FM 30-21

WAR DEPARTMENT FIELD MANUAL

AERIAL PHOTOGRAPHY
MILITARY APPLICATIONS

RESTRICTED. DISSEMINATION OF RESTRICTED MATTER. -- The information contained in restricted documents and the essential characteristics of restricted material may be given to any person known to be in the service of the United States and to persons of undoubted loyalty and discretion who are cooperating in Government work but will not be communicated to the public or to the press except by authorized military public relations agencies. (See also par. 23b, AR 380-5, 15 Mar 1944.)

WAR DEPARTMENT 22 SEPTEMBER 1944

WAR DEPARTMENT FIELD MANUAL
FM 30-21

This manual supersedes FM 1-35, Aerial Photography, 3 December 1942; and FM 30-21, Role of Aerial Photography, 1 November 1940.

RESTRICTED. DlSSEMINATION OF RESTRICTED MATTER. -- The information contained in restricted documents and the essential characteristics of restricted material may be given to any person known to be in the service of the United States and to persons of undoubted loyalty and discretion who are cooperating in Government work, but will not be communicated to the public or to the press except by authorized military public relations agencies. (See also par. 23b, AR 380-5, 15 Mar 1944.)

FM 30-21, Aerial Photography, Military Applications, is published for the information and guidance of all concerned. [A. G. 300.5 (30 Aug 44).]

DISTRIBUTION: As prescribed in paragraph 9a, FM 21-6 except D 1 (10), 2, 7, 17 (5); T of Opns (5); Base C (5); Island C (5); Def C (5); B 1, 2, 5-7, 18 (5), 4, 8, 9, 44 (2); R 1, 2, 5-7, 17, 18 (5), 3, 4, 8-11, 19, 44, 55 (2); Bn 2, 5-7, 17, 18 (2) except I Bn 5 (4),1(5); I Bn 1 (1)2(2); IC 13(1)4(2); IC 55(1), 6(2), 7(3) 8(5)

I Bn 1: T/O & E 1-47; 1-67(1); 21-27; 1-137; 1-167; 1-267; 1-637; 1-757; 1-758; 1-759; 1-767; 1-768; 1-779; Helicopter Sq (2);

IC 1: 3T/O & E 1-747S; 1-749; Combat Camera Unit (1); 41-769; Domestic Photo Unit (2);

IC 5: 5T/O & E 5-500; MA Model Making Team (1), 3Photo Mapping Plat (2), TOA Survey Liaison; 5-59; 5-167; 5-187; 5-188; 5-189 (3 ); 85_96; 5_97; 5-186; 5-466; 5467 (5 ) .

II. Aerial Photographs.
Definitions
Camera types
Vertical photographs
Oblique photographs
Scale
Marginal data
Print paper
Stereoscopic coverage
Reconnaissance strips
Mosaics and photomaps

III. Procurement of Photography.
Responsibility
Theater photography
Procedure for obtaining photography from cooperating air units
Requests for photography
Photography for artillery

IV. Photographic Reconnaissance Operation.
General
Reconnaissance photography
Types of units
Operational considerations for reconnaissance photography
Bomb impact photography
Damage assessment photography
Night photography
Color photography
Infra red photography
Limitations of aerial photography

VI. Utilization of Aerial Photographs.
Photographs and maps in relation to operations
Utilization of photographic production and capabilities
Utilization by ground forces
Utilization by air forces
Utilization by naval and amphibious forces

Vlll. Interpretation of Aerial Photographs.
Mission
Definition
Qualifications of personnel
Coordination with other sources of information
Equipment
Photo interpretation reports
Performance of photo interpretation

This manual supersedes FM 1-35, Aerial Photography, 3 December 1942; and FM 30-21, Role of Aerial Photography, 1 November 1940.

1. PURPOSE. The purpose of this manual is to describe in general terms aerial photography and its application to military operations in modern warfare as it relates to air, ground, and naval forces, and to define the command responsibilities and staff relationships involved in the procurement of aerial photography and information derived therefrom.

2. SCOPE. This manual provides the basic doctrine for the procurement, production, and exploitation of aerial photography. This manual does not cover military applications of aerial motion-picture photography.

3. REFERENCES. Pertinent references regarding tactical and technical information on photography and the several processes pertaining to it include --

TM 5-246, Interpretation of Aerial Photographs. Photographic Interpretation Handbook-U. S. Forces (a reference manual).

