摄影测量学毕设论文外文翻译翻译+原文.docx

1、摄影测量学毕设论文外文翻译翻译+原文PhotogrammetryThe principles of photogrametry can be traced back to the works of Leonardo da Vinci in the late fifteenth century. Through his work in the fields of geometry, optics, mechanics, and geophysiscs, da Vinci graphically illustrated the concepts of aerodynamics and optica

2、l projection. It is not until the mid 1800s that the field of photogrammetry came into its own, particularly within the European community. The term photogrammetry was first coined in 1855 by the European geographer Kersten, and was in common use throughout Europe by 1900.The term, however, did not

3、win wide acceptance in the United States until 1934.In that year, the American Society of Photogrammetry (ASP) was founded. Types of Photogrammetry The ASP currently consider photogrammetry to be the art, science, and technology of surveying and measuring by photographic and other energy-emitting pr

4、ocesses. The procedure is extensively used in topographic mapping, and can be applied from the ground as well as in the air. Aerial photogrammetry, though, is the procedure most commonly used in mapping. It has all but eliminated the need for extensive field surveys. Ground, or terrestrial, photogra

5、mmetry is used only as a supplement and complement to the aerial process, or in areas with unusual physical characteristics. Like other professional disciplines, photogrammetry consists of a variety of specialty areas. For example, there are the two broad areas if terrestrial (ground) and aerial (ai

6、r) photogrammetry. Other specialty areas of photogrammetry are defined as to the technology or energyemitting process used. Some of the types of photogrammetry used in the mapping and topographic field are discussed here.Radargrammetry is the use of radar as a measuring device to describe the physic

7、al characteristic of an area of the earths surface. X-ray photogrammetry employ X-ray to collect surveying data, and the use of motion pictures for surveying is called cinephotogrammetry.Hologrammetry is the use of holographs images projected by the use of coherent light systems such as lasers to me

8、asure surface characteristics. In monoscopic photogrammetry, single images or photographs are use or surveying purposes. Finally there is space or satellite photogrammetry, in which spacecraft or satellites are utilized as utilized as a platform for taking surface measurements. This type is also ref

9、erred to as extraterrestrial photogrammetry.Aerial Photography: The aerial photograph is perhaps the most familiar product of the photogrammetry field. It application in the mapping and topographic dada collection process combines the use of scientific and artistic procedures and techniques. Aerial

10、photogrammetry, then, is the use of photographic images taken from an airborne base for surveying purpose.The success and accuracy of an aerial photography mission is dependent upon a number of important factors , including the following:1. The use of correct photographic equipment, lenses, and supp

11、lies;2. Appropriate correct photographic materials, such as film, print and duplication materials, reflection print materials, and plates; 3. The photographic team (pilot, photographer, and film processor ) ;4. Weather conditions;5. The position of the sun when the photographs are taken.Classificati

12、ons of Aerial Photography Aerial photography is a complex and dynamic profession, as is the photogram metric field in general. Aerial photography requires a vast array of equipment, technologies, and procedures. Therefore, to classify the various types of aerial photographs used in the mapping and t

13、opographic field, The ASP has identified four criteria: the orientation of the camera axis, the tens systems, the spectral range, and the mode of scanning these criteria are discussed in this section. Orientation of Camera Axis This refers to the angle at which the camera is in tentionally positione

14、d at the time of the photograph. Ad shown in fig.23-1, these are two orientations of axis, used in aerial photography. These are the vertical orientation axis and the oblique orientation axis.With a vertical orientation axis, the photograph is taken when the camera is intentionally positioned as nea

15、rly vertical-or as close to 90 to the earths surface-as possible. Because of the earths curvature and aeronautical factors, it is impossible to obtain a true theoretical vertical picture (hence the qualifier “as nearly vertical as possible”). For practical mapping purposes, however, the “near vertic

16、al” is more than sufficient.The vertical orientation axis is the most common type of aerial photograph used in mapping. This type of photograph cam be easily converted into map drawings: it fives a sense of an ex fisting map or chart. The three major advantages of using the vertical orientation axis

