several methods.
a. Laser. Lasers are the preferred means of determining the OT distance. When a laser is used, distance may be determined to the nearest 10 meters.
b. Flash-to-Bang. When it is necessary to verify OT distance, the flash-to-bang technique is helpful. Sound travels at a speed of approximately 350 meters per second. Use the following equation:
Elapsed time between impact and sound x 350 = Distance
Multiply the number of seconds between round impact (flash) and when the sound reaches the observer (bang) by 350 meters. The answer is the approximate number of meters between the observer and the round. (This procedure can also be used to determine the distance to enemy weapon muzzle flashes.)
The observer wants to determine the approximate distance from his position to a burst He begins counting when the burst appears and stops counting when he hears the sound. He counts 4 seconds. Therefore, the distance from the burst to his position is approximately 1,400 meters (350 x 4).
c. Estimation. In the absence of a more accurate method of determining distance to a target, the observer must estimate distance. The degree of accuracy in this method depends on several factors, such as terrain relief, time available, and the experience of the observer. Generally, the longer the observer remains stationary, the better he can use this technique. Some methods of estimating distance are discussed below.
(1) Mental estimation can by made by use of a known
unit of measure. Distance is estimated to the nearest 100
meters by determining the number of known units of
measure, such as a football field (100 yards), between the
observer's position and a target. For longer distances, the
observer may have to progressively estimate distance. To
do this, he determines the number of units of measure (for
example, 100 yards) to an intermediate point and doubles
(2) The observer should consider the following effects of estimating distances:
- Object appears nearer--
- When in bright light.
- When in clear air at higher altitude.
- When the observer is looking down from a height.
- When the observer is looking over a depression, most of which is hidden.
- When the observer is looking down a straight feature, such as a road.
- When the observer is looking over water, snow, or a uniform surface such as a cultivated field.
- When the background is in contrast with the color of the object.
- Object appears more distant--
- When it is in poor light or in fog.
- When only a small part of the object can be seen.
- When the observer is looking over a depression, most of which is visible.
- When the background is similar in color to that of the object.
- When observing from a kneeling or sitting position on hot days, especially when the ground is moist.
(3) When visibility is good, distances can be estimated by using the appearance of tree trunks, their branches, and foliage (using the naked eye) in comparison with map data (Table 3-1).
Table 3-1. ESTIMATION BY APPEARANCE OF TREES
(4) Distance can be estimated by using known
dimensions of vehicles and the mil relation formula (W =
R x m). By applying the width of a vehicle appearing
perpendicular to an observer as the lateral distance (W)
and measuring the width in mils (m), the distance can be
determined by solving the formula for range (R) in
thousands, or R = W / m. These data, when compared
with map data, will help an observer estimate distance. The
dimensions of selected equipment are shown in Table 3-2.
Table 3-2. EQUIPMENT DIMENSIONS
An observer sees an armored personnel carrier (BMP).
He measures its width (as seen from the side view) as 2
mils. Using the formula, he determines the distance as
R = W / m
m = 2 mils
W = 6.8 meters
R = 6.8 / 2 = 3.4, or 3,400 meters.
(5) The observer should always use map-terrain analysis
to help him estimate distance. A thorough study of the
terrain in comparison with features or objects identifiable on
the map can enhance the estimation of distance. The
observer should make a mental terrain walk to the target. He
compares the features or objects with those found on the
map along the same direction (OT line). The use of an
observed fire (OF) fan will help the observer in this.
Particular emphasis should be given to color contrasts along
the OT line. For example, the distance across successive
ridge lines or depressions in the distance may be identifiable
to the eye by only slight changes in color.
a. Another aid in target location in a static environment is the terrain sketch (Figure 3-7). This is a rough panoramic sketch of the terrain in the observer's area of responsibility prepared by the observer. Items that should be included in a terrain sketch are as follows:
- The skyline (horizon).
- Intermittent crests, hills, and ridges.
- Other natural terrain features (distinctive bodies of water and vegetation).