U. S. Navy Photographic Interpretation Center technical publications for interpreters.

4. DEFINITIONS. a. An aerial photograph is a picture, either vertical or oblique, taken from an aircraft. The average person is unaccustomed to an aerial viewpoint and therefore the images of familiar objects on aerial photographs appear strange and unassociated with the objects represented. The difficulties presented in interpretation of aerial photography are such that special training in its use is required if the maximum value is to be obtained therefrom.

(1) Intelligence. Aerial photographic information of terrain, activities, or installations.

(2) Mapping and charting. Aerial photographs used in the compilation and correction of topographic and planimetric maps, photomaps, models, aeronautical and hydrographic charts of all types.

(3) Bombardment. Orientation photography of terrain at time of bombing release and bomb impact photography to show location of bomb bursts with respect to target.

5. CAMERA TYPES. Aerial cameras are of two types; reconnaissance and mapping. Mapping cameras are necessarily related to the requirements of the topographic organization (TM 5-240). Reconnaissance cameras include a variety of focal lengths, angles of coverage, and types of shutters in order to provide the classes of photography required.

6. VERTICALS. A vertical aerial photograph is one made with the camera axis vertical or as nearly vertical as practicable in an aircraft. Figure 1 (65K) shows a vertical photograph. The area shown on this photograph is represented within the rectangle in figure 3 (80K). The camera film is practically horizontal at exposure, hence features on the ground are registered on a vertical photograph in perspective with minimum distortion of their horizontal dimensions.

7. OBLIQUES. Oblique aerial photographs are obtained by tilting the optical axis of the camera from the vertical. Figure 2 (70K) is a reproduction of an oblique photograph. This oblique photograph covers an area represented by the trapezoidal section of the map marked on figure 3 (80K).

8. SCALE. Scale is the relationship between a distance on a map or photograph and the actual distance on the ground. This is usually expressed as a ratio called the representative fraction (RF). The scale of a photograph is established by the focal length of the lens used and the altitude of the camera at the time of the exposure.

9. MARGINAL DATA. Certain information will appear on the margin of photographic prints. These marginal data include geographic location, time and date of the photography, and other necessary reference data. Marginal data are prescribed in Army Air Forces Regulation 95-7 and are set forth in Photo Interpretation Handbook -- U. S. Forces. These prescribed data have War Department approval as meeting all Army requirements and must be adhered to.

10. PRINT PAPER. a). Photographs may be printed on either glossy, matte, or semimatte paper of single or double weight. Glossy paper gives clearest definition of detail and is normally used for photo interpretation. The other types are used for special purposes.

b. Print papers with a water-resistant base are for quick work and for production printing. They have a comparatively glossy surface and are suitable for photo interpretation. These papers are not intended for mosaic production.

11. STEREOSCOPIC COVERAGE. When a detailed study of an object is to be undertaken, it is necessary to secure overlapping photographs that may be studied with a stereoscope. Most reconnaissance photography is planned in this manner. Two such overlapping photographs are called a "stereoscopic pair." Mapping photography also requires stereoscopic coverage.

12. RECONNAISSANCE STRIPS. a. A reconnaissance strip is a series of overlapping photographs made from an airplane flying a selected course. Vertical photographs are usually taken in such strips with a minimum overlap of 60 percent of the successive exposures forming the strip.

b. Oblique reconnaissance strip photographs may be made in similar fashion with consistent overlapping when oblique mounts are installed in the aircraft.

13. MOSAICS AND PHOTOMAPS. a. Uncontrolled mosaic. An uncontrolled mosaic is formed by joining several overlapping vertical photographs taken at different camera positions. The term is generally applied to an assembly of one or more vertical strips. When the several photographs are oriented with respect to each other, the result is an "uncontrolled mosaic." This provides a good pictorial representation of the ground, but will have errors in scale and azimuth.

b. Controlled mosaic. When the several photographs are brought to a uniform scale, oriented with respect to one another and fitted to points of ground control, the result is a "controlled mosaic." The accuracy of a controlled mosaic used as a map depends upon the quality of the photography, the character and amount of ground control, and the methods used in its preparation.

c. Photomaps. A reproduction of a photograph or mosaic upon which grid lines, marginal data, and place names are ordinarily added is called a "photomap" and may be reproduced in quantity by photographic or lithographic methods.

14. RESPONSIBILITY. The commanding officer of the using organization is responsible, whether by his own means or by requests of others, for the procurement and distribution of aerial photographs to all subordinate echelons of his command. He is also responsible for establishing procedures relative to the exploitation of aerial photography within his command. In the performance of these duties he is assisted by his intelligence officer and, for air force organizations, by his photographic officer.

