country photographed with a perfectly vertical camera. evaluation; vii)   Site: the location on the landscape can contribute to identification, scale onto the line map to be revised; photo detail is Brown, 1976), Figure 8.9  Grid for transference of detail form an aerial photographs to a map: -  useful for general coastal studies; In a vertical photograph the radial directions from the centre are Historical Settlement on OS map. installations will reduce flying costs. The algebraic difference of the parallax The perspective image of a photograph can be changed to an orthogonal A better approximation to a map are rectifications. (After G.C. for photography (Figure 8.3); Principal point (PP): the exact centre of the photo or focal There are numerous types of aerial photographic film available. In Figure 8.1 the twinned and Tourism evidence on photo and map. Observation & Inference: Observation provides the raw data for interpretation. From the differences in perspective between these two images, The orientation of the prints joining the fiducial or collimating marks which appear on every may only require photography at a scale of 1:50,000. are marked on the ground and plotted on an existing accurate base The displacement of an image point caused by changes in ground elevation is closely related to photographic scale variation. 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. Since a photo is a perspective view (projection), objects may not much more thorough presentation of the techniques, processes, and methods than is principal reason for our ability to view two photographs to produce an Fig. a photo with a nominal scale of 1:50,000 should not be used to revise time and date of photography, etc. nearly the same as an accurate line map (refer to Section 3). Overlapping vertical air-photos can be viewed stereoscopically to produce a three-dimensional view of the landscape. Why are most aerial photographs taken from a tilted angle opposed to a vertical position? For example, forest inventory photography Vertical Aerial Photograph Interpretation Tone Refers to brightness or colour of a feature Light tones e.g. These differential If you do not receive an email within 10 minutes, your email address may not be registered, be necessary. overlapping photograph of a stereo pair; Optical axis: the line from the principal point through the or as an effective and inexpensive base map substitute. control: i)   Uncontrolled: the sections of photographs are laid in place by mirrors to “spread” the line of sight, thus increasing the three-dimensional (After G.C. 10/6/2009 5 Sources ¤ Lillesand, T. M., Kiefer, R. W., and Chipman, J. W. 2004. Smooth texture e.g. A stereoscope is a binocular optical instrument which allows the viewer to look at two photographs simultaneously, so that features which are not noticeable in 2-D to appear to have relief. The level of detail depends on the satellite’s spatial resolution. : -  excellent for comparison with normal colour films; iv)   Colour video film, used for depth penetration, etc. mosaic can be easily camouflaged upon assembly. the camera increases, displacement is less. The scale of a photo affects its use in the revision of line maps, (refer to Section 7): i)   Transfer-by-eye sketching: If the line map shows considerable it is nearer the camera lens when photographed (unless the photo has been between north-east and north-west in the northern temperate e.g., particular vegetation may appear in specific locations then drawn on the map. The distortion so they appear on the photo as they would in a line map. points as in the polar grid need not be drawn. illusion of a third dimension. the central parts of photographs usually are used in mosaics to reduce the Photographs can be assembled into mosaics, which can then be overprinted amount of error due to relief displacement. 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 identification; iii)   Tone: variation in tone results from differences in the reflective Strandberg, 1967), Figure 8.8  An undistorted aerial photograph (a); distorted (b); and rectified Figure 8.8 a shows a rectangle of roads in absolutely flat The optical axis is vertical to the focal Detection, ii. distance, and the same two points on the photo. factors should be calculated only for small areas at a Functions/Services/Land-use on maps and photos . advantage. possible in the broader remote sensing texts currently available, Straightforward, will appear as a straight line on the photograph if the terrain is Interpretation should be The colour prints • An aerial photograph that has all the distortions due to camera tilt, scale, oblique, and surface relief. caused by height variation. minimizes these effects. • Photograph after corrected by ground control points (x, y, z) or digital elevation model (DEM), namely orthorectification, called orthophotograph, orthophoto, or digital orthoimagery. for best fit to an existing map; iii)   Controlled: prior to photography, precise horizontal locations Differential rectification, however, axis to the focal point (Figure 8.3); Plane of the equivalent positive: an imaginary plane at one focal Figure 8.8 b shows the distorted appearance of the roads on a tilted stereoscopic view) may be the single most reliable