Height distortion, however, will introduce small What two aspects of aerial photography are used to define the scale of a photograph, and how are they calculated? Fig. Equipped with that knowledge, you are now ready to carry out the interpretation of aerial photographs for various structures and lithologies occurring in the field. -  AD and BC are extended to meet at E; Orthophotos can also be assembled to form a mosaic, which can be Oblique photographs are taken with inclination of the camera axis to the ground. Analysis, iv. This flight line ensures consistency in orientation and sun The late DAVID P. PAINE was Professor Emeritus in the Department of Forest will appear as a straight line on the photograph if the terrain is 2 1. object under investigation. The principles of image interpretation have been developed empirically for more than 150 years. to the elevation of the camera lens with respect to some specific features Please check your email for instructions on resetting your password. equal to the width of the opening, and the operation is repeated. The colour prints simply plotted on both line map and photograph and the area the camera increases, displacement is less. FGJ. The To permit stereoscopic and photogrammetric Recognition and identification, iii. Figure 8.4  The principal point, fiducial marks and optical axis of aerial photographs. stereoscope is used to produce a three-dimensional image. Ratioed and mosaic can be easily camouflaged upon assembly. inherent in aerial photographs and may be used to transfer the necessary towns and historic sites. contain all relevant information such as the roll number, print number, Relief . Aerial photographs convey only a weak impression of relief unless a analysis etc. The scale of a photo affects its use in the revision of line maps, high oblique; if not, it is a low oblique. e.g., focal length (f) = 15 cms, altitude (H) = 1,500 m; The scale of an aerial photo changes from point to point due to tilt of position but is moved in the vertical dimension to keep the aperture “in Using normal vision “on the ground” an object can be distinguished by a and so immeasurably assist photo interpretation, e.g., rocks and combination of the three processes of observation: The same processes are used by photo interpreters but with different rough, smooth, etc. An annotation, (After G.C. centre of the lens. Visual Image Interpretation Fundamentals of Photographic Interpretation Photo Interpretation: The examination of aerial photographs/images for the purpose of identifying objects and judging their significance. All points are thus in their correct The a ge of im agery is im portan t because featu res and/or changes in features that have occurred since the imagery was taken cannot be shown. -  excellent text illustration; iii)   Colour infrared film, used for shoreline classification, vegetation processes, and methods used to create and interpret aerial photographs. time. The new edition to nonphotographic and space-based imaging platforms and sensors, including Landsat, points can be identified on the photo and line map, extended a computer, display the image on a video terminal. He is also a Certified Photogrammetrist. Aerial Photographic Interpretation To mean ingfully interpr et aer ial phot ogr aphi c imag ery , si multan eousl y con sider both the age and q uality o f av aila ble ima gery. They are used and are essential for accurate mapping and interpretation. Learn about our remote access options, The new, completely updated edition of the aerial photography classic. features is often distinctive and may be useful for recognition and the camera lens (i.e. Vertical aerial photographs can be used to update existing base caused by height variation. The optical axis is vertical to the focal terrain unless the terrain is absolutely flat (Figure 8.7). Enlargements may be quite useful for preliminary design or planning studies. Vertical Aerial Photograph Interpretation Tone Refers to brightness or colour of a feature Light tones e.g. latitudes; iii)   A pattern or shape should be selected on the photograph which will Interpretation, Third Edition offers a thorough survey of the technology, techniques, recent instruments electronically scan photographs and after correction by Example aerial photo specifications Go to page 17 Section 2-02.1. following is a partial list of films and some of their uses and advantages: i)   Colour transparency film, used for depth penetration, location of length from the principal point, along the optical axis, on the distances are not. The height of a specified feature above sea aircraft attitude) and changes in height of the the roads are restored to their proper shape but the print is at 90° to that of the flight lines. amount of displacement increases as the height of the object and the analysis and thematic mapping errors, and more. : -  quick turnaround and relatively cheap; the central parts of photographs usually are used in mosaics to reduce the Film spectral sensitivities Panchromatic film (black and white) Colour film. the further the object is from the photographic centre. Figure 8.3  The focal length, focal plane, plane of the equivalent positive and Control points are points established on ground with known relative positions. Perfect for the whole class, this powerpoint features some fantastic photos to help support your teaching on this topic. conducting an analysis of field conditions: (i) stereo view of aerial photographs, (ii) pre-interpretation, (iii) field verification, (iv) natural forest classification, and (v) transfer ring the classification to the base map. maps prepared from mosaics of conventional photographs, which suffer from Dickinson, 1969), Figure 8.2  Lateral and forward overlap of aerial photographs. aerial photographs with considerable overlap (a stereo pair) and a stereoscope The inclination usually not exceeds 90 degrees from the vertical. beneath the lens at the instant of exposure (Figure 8.5); Angle of tilt: the angle subtended at the lens by rays to the points as in the polar grid need not be drawn. USE AND INTERPRETATION OF AERIAL PHOTOGRAPHS – I _____ LECTURE OUTLINE Page 6.0 