15. THEATER PHOTOGRAPHY. The proper use of general aerial photographic facilities of a theater or similar command containing both air and ground elements is a responsibility of the commander thereof. He must take action to establish such priorities as will insure the accomplishment of vital missions and will prevent the diversion of photographic facilities to unrelated or less important operations. In practice, the commander should require the establishment of a "priorities board" or similar agency which will insure proper consideration of all requirements. This agency may be called upon to consider air, ground, naval, joint and combined requirements for general mapping coverage and for intelligence missions. Requests for photography must be submitted through command channels or through such channels as may be approved by the theater commander. Distribution within each command is a responsibility of the commander thereof.

16. PROCEDURE FOR OBTAINING PHOTOGRAPHY FROM COOPERATING AIR UNITS. During an operation in which an air force is cooperating with a ground force, rapid and direct procedure is required. The ground force commander (through designated liaison or other appropriate staff officers) screens and submits his requirements for photography (including priorities) to the commander of the tactical air force or tactical air command for accomplishment. The air commander directs the necessary missions in accordance with the priority furnished, within the limits imposed by the air situation and available equipment. The air commander informs the ground commander of the action taken on requests submitted. The ground force commander should provide ground force photo interpreters at the airdromes of photographic units performing the missions. These interpreters should examine photographs immediately after the printing and select such prints as are desired for quantity reproduction. The air force will furnish the original or duplicate negatives of selected photographs to enable the ground force to produce and distribute such quantities of prints as may be desired. Alternatively, the air force will produce the quantity of prints required within their limitations and deliver same to the headquarters of the ground force commander or his designated representative. Distribution of prints and mosaics within any command is the responsibility of that command.

17. REQUESTS FOR PHOTOGRAPHY. Requests from lower echelons will be made through prescribed channels and will be supported by detailed instructions covering the distribution required, methods of reporting information, priority, date and time deadline. Such requests should specify --

b. Approximate scale. (For obliques, state approximate direction, altitude, and type -- high or low.)

c. Purposes for which photos are intended (any pertinent detail which will materially aid in the satisfactory accomplishment of the mission).

18. PHOTOGRAPHY FOR ARTILLERY. Verticals and gridded obliques for artillery will be taken and especially printed for artillery use. Such photographs will be requested through the unit intelligence officer and requests will conform to the elements of a request as enumerated in paragraph 17.

19. GENERAL. a. The mission of photographic aviation is to secure and produce for military operations of the armed forces --

b. Modern aerial photography is highly specialized. TM 1-220 is a treatise on the problems, technique, and methods of training military personnel in the rudiments of aerial photography. TM 5-240 describes proved methods of producing topographic maps by the use of aerial photographs and stereoscopic plotting instruments. It is sufficient in this manual to observe that the best photography for a specific purpose can be produced only if the primary purpose for which it is intended is made known to those who accomplish the photography, as well as to those who are required to interpret it.

20. RECONNAISSANCE PHOTOGRAPHY. Aerial photographs are one of the most important sources of information available to a commander and when successfully interpreted frequently reveal the most carefully guarded secrets in hostile territory. They reveal enemy transportation and communication systems; port and harbor facilities; industrial installations and activities; air, ground, and naval installations and activities. Such information is of utmost importance to all echelons of command both for planning and execution of operations against the enemy.

21. TYPES OF UNITS. Reconnaissance aviation provides two types of organizations for the initial procurement of aerial photography: photo reconnaissance units and tactical reconnaissance units.

a. Photo reconnaissance units. The photo reconnaissance units operate normally at high altitudes and long range in cooperation with units operating strategically. They are trained and equipped to obtain reconnaissance photography as well as mapping and charting photography. They usually operate unarmed, depending upon speed, altitude, and evasive tactics for protection. In certain theaters, appropriate bombardment type aircraft are employed consistent with the ranges required. These bomber type aircraft may be armed. Photographic reconnaissance aircraft are normally equipped with cameras of 6-, 24-, and 40-inch focal lengths.

b. Tactical reconnaissance units. The tactical reconnaissance units normally operate at extremely low or medium altitudes in cooperation with units operating tactically, and obtain both photographic and visual information to facilitate the proper employment of the tactical air, ground, and amphibious forces. Photographic equipment of tactical reconnaissance units limits them to taking obliques, verticals, and photographic strips of limited areas. Combination visual and photographic tactical reconnaissance missions are customary. A flash report is sent on the visual information with an interpretation report and photographs following. Additional photographic requirements, beyond the capabilities of the tactical reconnaissance units, are requested of the photographic reconnaissance organization.