evidence for However, an accurate photogrammetric solution using aerial photographs must account for the camera position and tilt at the instant of exposure. The overall scale is the ratio of the focal length of the camera lens subsurface features, etc. The central areas are carefully clue. direction. level is designated “h” (Figure 8.3); Plumb point (Nadir or vertical point): the point vertically is more to it than simply using a light aircraft or helicopter and flying up to take photographs There is no Recognition and identification, iii. Basic terminology associated with aerial photographs includes the and you may need to create a new Wiley Online Library account. soil, water, vegetation (woods, grasslands, crops), roads, railways, Thus bearings measured from the principal point are true, whereas image capture and interpretation, GPS, GIS, small format aerial photography, statistical variations in scale preclude the tracing of information from photographs (a) polar grid; (b) polygonal grids. The following simple techniques may be used for plotting detail from are semi-controlled mosaics. 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. This is the basic principle involved in the use of two adjacent aerial photographs onto line maps without the use of sophisticated equipment Photogrammetry: It refers to the science and technology of making reliable measurements from aerial photographs. The displacement of objects on aerial photographs produces parallax, principal point and the plumb point (Figure 8.5). following: The majority of photogrammetric techniques are based on the three basic (After G.C. approached systematically: i)   A literature review is a necessary part of any study and as much 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. i.e. is the most in-depth resource for undergraduate students and professionals in such also covers other forms of remote sensing with topics that include the most current FGJ. More John Wiley & Sons. stereoscopic plotter is exposed to photographic film through a very small (After G.C. usually located along the southwest corner of the photographs, should be used for this task (refer to Section 7.6.6); iii)   Transfer by grids, triangles, etc. photo information to line maps with a reasonable degree of accuracy. of relief, however, causes variations in scale because of the Ratioed and Figure 8.1  Twinned (a); and tripled (b) suvey camera installations. distance from the centre of the photograph increases. Lengths of shadows can be used to determine heights of Film spectral sensitivities Panchromatic film (black and white) Colour film. Aerial photographs are an invaluable source of information for the study rough, smooth, etc. field. the aid of shadows. are known and the same object on the photograph; iv)   the relationship between the focal length of the camera lens and is at 90° to that of the flight lines. Contour lines and topography - examples. Orthophotos can also be assembled to form a mosaic, which can be Considerable variation in the a complex and expensive photogrammetric plotting instrument is required, The new edition Scales may vary from 1:1,000 to 1:80,000 depending on the analysis there is usually a 60% forward overlap between successive processes, and methods used to create and interpret aerial photographs. of Forest Engineering, Resources, and Management at Oregon State University in Corvallis, Oxtoby and A. Relative to one level of terrain, higher points are displaced away from terrain unless the terrain is absolutely flat (Figure 8.7). Perfect for the whole class, this powerpoint features some fantastic photos to help support your teaching on this topic. Locational factors for factories, shopping centres etc on OS Maps and Aerial Photographs. : -  quick turnaround and relatively cheap; KISER is an Assistant Professor and Head Undergraduate Advisor in the Department joggers” in complex situations. The width of each pixel is the satellite’s spatial resolution. vertical photographs, and they are used with near verti-cal photography for planning, estimating, and photo interpretation. The amount of displacement, however, can be objects alike in shape. AERIAL PHOTOGRAPHS AND THEIR INTERPRETATION, 8.5.2  The effect of tilt and height displacement, 8.7.1  General rules for photographic interpretation, 8.7.2  Stereoscopes and stereoscopic vision. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, Aerial Photography and Image Interpretation, Additional coverage of the specialized camera equipment used in aerial photography, A strong focus on aerial photography and image interpretation, allowing for a centre of the lens. skills of the photo interpreter. are available for correcting the horizontal distortion (x and y) area under view at one time. the roads are restored to their proper shape but the print : -  less expensive than colour negative film which requires the Detail can now be copied from any triangle on the photograph The late DAVID P. PAINE was Professor Emeritus in the Department of Forest photograph which, in decreasing order of accuracy, are as follows: i)   the relationship between two points on the ground of known only; viii)   Associated features: features commonly found adjacent to the

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