17、 are that measurements can be easily taken off the photograph and transferred, surface objects and landmarks can be easily identifies, and the amount of hidden ground (areas not observable in the photograph) will be minimal.Oblique orientation axis photographs are images intentionally registered off

18、 vertical, and in the oblique, technically, this means that the camera lens angle is aimed between true horizontal and vertical. These photographs can be further subclassified into high oblique and low oblique. high oblique photographs pertain to the optical axis of the camera being at a high angle

19、to the vertical, while low-oblique photographs have the optical axis of the camera at a low angle to the vertical.Oblique photographs have a limited application for mapping. They are only of practical use in situations requiring small-scale drawings. The two advantages of the oblique photographs are

20、 that they provide a stereoscopic or three-dimensional perception of the photographed area, and they can provide a larger area coverage than is provided by vertical photographs .there are, however, three significant disadvantages to using these photographs for map and topographic drawings. Fist, the

21、re is a loss of imagery and resolution. Second, the scale constantly reduces as one observes images a way from the camera. Third disadvantage is that highly skilled personnel and specialized equipment are needed to generate an accurate and useful product, resulting in higher cost.Lens Systems These

22、are classified by the number and configuration of the camera lenses used for aerial photographs. Within this framework, all lens systems, and the multiple lens systems.The single-lens system is the most popular and frequently used system in aerial photography. It is applicable for either vertical or

23、 oblique photographs. The single-lens system usually employs a 153 millimeter (mm) focal length with a 228228 mm format , while using only one lens per shot. By comparison, super wide-angle lens cameras are seldom used. If used, however, it is for photographic missions over low-relief terrain.Multip

24、le-lens systems consist of two or more lenses. These systems can be sub classified by the type of mounting used. The fist mounting is where the lenses are separately mounting in different cameras and the shutters are synchronized for simultaneous exposures. In each case, the lenses are fixed at diff

25、erent optical axes so that the photographs can be used on a stereoscope. The accuracy, and usefulness of photographs taken with a multiple-lens system are dependent upon the care and accuracy, of the calibration and retention of the axis angles.Another term used for the multiple-lens system is multi

26、spectral systems consist of two or more cameras, simultaneous exposures of an area of land, and the choice of different films and/ or filter combinations.Spectral Range This criterion refers to the entire range of light on the spectrum. The vast majority, of aerial photograph is limited to the range

27、 of the spectrum that can be observed by the human eye. This is called the optical range .in some situations, aerial photographs are used to record images within the infrared range.Spectral is measured in terms of micrometers (um). As shown in Fig.23-2, the optical range is from 0.4 um to 0.8um um,

28、while the infrared range starts at 0.8 um. With the use of photographic film capable of recording optical range image, it is also possible to record some infrared images at the lower end of the scale (i.e., 0.8 um and 0.9 um). Photography further into the infrared range requires the use of special f

29、ilm and procedures. Because infrared is used to photograph temperature difference, it is also referred to as thermal photography. Mode of Scanning This is the last criterion used in classifying aerial photographs. There are three scanning modes used in aerial photography: the single frame, panoramic

30、 and continuous strip. In this sense, scanning refers to how the camera lens functions during the photographic process.Of the three scanning modes, the single-frame camera, the entire frame (format) is exposed through a lens that is fixed in relation to the focal plane. These cameras are the easiest

31、 to use and the least expensive. They also provide the most accurate data to transfer onto maps and topographic drawings. There are, however, two disadvantages to single frame photographs. First, these is a resolution as one moves away from the center of the photography.The problems associated with

32、single frame photographs can be solved with the use of panoramic or continuous-strip cameras. Panoramic photography combines a high resolution at the center of the picture over the total angle scanned, which in some cases can be from horizon to horizon. Panoramic photography is accomplished by using

33、 narrow angles ,fast lens systems, by scanning the lens system though large angles across the flight path, and by using normal-width film and advancing it parallel to the scanning direction at ground speed.Continuous-strip photography eliminates the need for a conventional shutter system. The images are exposed on the film as the film