22. OPERATIONAL CONSIDERATIONS FOR RECONNAISSANCE PHOTOGRAPHY. The employment of photographic and reconnaissance aviation units is set forth in FM 1-20. It should be noted that the success of the photo reconnaissance mission depends to a great extent upon clarity and precision of the request for photography. The problem parallels that of procurement of information by ground patrols and is further complicated by the possibility of mechanical failure, vulnerability incident to the necessity for operation within view of the enemy, and, within limits, weather conditions. In the employment of aerial photography as source of information the following is necessary:

a. Technical requirements of the photography to meet the specific purposes must be defined.

c. When appropriate, prior to the dispatch of a photo reconnaissance mission, a check is made of existing photography to determine to what extent the information or photography is available.

d. If a mission is necessary the following steps must be taken: (1) Priorities for the accomplishment of photographic missions must be established. (2) Aircraft equipped with suitable photographic facilities must be flown over the selected objectives; film must be exposed under conditions that will meet technical photographic requirements; and the aircraft must return to its base. (3) The exposed film must be developed, printed, and interpreted to extract all pertinent information.

23. BOMB IMPACT PHOTOGRAPHY. On most operational bombardment missions, a certain number of bomber aircraft are equipped with cameras which expose film during the bombing missions. This photography normally shows point of bomb release and is useful in developing bomb impact plots. Under certain conditions, it is possible to accredit particular bomb bursts to individual aircraft. The principal value of bomb impact photography is the immediate indication of the success of the mission. As detail of the target is obscured by smoke from bomb explosions, bomb impact photography is not satisfactory for bomb damage assessment. Its chief use is for operational studies.

24. DAMAGE ASSESSMENT PHOTOGRAPHY. As soon as practicable, reconnaissance is dispatched to procure photography to be used in the assessment of damage. This photography is normally accomplished by reconnaissance aircraft. Similarly, in tactical reconnaissance, photography is accomplished for the same purpose after artillery bombardment. Damage assessment determines the point beyond which further bombardment is no longer necessary, and permits an estimate of the probable damage that will be caused by similar missions against similar targets. It is also useful in long range intelligence to determine enemy capabilities.

25. NIGHT PHOTOGRAPHY. a. Night photography is accomplished with special cameras using light from high intensity flash bombs or other sources. Proper appreciation of night photography should be based on the special technical problems involved:

(1) The candlepower of the light source limits the area which may be illuminated.

(2) The number of photographs that may be made on any individual mission will depend upon the type of light source used.

(1) Reconnaissance. The detection of the night activities of the enemy such as movement of troops, batteries, shipping, and supplies.

(2) Bombardment. Photographs from individual aircraft establish the exact position of the attack when compared with daylight reconnaissance photographs or accurate maps of the area under attack. All of the photographs taken by the various aircraft of the mission when studied together indicate the over-all effect of the mission.

26. COLOR PHOTOGRAPHY. Aerial color photography has recently reached a stage of development where it may be of practical operational value. It has been of some value for the study of offshore and beach conditions and in the detection and interpretation of camouflaged or otherwise concealed installations. The limiting factors associated with the use of aerial color photography include the necessity of viewing transparencies and the difficulties incident to reproduction.

27. INFRA RED PHOTOGRAPHY. Infra red photography is taken on special film and has very limited application in theaters of operation. It may be of value in camouflage detection of installations concealed with ordinary paints or dyed cloth or imitative vegetation.

28. LIMITATIONS OF AERIAL PHOTOGRAPHY. a. The uses to which aerial photographs may be put depend upon the technical quality of the photograph. This quality in turn is dependent upon the following:

b. The processes of photography all require time for their accomplishment. Time is required for each of the several steps of processing negatives and prints and interpretation of photos, as well as for the mechanics of preparing for, performance of, and return from the aerial mission. The requester, the airdrome, and the photographic laboratory and interpretation section may be separated by such distances as will involve a considerable expenditure of time. This time factor must be considered by all who request aerial photographs.

c. Successful interpretation depends upon the skill and experiences of the individual interpreter, the reference material available to him, the quality of the photographs, the scale of the photographs, and the time available for interpretation. In general the better the quality of the photograph, the smaller the scale at which a specific type of installation can be accurately interpreted. Detailed interpretation calls for a scale as large as possible consistent with the equipment available and safety of flight. Mapping and general preliminary planning can be done with photographs of smaller scale.

29. DESCRIPTION. Mapping or charting photography implies the systematic photographic coverage of terrain basically necessary for military operations. In modern war, it allows armies to fight over terrain with a reasonable knowledge of terrain features, a knowledge formerly obtainable only by tremendous efforts over long periods of time. It is the photography which --

e. Provides artillery and others with terrain data which it is impossible to draft on maps.

f. Provides general terrain coverage which, in the form of mosaics, is more satisfactory for many staff purposes than maps.

