Observation Techniques
This appendix is an overview of observation techniques and equipment. The last part of this appendix deals with tactical uses of night vision devices (NVDs) and training tips. Although the prime reference is night operations, the material also applies to limited visibility operations (fog, rain, snow, and sandstorms).
An observer's capability to detect aircraft increases as the size of the search sector assigned decreases. Detection is more likely if an observer is assigned responsibility for searching a narrow sector than if he is responsible for searching the entire area surrounding his position. If an alert warning system is supporting the observer, he may be assigned a fairly large sector (for example, 90 degrees) for general surveillance. When a warning is received, he then narrows his search sector (for example, to 30 degrees) and centers it on the aircraft's approach azimuth. Decreasing the sector size to less than 30 degrees is not advisable because the alert warning system azimuth data may not be accurate. An error of only a few degrees may cause the observer to miss an aircraft. Often observers, using the horizon as a reference, tend to concentrate their search near the horizon and disregard objects high above the horizon. Therefore, when assigning search sectors, the sector should be defined in both horizontal and vertical planes (see the illustration below).
A simple way to estimate how high above the horizon to search is to use the hand. Facing the primary target line (PTL), extend either the left or right arm fully and extend the fingers. The tips of the thumb and little finger should form a line perpendicular to the ground. Now, when the little finger is touching the horizon, the tip of the thumb is approximately 20 degrees above the horizon (see the illustration below). The observer should frequently focus his eyes on a distant object, such as a cloud or terrain feature (otherwise, the eyes tend to relax and distant objects become blurred). Search the area near the sun by extending arm and hand to block out the sun's glare. Looking into the sun without shielding the eyes will cause them to become blinded for a few seconds. This may cause the observer to lose sight of the target. The observer should squint his eyes if he has trouble focusing at long ranges. Squinting compresses the eyeballs, thus changing their focal length and making distant objects come into focus. The observer should keep his eyes on the aircraft once he sees it. If he has to look away from it, he notes the direction of the aircraft and moves his eyes away from it when the aircraft is near some object, such as a cloud or a terrain feature, that will guide his eyes back to it. Observers may use one of two systematic methods of search to look for aircraft in any type of terrain. In the first method, the observer searches the horizon to about 20 degrees (356 mils) above the horizon by moving his eyes in short movements across the sky, working his way up and across. He continues the scan pattern to below the horizon to detect aircraft flying nap-of the-earth (see the Horizontal Scanning illustration). In the second method, the observer searches the sky using the horizon as a starting point and prominent terrain features as points of reference. He moves his eyes in short movements up the sky, then back down, continuing this movement across the terrain. He scans in the same pattern below the horizon to detect aircraft flying NOE (see the Vertical Scanning illustration). Observers with more experience and above average visual acuity may use nonsystematic methods of search that work best for themselves such as--
- Combination of the two systematic methods.
- Search of the horizon in the shape of an oval to about 20 degrees above the horizon.
- General and random search of the horizon.
When the sensor section occupies a tactical position, each section member will lake turns searching for aerial targets. This allows one member to search while his partner rests his eyes and provides ground security. Search sectors are arranged to provide all-around coverage of the entire area and overlapping coverage of the assigned sector of search on likely approach routes. When aircraft are detected, section members shift primary search emphasis to the azimuth of approach (with frequent all-around scans) and send the appropriate reports. At times, the sensor section will be assigned a sector of responsibility by the sensor section chief or the supported unit commander.
A map reconnaissance of the supported unit's direction of movement or area of operation will help to pinpoint areas from which aircraft are most likely to attack the unit. Mark the far sides of wood lines, ridge lines, and significant folds in the terrain out to at least 3,000 to 5,000 meters. This is where attack helicopters can lie in wait at the maximum range of their antitank guided missiles (ATGMs). Mark restricting terrain, defiles, and narrow valleys where the maneuver unit may be forced to pinch together, becoming lucrative targets for air attack.
Many aircraft have tell-tale signatures which can
lead to early detection. Sensor sections should look for
the following:
- Sun reflection from aircraft canopies or cockpit windows.
- Blade flash from rotating helicopter blades.
- Smoke or vapor trails from jet aircraft and missiles or rockets fired from aircraft.
- Dust or excessive movement of tree tips and bushes in a particular area.
- Noise from helicopter blades or from jets breaking the sound barrier.
Observation at night and in low-light conditions differs greatly from the observation techniques used during daylight hours. The following paragraphs discuss the impact of night and low-light conditions on the ADA sensor section.