- Man-made features (buildings, roads, power lines, towers, antennas, and battlefield debris).
- Labels (reference points and targets).
b. Each labeled item should include as much information as possible to aid the observer. This information should be identified by using a T (see Figure 3-7). Reference point names, target numbers, or known point (kn pt) designations should be placed at the top of the T to identify the feature. Labels for direction (dir), distance (dis), altitude (alt), and grid should be placed on the left side of the T. The observer should fill in all available data for targets and known points. Reference points usually require only the direction to the reference point. The terrain sketch should also include the observer's name, date, and location. All information included on the terrain sketch should be organized neatly to avoid clutter and confusion.
c. The terrain sketch is used primarily as a means of analyzing the terrain in an observer's area of responsibility. It helps him determine direction to the target. Once it is constructed, an observer can use the terrain sketch to help him quickly and accurately locate targets by referencing from information already known in his area of responsibility. Also, a well-constructed terrain sketch provides a rapid means of orienting relief personnel. Terrain sketches must be continually refined and updated with data from available fire support planning documents, to include target numbers, final protective fires (FPFs), and fire support coordinating measures.
Figure 3-7. TERRAIN SKETCH
a. Description. The OF fan, GTA 6-7-3 (Figure 3-8), is a transparent protractor that helps the observer identify on the map the terrain he sees on the ground. The OF fan has 17 radial arms that are 100 mils apart and cover a total of 1,600 mils. The OT distance is represented by arcs marked on the radial arms every .500 meters starting at 1,000 and extending to 6,000 meters. Once the observer has determined an OT direction, he can use the OF fan to help him determine an OT distance on the map.
Figure 3-8. OBSERVED FIRE FAN (1:50,000 METERS) (GTA 6-7-3)
b. Preparation. The scale of the OF fan must match the scale of the map. Prepare the OF fan as discussed below.
(1) Place the vertex of the fan over the observer's
(2) Place the center radial in the direction of the center of the observer's area of responsibility.
(3) Move the fan slightly until one of the radial lines is parallel to a grid line. The direction of that radial line is the same cardinal direction as the grid line; for example, a radial line parallel to an east-west grid line, with the OF fan oriented generally east, would be direction 1600.
(4) With a grease pencil, number the radial of known direction. Drop the last two zeros (1600 would be 16). Then label every second radial with the appropriate direction. (Labeling each radial is unnecessary and makes the fan too cluttered.)
|NOTE: Remember that radial lines are 100 mils apart.|
c. Use. Use the OF fan as discussed below.
(1) Look at the terrain the target occupies.
(2) Determine the direction to the target. (Use the compass, the terrain sketch with binoculars, or other means.) (See paragraph 3-7.)
(3) Estimate the distance to the target.
(4) Set off the direction on the OF fan. Plot the OT direction on the OF fan by finding the two radial lines between which the OT direction falls and visually interpolating to determine the target area.
(5) Set off the estimated distance to the target. Look out along this interpolated radial line at the estimated OT distance. This is an estimated target location.
(6) Use terrain association to refine distance. Compare the terrain near the target with the terrain of the estimated target location on the map. If they do not agree, search along the radial line until the terrain and the map match (Figure 3-9).
(7) Determine target location. Use the refined polar plot data or determine the grid from the map.
Figure 3-9. TARGET LOCATION WITH OF FAN
a. When it is necessary to measure angular deviations to determine direction quickly, the observer may use his hand and fingers as a measuring device (Figure 3-10).
b. Each observer should calibrate his hand and fingers to determine the values of the angles for the various combinations of finger and hand positions shown, since finger width and hand size vary for each observer.
c. when using his hand or fingers in measuring angular deviation, the observer should fully extend his arm (lock his elbow) so that his hand and fingers are always the same distance from his eyes. The palm of his hand is always pointed toward the target area.
Figure 3-10. EXAMPLE HAND MEASUREMENT OF ANGULAR DEVIATION
|Join the GlobalSecurity.org mailing list|