30. REQUIREMENT. Mapping or charting photography should be planned and executed over prospective areas of operation at the earliest practicable date consistent with available photographic facilities and the general operational plan. Failure to provide this type of photography and substitution of piecemeal photo reconnaissance effort not only deprives all forces of adequate maps or charts but is wasteful of total photographic effort. The proper consideration of this requirement and the presentation of a plan for command decision is a function of the various intelligence and operations staff officers.

31. MAPPING RESPONSIBILITY. a. Aerial photography for mapping is primarily a command responsibility with execution charged in appropriate echelons (AR 300-15) as follows:

(1) The Assistant Chief of Staff, G-2, prepares plans and policies and supervises.

(2) Engineers prepare specifications and priorities for the aerial photography required.

b. In practice, liaison between the topographic engineers and the aerial photographic organization must be established at working levels. In the interest of efficiency and economy of effort by all concerned, it is important that the photography attain a high degree of mechanical perfection. The engineer must be familiar with equipment limitations and operational conditions so that the specifications and priorities he recommends will not be impossible of accomplishment.

32. RESPONSIBILITY FOR CHARTING. Air forces are responsible for all phases of aeronautical charting, hence staff action in commands comprised of both ground and air forces is limited to coordination of the mapping and charting efforts. Aside from this coordination, the air force commander is responsible for planning, supervising, and executing the required photography.

33. MAPPING AND CHARTING SQUADRONS. a. These units are specifically trained and equipped for performing the mapping and charting missions. Mapping and charting squadrons are mentioned together herein since their missions are similar and training identical. Mapping photography generally pertains to vertical photographic coverages for the production of large-scale maps. Where medium and small scales only are required, mapping photography may be identical or similar to that required for charting. Charting photography generally pertains to trimetrogon coverage for small-scale charts. It also applies to that required for certain large-scale charts. Both maps and charts require large-scale photography for identification of detail in certain cases.

b. Photo reconnaissance units are trained for the performance of mapping photography in addition to reconnaissance. They perform the mapping mission when mapping squadrons are not available or to supplement their work, particularly over heavily defended areas.

c. Mapping and charting photography is limited by ranges of available aircraft, camera installations, enemy action, or weather.

34. PHOTOGRAPHS AND MAPS IN RELATION TO OPERATIONS. a. Intelligent planning and operations require the best map information obtainable and all the intelligence securable from aerial photography. Aerial photography has proved to be a superior source of objective information.

b. If adequate maps and charts are to be prepared of any theater prior to offensive operations, mapping or charting photography must precede such operations by a sufficient length of time, consistent with local weather factors, to allow for photographic coverage, processing, compilation, reproduction, and distribution.

c. Reconnaissance and photographic requirements necessitate continuing photography prior to and throughout the period of operations in order to keep existing information current.

35. UTILIZATION OF PHOTOGRAPHIC PRODUCTION AND CAPABILITIES. In order to obtain more than a small fraction of the information of which aerial photography is capable, intelligence coordination and direction are required. An understanding of the mission, possibilities, and problems incident to the establishment of priorities for photography is necessary by all elements of the command.

(1) Photographic coverage is used directly by ground forces in the following forms:

(2) Photography is also used in the preparation of maps, sketches, models, diagrams, firing data, etc.

b. Long-range uses. (1) The principal long-range use of photography is in the preparation of maps for prospective operations. Whether new maps are compiled or existing maps are revised, systematic mapping photography is used.

(2) Other long-range uses are in connection with special terrain studies or other intelligence purposes prior to operations. These involve beaches, water supply, possible airfield sites, enemy defenses, roads, railroads, routes of approach, bridges, streams, terrain in general, and vegetation.

c. Tactical uses. During combat, aerial photography used by various ground elements as outlined below.

(5) Transportation units. (a) Determination of most suitable transportation for operational areas.

(6) Military intelligence specialists' teams or other specialists. (a) Fixing locations of defenses and concentrations revealed by P/W's or friendly aliens.

d. Photo interpreter teams. Military intelligence photo interpreter teams, attached to division and higher headquarters, are equipped and trained to carry out any of the above-mentioned procedures.

37. UTILIZATION BY AIR FORCES. a. Photographic aviation commander. The photographic aviation commander will generally be the best qualified and logical officer to serve as photographic officer on the staff of the air force commander. As such he will be charged with advising the commander on mapping and photographic matters, coordinating photographic operations, and advising on all photographic activities. Under the direction of the air force commander, he will --

(1) Coordinate and direct photographic aviation and photographic efforts of other aviation to insure most efficient functioning.