The ADA sensor section's isolation may lead to a feeling of impending peril. The section member imagines dangers and may panic under sudden stress. He has a tendency to doubt the unknown. The unseen enemy increases his fear at night. Isolation reduces combat efficiency. During night or limited visibility conditions, isolation is intensified. Even small distances between individuals are exaggerated at night. The ability to function and fight at night is directly related to individual skills, unit teamwork, and confidence in leaders. Confidence is built through practice and unit cohesiveness. Skill, will, and teamwork develop sections which can operate effectively at night.
Just as the night affects the mind, it also affects the senses of sight, hearing, and smell. Maximizing the capabilities of the senses enhances the ability to fight at night. Improving the senses of hearing and smelling requires training; vision is maximized by understanding how the eye operates at night and how to efficiently use its capabilities.
The eye's vision at night is different from daytime vision. At night, it sees with spiral eye cells called rods. Rods cannot differentiate color and are easily blinded when exposed to light. This creates a central blind spot which causes larger and larger objects to be missed as distances increase (see the Central Vision--Night Blind Spot illustration).
While working and performing tasks in daylight, the exposure to light directly affects night vision, and repeated exposure to bright sunlight has an increasingly adverse effect on dark adaptation. Exposure to intense sunlight for two to five hours causes a definite decrease in visual sensitivity which can persist for as long as five hours. This effect can be intensified by reflective surfaces such as sand and snow. At the same time, the rate of dark adaptation and degree of night vision capability will be decreased. Since these effects are cumulative and may persist for several days, military neutral density (N-15) sunglasses or equivalent filter lenses should be used in bright sunlight when night operations are anticipated.
Dark adaptation or "night vision" is only the first step toward maximizing the ability to see at night. Night vision scanning can enable soldiers to overcome many of the physiological limitations of their eyes and can reduce the visual illusions that so often confuse the observers. The technique involves scanning from right to left or left to right using a slow, regular scanning movement (see the Typical Scanning Patterns illustration). Although both day and night searches employ scanning movements, at night it is essential to avoid looking directly at a faintly visible object when trying to confirm its presence.
Viewing an object using central vision during daylight poses no limitation, but this technique is ineffective at night. This is due to the night blind spot that exists during periods of low illumination. To compensate for this limitation, soldiers are taught to use off-center vision. This technique requires that an object is viewed by looking 10 degrees above, below, or to either side of it, rather than directly at the object. This allows the peripheral vision to maintain contact with an object (see the following illustration).
Even when off-center viewing is practiced, the image of an object viewed longer than two to three seconds tends to bleach out and become one solid tone. As a result, the object is no longer visible and can produce a potentially unsafe operating condition. To overcome this limitation, the soldier must be aware of the phenomenon and avoid looking at an object longer than two to three seconds. By shifting his eyes from one off-center point to another, he can continue to pick up the object in his peripheral field of vision.
Visual sharpness is significantly reduced at night; consequently, objects must be identified by their shape or silhouette. Familiarity with the architectural design of structures common to the area of operations will determine one's success using this technique. For example, the silhouette of a building with a high roof and a steeple can be recognized in the United States as a church, while churches in other parts of the world may have entirely different shapes.
The following illustration shows distances at which light sources can be seen at night with the naked eye. For observation from the air or high ground, these distances are increased two to three times.
SOURCE DISTANCE
Vehicle headlights .............................. 4 to 8 kilometers
Muzzle flashes from single cannons ..... 4 to 5 kilometers
Muzzle flashes from small arms .......... 1.5 to 3 kilometers
Bonfire .............................................. 6 to 8 kilometers
Flashlight ........................................... up to 2 kilometers
Lighted match .................................... up to 1.5 kilometers
Lighted cigarette ................................. 0.5 to 0.8 kilometers
The soldier's hearing becomes more acute at night. Several factors contribute to this: increased concentration; sound travels farther in colder, moist air; and there is less background noise. Practice and training help overcome a soldier's lack of confidence in what he hears at night. Training enables him to discriminate multiple sounds, faint sounds, and sound-source directions. The Hearing Distances illustration shows the distances at which sounds are audible at night in open areas.