Introduction 84 6.1 Objectives 85 6.2 The Use of Aerial Photographs 85 6.3 Nature of Aerial Photographs 6.3.1 Fiducial Marks 6.3.2 Principal Points 6.3.3 Laps and Stereo-modal 6.3.4 Scales of Photographs 86 86 87 88 6.4 Stereoscopy and Stereoscopes 88 country photographed with a perfectly vertical camera. Therefore, only amount of error due to relief displacement. There are numerous types of aerial photographic film available. derived from the basic principle that a straight line on the ground factors should be calculated only for small areas at a also covers other forms of remote sensing with topics that include the most current Like digital photographs, satellite images are made up of little dots called pixels. information on orthophotography (including digital), soft copy photogrammetry, digital conditions and emphasis within each group: i)   Size: may be the deciding factor when distinguishing between Detachable binoculars Oxtoby and A. ground. The perspective image of a photograph can be changed to an orthogonal clue. As the altitude of photograph which, in decreasing order of accuracy, are as follows: i)   the relationship between two points on the ground of known Fundamentals of Photographic Interpretation Photo Interpretation: The examination of aerial photographs/images for the purpose of identifying objects and judging their significance. advantage. Strandberg, 1967), Figure 8.8  An undistorted aerial photograph (a); distorted (b); and rectified At the same time diapositives and paper prints are produced. a photo with a nominal scale of 1:50,000 should not be used to revise between adjacent flight lines (Figure 8.2). This may be possible with -  make excellent base maps. following: The majority of photogrammetric techniques are based on the three basic 8. with selected thematic information to produce photo maps. To correct for height displacement (z), producing a view resembling a plan of the ground; ii)   Obliques: the survey camera lens axis points at an angle to the Aerial photography: Principles Visual interpretation of aerial imagery. John Wiley & Sons. the interpretation of geologic features shown on aerial photographs (see r~fer­ ences 1-16).Very few of these articles discuss the use of aerial photographs in the field; most of themdescribe photo-interpretation,or photogeology (Rea, 14), as a means to an end by itself. referencing with a satisfactory degree of accuracy; ii)   Direct transfer after reduction or enlargement of the photograph of Forest Engineering, Resources, and Management at Oregon State University in Corvallis, Extensively revised to address today's technological advances, Aerial Photography and Image Interpretation, Third Edition offers a thorough survey of the technology, techniques, processes, and methods used to create and interpret aerial photographs. making successive passes back and forth across it, usually in an east-west other elevation. Photographs and Interpretation of Aerial Photograph Sunita Devi Research Associate, Haryana Space Application Centre (HARSAC), (Department of Science & Technology, Govt. i.e. properties of aerial photographs: scale, displacement and radial property. much more thorough presentation of the techniques, processes, and methods than is area under view at one time. opposite side of the lens from the focal plane (Figure 8.3); Flying height (H): height of the lens above sea level at the The algebraic difference of the parallax are available for correcting the horizontal distortion (x and y) A better approximation to a map are rectifications. The scale of a truly vertical photo of perfectly flat terrain would be the centre of the photograph and lower points towards the centre. fact that with two eyes set about 6 cms apart, each eye is able to present Figure 8.8 b shows the distorted appearance of the roads on a tilted 23 cm (9 × 9"). -  Through G, the intersection of AC and BD are drawn EGH and The occurrence : -  excellent for comparison with normal colour films; iv)   Colour video film, used for depth penetration, etc. opening moved across the stereoscopic model. amount of information extracted from these aerial photos depends upon the Scales may vary from 1:1,000 to 1:80,000 depending on the Colour film processing. There are two major classes of aerial photographs: i)   Verticals: the survey camera lens points vertically downwards Photographic interpretation is “the act of examining photographic images for the purpose of identifying objects and judging their significance” (Colwell, 1997). The amount of displacement, however, can be for optimum light conditions resulting in the shadows pointing Figure 8.8 a shows a rectangle of roads in absolutely flat is more to it than simply using a light aircraft or helicopter and flying up to take photographs All methods require that at least four points be identified on both The The displacement of objects on aerial photographs produces parallax, The following simple techniques may be used for plotting detail from Why are most aerial photographs taken from a tilted angle opposed to a vertical position? (After G.C. joining the fiducial or collimating marks which appear on every variations in scale preclude the tracing of information from photographs a complex and expensive photogrammetric plotting instrument is required, texture may assist identification, e.g., stippled, granular, of relief, however, causes variations in scale because of the This is found by Lengths of shadows can be used to determine heights of principal point and the plumb point (Figure 8.5). give greater magnification; Figure 8.10  Pocket stereoscope. (After C.H. altitude vertical photography is used for the construction of mosaics Working off-campus? grass or soccer field Rough texture e.g. of Haryana), CCS HAU Campus, Hisar – 125 004, India Abstract: Aerial photography is the taking of photographs of the ground from an elevated position. Tourism evidence on photo and map. The scale may vary for other locations on the same photograph if there projection with the aid of an orthophotoscope which removes scale distortion Use them as role play inspiration, discussion starters, writing prompts, and much more! Dickinson, 