(2) Coordinate and direct laboratory, interpretation, compilation, and reproduction operations to insure that all information in the form of exposed film is converted to photographic information and is furnished to the using agencies.

b. Uses of photography within an air force. (1) General intelligence. To maintain a reliable and current picture of enemy activity and to test and support the accuracy of all types of information received from prisoners of war interrogation, refugees, and all other sources.

(2) Planning. Reconnaissance photography is used extensively in the selection of air targets and the establishment of priorities for operations.

(3) Analysis of enemy defenses. The following types of information regarding enemy defenses are prepared largely from reconnaissance photography --

(a) Flak charts showing current positions and effective range of antiaircraft batteries.

(b) Location and range of enemy radar and other detection devices including searchlights.

(4) Briefing. Aerial photography is used widely in briefing prior to operations and interrogation of returned air crews in the following forms --

(b) Small scale photos, verticals, and obliques, clarifying routes, check points, initial points and emphasizing landmarks.

(S) Assessment of damage. The assessment of bomb damage and determination of future operations and tactics against the same or similar targets is based on reconnaissance photography.

38. UTILIZATION BY NAVAL AND AMPHIBIOUS FORCES. Aerial photographs are useful to naval and amphibious forces in preparing maps and charts of all types. The following are illustrative uses --

a. Navigational charts. ( 1 ) Accurate location of shorelines by radial line plotting of overlapping photographs.

(2) Location of navigational hazards, such as reefs, sunken ships, underwater barricades, minefields, nets and booms, etc.

(a) Water depths up to 2 or 3 fathoms can be estimated 24 to the nearest 2 feet from suitable photos. This makes navigation close to shore less hazardous.

(b) Position of enemy mine fields in harbors can be estimated, even though mine fields are not visible on photos, by noting channel rigidly followed by ships as shown on successive photo coverages.

(c) Location of prominent headlands and other topographic features as an aid to piloting. These are usually indicated by form lines on the chart. Supplementary oblique sketches or photos showing these prominent features are useful to PT boats and assault craft as well as larger vessels.

b. Naval bombardment charts. (1) Identification of enemy guns, supply dumps, pillboxes, and other targets for naval bombardments.

(2) Accurate location of these targets through construction of a gridded controlled mosaic (map or chart) of the bombardment area. Mutual support by air and surface units is in this way facilitated as each can advise the other during the bombardment as to the grid positions of targets not yet neutralized.

c. Maps for shore use by amphibious troops. Such maps emphasize points of particular concern to amphibious troops including --

d. Other naval or amphibious uses. (1) Models are useful in briefing amphibious troops and supporting air units. Their quality, both as to accuracy of scale and delineation, depends upon the ground control available and the quality of the photographs used.

(2) Damage to enemy targets by air or surface bombardment is assessed by comparison of sorties taken before and after attack. From such studies, the most effective means of destroying or damaging any given type of target may be ascertained. Damage assessment also is of value in planning the occupation of an area.

(b) Determination of speed from photographs of the wakes of ships, thus facilitating interception.

(a) Determination of suitable harbors, anchorages, sites for camps and airfields, etc., by preliminary reconnaissance.

(b) Determination of the effectiveness of our own camouflage and other security measures by subsequent reconnaissance.

39. TYPES OF LABORATORIES. Laboratories may be either fixed, mobile, portable, or improvised.

a. A fixed photographic laboratory is one housed in a building designed for that purpose with permanently installed equipment. Fixed laboratories are commonly used in rear areas and aboard ships.

b. A mobile photographic laboratory may be installed in a truck, trailer, or other mobile unit.

(1) Specially designed and fitted photographic laboratory building so constructed that it may be knocked down and packed compactly for movement or shipment.

(2) Specially designed photographic laboratory dark tents with necessary special equipment which can be transported by air.

d. Darkrooms may be improvised or constructed in any type of building or cellar capable of being made light tight and in which the necessary utilities may be installed.

40. UTILITIES. The fundamental requirements for a photographic laboratory other than technical equipment are electricity and water.

a. Electricity may be provided by small gasoline generator units. However, where possible, full utilization is made of locally available electric power supply.

b. Water may be procured by pumping from a stream or other source, by transporting in tank trucks, or by attachment to a public water system. Water should always be tested for its suitability for photographic processing before use.

41. PHYSICAL LOCATION. In deciding upon the physical location of the photographic laboratory, many variables must be considered in addition to the usual consideration of concealment. It is highly desirable to locate the laboratory as close to the flying line as is consistent with security, water and power supply. The actual transportation of exposed film to the laboratory after a mission has been flown introduces a time element worthy of the highest consideration. It is desirable that the photo interpreters be placed in close proximity to the photographic laboratory.