SOURCE DISTANCE
Cannon shot .................................... up to 15 kilometers
Single shot from a rifle ...................... 2 to 3 kilometers
Automatic weapon fire ..................... 3 to 4 kilometers
Tank movement:
. .On a dirt road ............................... up to 1.2 kilometers
. .On a highway ................................ 3 to 4 kilometers
Motor vehicle movement:
. .On a dirt road ............................... up to 500 meters
. .On a highway ................................ up to 1 kilometer
Movement of troops on foot:
. .On a dirt road ............................... up to 300 meters
. .On a highway ................................ up to 600 meters
Small arms loading ............................ up to 500 meters
Metal on metal .................................. up to 300 meters
Conversation of a few men ................ up to 300 meters
Steps of a single man ......................... up to 40 meters
Axe blow, sound of a saw ................. up to 500 meters
Blows of shovels and pickaxes .......... up to 1,000 meters
Screams ............................................ up to 1,500 meters
Oars on water ................................... up to 2,000 meters
Smell is the soldier's most unused sense. Only about two percent of its potential is used. The enemy's diet usually varies from that of US soldiers. Different diets produce different characteristic human odors. People who eat a meat diet have a different odor from those who eat a vegetarian diet. Once a soldier is accustomed to the enemy's characteristic odor, it is easy to detect and differentiate at night. Practice improves skill and confidence. Sensing odors at night can be improved by facing into the wind at a 45-degree angle. Relax, breathe normally, take sharp sniffs, think about specific odors, and concentrate. The Smelling Distances illustration shows distances at which some odors are detectable at night.
SOURCE DISTANCE
Diesel fuel ................................. up to 500 meters
Single shot from a rifle ............... up to 150 meters
Heat tab .................................... up to 300 meters
Training is the cornerstone for success in battle. The importance of training all personnel to a high proficiency for night combat, both with and without NVDs, cannot be overemphasized. The philosophy for training in the use of night vision devices is underpinned by realistic, sustained, multiechelon training focused on the mission. To sustain the soldier's skill in using NVDs, the leader must train them often enough to prevent skill decay. All training for night operations need not be conducted at night. For example, knowledge of SOPs, combat drills, and operation of thermal imagery devices can be done during daylight. This training enhances proficiency in executing these techniques at night. "Turning off the light" in training can be accomplished in several ways. Manual soldier skills can be executed by blindfolding soldiers during assembly and disassembly of equipment tasks. The M1944 goggles, with darkened lenses, may be used during daylight training. NVD operators must be rotated during training; relief operators must be trained to the same proficiency level as the primary operators. TOE levels of NVDs can be supplemented by loan items from supported units to make maximum use of- available training time. Training with NVDs should, as a minimum, include equipment adjustment, maintenance, employment, and target recognition. Developing unit and individual proficiency in using and employing night operations equipment is necessary prior to starting night tactical training. NVDs c contained in the current battery TOEs are described in the Night Vision Devices illustration on page B-8.
REMOTE SENSORS
Remote sensors (REMS) are among the newer items added to the reconnaissance, intelligence, surveillance, and target acquisition (RISTA) family of equipment. They are used extensively on surveillance missions; however, their ability to electronically locate a target makes them vulnerable to enemy target acquisition devices. Current force structure for light infantry calls for intelligence and surveillance to be the responsibility of MI battalions. The one exception is the use of the platoon early warning system (PEWS) which will replace the patrol seismatic intrusive device (PSID) as the battery level sensor. REMS provide information for target acquisition, intelligence, and alert or early warning, depending upon the unit mission. REMS can be used to provide flank security, rear area security, and security for critical installations; to monitor objective areas or LZ/DZs; to fill gaps between units; and to protect lines of communications. Operational planning should also consider employment of REMS for effective use in a stay-behind, surveillance role during retrograde operations, or to monitor enemy advance and deployment during withdrawal movements. REMS can detect the presence of personnel or vehicles; however, these systems cannot discriminate between types of vehicles or between friendly or enemy units. For this reason, NVDs must be used in combination with sensors. Binoculars, direct fire scopes, or any image-magnifying optical equipment also enhances night missions and night operations.
The PEWS is a lightweight, self-powered, portable intrusion detection system designed for small units. The sensors are emplaced (unattended) in forward combat zones. Sensors are of two types, each of which consists of a combination of detectors. The number of each type of sensor to be employed in a PEWS set varies and depends upon specific mission requirements. There are nine sensors in a PEWS set. These sensors can operate in a radio-link or wire-link mode (see the following illustration). No single NVD or method of employment is a guaranteed solution for the sensor sections to use to conduct successful night operations. Extensive equipment familiarization and training, incorporated into tactical operations, are essential for mission success.
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