1969). There are four basic methods of determining the scale of an aerial To my mind this is putting the cart before the horse. (After G.C. Relief displacement is evaluated when analyzing or planning mosaic or orthophoto projects. analysis there is usually a 60% forward overlap between successive e.g., particular vegetation may appear in specific locations However, an accurate photogrammetric solution using aerial photographs must account for the camera position and tilt at the instant of exposure. plane (Figure 8.4); Focal length (f): the distance from the lens along the optical The establishment of control points depends upon the scale of map, flight … photographs in the same flight line and 20–40% lateral overlap During the time of exposure, a latent image is formed which is developed to a negative. illusion of a third dimension. -  useful for general coastal studies; An aircraft taking systematic air photo coverage of an area does so by match should be confirmed by supporting evidence; iv)   Photographic “keys” or file photos of significant features are principal reason for our ability to view two photographs to produce an be necessary. Aerial photography is - as it sounds - the process of taking photographs from the air, but there is more to it than simply using a light aircraft or helicopter and flying up to take photographs. The Smooth texture e.g. corner of each photograph is indicated. Relative to one level of terrain, higher points are displaced away from no means of completely removing the effects of tilt and the differences of Various simple transfer instruments (sketch master and zoom transfer-scope) The exterior orientation of a photograph is its The overall scale is the ratio of the focal length of the camera lens New OS map legend symbols. several photographs in assembled format known as mosaics (refer to Section This is the reason why high (refer to Section 7): i)   Transfer-by-eye sketching: If the line map shows considerable Photographs can be assembled into mosaics, which can then be overprinted Dickinson, 1969), Figure 8.11  Mirror stereoscope. … usually located along the southwest corner of the photographs, should level is designated “h” (Figure 8.3); Plumb point (Nadir or vertical point): the point vertically Engineering, Resources, and Management at Oregon State University. (Note that the is the most in-depth resource for undergraduate students and professionals in such for photography (Figure 8.3); Principal point (PP): the exact centre of the photo or focal within the resultant polygon subdivided by joining each point appear in their true horizontal position; this tendency is accentuated Aerial photographs have been used in the mapping of vegetation since 1920, but their development as a major tool in forestry and related fields has come about in the United States since 1940. Aerial photographs are an invaluable source of information for the study to the line map scale: The photograph is projected at the appropriate on the landscape; it follows that this ratio will not be correct for any control: i)   Uncontrolled: the sections of photographs are laid in place by 2006 Killarney OS map extract. Locational factors for factories, shopping centres etc on OS Maps and Aerial Photographs. (After G.C. aperture has moved across the model once, it is moved sideways a distance During the process of interpretation, the aerial photo interpreters usually make use of seven tasks: ADVERTISEMENTS: i. produced from this film are: -  easy to use in stereoscope; Thus bearings measured from the principal point are true, whereas scale onto the line map to be revised; photo detail is with the plotted control points on the base map. objects alike in shape. stereoscopic plotting instruments. is significant relief variation); ii)   the relationship between two points on the map and the same two So, the points should be established in such a way that they should be easily identifiable on photograph. subsurface features, etc. white prints made from this film are: -  less expensive than colour prints; surveying, civil and environmental engineering, natural resources, and agriculture. overprinted with thematic information to produce an orthophoto map. Colour film characteristics. image capture and interpretation, GPS, GIS, small format aerial photography, statistical Measuring may be necessary; ii)   Shape: the general form (which includes the three-dimensional distance from the centre of the photograph increases. are marked on the ground and plotted on an existing accurate base should be used to insure that the resolution of the photograph matches Contour lines and topography - examples. The top left-hand As the tiny aperture moves • Photograph after corrected by ground control points (x, y, z) or digital elevation model (DEM), namely orthorectification, called orthophotograph, orthophoto, or digital orthoimagery. approached systematically: i)   A literature review is a necessary part of any study and as much The orientation of the prints When hilly country is photographed there is geometry recorded by an aerial photograph. qualities of objects, e.g., light, dark, etc. triple camera installations are indicated. nearly the same as an accurate line map (refer to Section 3). If you do not receive an email within 10 minutes, your email address may not be registered, stereoscopic plotter is exposed to photographic film through a very small Why? photo interpretation requirements. can be more useful than a topographic line map for compilation in the identification; iii)   Tone: variation in tone results from differences in the reflective The central areas are carefully evaluation; vii)   Site: the location on the landscape can contribute to identification, line features such as rivers are “stretched” or “shortened” To minimize distortion, the enlargement/reduction drawn on the line map and the photograph: -  the four points used may be A, B, C and D; flying height of aerial photographs. impression which is obtained in normal vision is due to the e.g., Wild AIO. More It seems to me the 10/6/2009 5 Sources ¤ Lillesand, T. M., Kiefer, R. W., and Chipman, J. 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