42. PROCEDURES. a. Each laboratory usually requires two or more small darkrooms for the development and fixation of aerial film. The laboratory is informed by the organization performing the photography when film from photographic missions may be expected in order to facilitate the processing of the photography.

b. When engaged in mapping and charting one quick print for study by the unit that compiles the map or chart will be produced immediately from each negative. Additional prints will be made as required. When requested by the mapping agency, the original mapping negatives will be loaned for the period required by that agency.

c. All laboratories can produce a limited number of prints for the use of photo interpreters. Quantity production of reconnaissance photographs for distribution is accomplished at certain larger laboratories of the air forces and by topographic units of the ground forces.

d. Negatives are properly titled for filing and suitable plots or indices are prepared showing the area covered. Mobile laboratories do not have sufficient filing space for storage of other than current negatives. Arrangements must be made for the periodic transfer to rear area laboratories for file. Photographic laboratories file negatives in such a manner that they may be readily located.

43. MISSION. The mission of photographic interpretation units or personnel in a theater of operations is to perform strategic or tactical interpretation of aerial photography and to disseminate the resulting information for collation and evaluation with intelligence from other sources.

44. DEFINITION. a. Interpretation of aerial photography is the process of determining the identity and physical characteristics of features of terrain, works of man, and the nature and extent of ground, sea, or air activity. Applied to military purposes, this process is limited to the extraction of that information which pertains to terrain and to the capabilities, installations, strength, dispositions, and activities of the enemy relating to his war effort. Briefly stated photo interpretation is --

b. Interpretation of aerial photographs involves special technique. It requires a suitable background of experience, technical ability, and training in the procedures involved. In order that the interpretation be correct, it is essential that the detail examined be properly understood by the interpreter and that all reliable information from other sources be accessible and utilized.

45. QUALIFICATIONS. a. The physical qualifications for personnel who perform interpretation of aerial photographs include good eyesight. Persons subject to eyestrain have difficulty maintaining the tempo of work required in the field. Any marked defects of vision jeopardize recognition of the minute detail recorded on photographs and may prevent three dimensional or stereo-vision -- a necessity to the interpreter.

b. Persons especially useful in obtaining over-all military information through the interpretation of aerial photographs are those who have had varied and broad experience. Professional background in operation or design of large industrial or transport installations, employment of military and naval equipment, field geology, architecture, and city planning are particularly useful.

c. Trained interpreters should be able to determine photo scales, read and interpret maps, use stereoscopes, scales, and other instruments used in the interpretation of photographs; perform drafting and photo plotting; and lay uncontrolled mosaics. General interpreters and particularly those of the air forces are trained to identify military equipment, aircraft, merchant and naval vessels; perform required interpretation of terrain, airdromes, Army installations, shipyards, harbor facilities, railroad yards, communications, shipping and industrial plants; analyze camouflage and assess bomb damage.

d. Interpreters assigned or attached to ground forces are trained in evaluation of terrain from a military viewpoint, in general and specific identification of military units, and in certain mechanical and technical procedures applicable to the use of aerial photography. The functions of these interpreters are those pertinent to the unit to which they belong and therefore are not as broad or varied as the interpretations required by air forces and higher headquarters.

46. COORDINATION WITH OTHER SOURCES OF INFORMATION. a. Since photo interpretation is a reliable and prolific source of information, coordination with all pertinent intelligence agencies is necessary. The appropriate intelligence officer should continually make available such reliable information as will aid the interpreter. Items such as maps, hydrographic charts, city plans, tourist guides, etc., are essential to interpreters.

b. Photo interpreters may be called upon to verify or refute information secured from interrogation of prisoners of war, friendly aliens and air crews, radio intercepts, and other intelligence sources.

47. EQUIPMENT. There are two types of interpreter kits (AAF Technical Orders, 00-30 series). The organization kit includes a table suitable for limited drafting and for examining negatives by transmitted light as well as certain drafting equipment and materials. The individual's kit contains necessary instruments and an initial supply of certain expendable items. Although it is advisable to equip each photo interpreter with the individual's kit, a limited amount of interpretation is possible with a minimum of equipment (pocket type stereoscope and an accurate scale).

48. PHOTO INTERPRETATION REPORTS. a. The result of a study of aerial photographs is presented as an interpretation report. This report may be verbal or written and may include or consist of an annotated map, diagram, graph, or chart. Depending upon the time involved in their preparation and the detail presented, reports may be classified as immediate or detailed.

b. Immediate reports are completed and forwarded in a minimum of time after the photography has been received. Such reports briefly answer specific questions applicable to immediate operations concerning objectives photographed.

c. Detailed reports are usually based upon comparative studies of photography taken over a period of time and may involve many hours of research upon the part of the interpreter. There are three types of detailed reports: routine, periodic, and special.

(1) Routine reports are usually issued after every mission and supplement immediate reports previously dispatched. Other routine reports are prepared that are restricted to a single field of information. Examples of such fields are defenses, shipping, damage assessment, etc. Several different reports may be prepared from the same group of photographs of an objective.

(2) Periodic reports are issued at regular Intervals and cover specific activities. Examples of these are: daily flak reports which contain information about the physical condition of the installation and the location of new batteries observed on the day's photography; weekly transportation reports which cover the conditions at critical railroad facilities and ports and harbors; monthly aircraft production reports which present the evidence from photographs relative to the activity at aircraft factories covered by reconnaissance.

(3) Special reports are issued at irregular intervals and cover any topic capable of being interpreted from photographs. Examples of these are new types of aircraft observed on photographs; construction details of enemy installations; details of refitted naval vessels; terrain studies for various purposes; studies of industrial plants.

d. Detailed reports as listed above pertain principally to air forces and higher headquarters. Reports from interpreters with ground units may generally be classed as immediate reports.

49. PERFORMANCE OF PHOTO INTERPRETATION. a. Photo interpretation is performed for ground forces by specially trained ground force teams attached to division or higher headquarters or by personnel organic to ground units. Under certain conditions, interpretation teams or individuals operate with the tactical reconnaissance squadrons as well as with their own units.

b. Photo interpretation is performed in the air forces by units of specially trained personnel in the reconnaissance squadrons and in photo technical units which are usually adjacent to air force headquarters. Long-range strategic photo interpretation is also performed by interpreters under the supervision of the AC/AS Intelligence at Headquarters, Army Air Forces.

c. Photo interpretation is performed in the Navy by specially trained naval officers attached to theater commanders, naval task forces, and by photo interpretation squadrons operating with naval photo reconnaissance squadrons. The Photographic Interpretation Center, operating under the Chief of Naval Operations, provides facilities for fulfilling special photo interpretation needs of the Navy.

d. In some theaters, the interpretation personnel of the higher echelons of all armed forces are merged into a single joint interpretation unit under a common command.

e. Immediate reports are normally prepared by photo interpretation personnel located at a base from which reconnaissance aircraft operate. Detailed reports are normally prepared by the photo interpreters at photo reconnaissance headquarters or in a joint interpretation unit. Under certain conditions, such as in an extended theater, detailed reports may be prepared by interpreters at an advance operating base.

f. Bomb impact plots prepared from photography accomplished during actual bombing and strafing missions may be prepared by photo interpreters in the bombardment organizations or by interpreters at photo technical organizations.

50. DEFINITION. Photogrammetry is the science of determining measurements from photography, but the name is more commonly applied to the science of determining some type of map information from aerial photographs. Some photogrammetrical method must be utilized in order to extract the inherent topographic information from an aerial photograph. The subject is adequately covered in TM 5-240 in connection with mapping and is mentioned herein only as an integral part of the military application of aerial photography.

51. EMPLOYMENT. There is a number of factors which must be considered in determining photogrammetrical methods to be used --

a. The purpose for which the resultant photogrammetric product is prepared is of prime importance in determining the method and accuracy required.

b. The type of photography available, oblique, vertical, trimetrogon, may determine the general photogrammetric process. The quality of the photography including both pictorial physical properties will affect the results obtained.

d. The photographic and photogrammetric equipment available at the location where the work is to be performed will be a limiting factor.

e. The personnel available, their type of training, experience, and skill, will have a direct bearing on the results obtained and the time required.

f. In general, the more precise forms of photogrammetric compilation of a long-range planning nature will be performed in rear areas where personnel and precision equipment are not affected by combat conditions.

g. In combat areas, less precise methods are more applicable to the immediate nature of the work required and to field conditions.

52. PHOTOGRAMMETRIC PRODUCTS. a. A convenient general classification of photogrammetric products is as follows --

(1) Those retaining the original photographic detail in the final product, such as photomaps.

(2) Those in which the final product uses conventionalized signs and symbols, such as maps.

b. Class (1) has the advantages of retaining the infinite detail of the photograph and conserving drafting work. It includes mosaics of all types, single photographs used as photomaps, photo print assemblies used as indices, etc.

c. Class (2) has the advantages of clarity and emphasis. It includes sketches, diagrams, map manuscript, and maps and charts of all types.