gre考试阅读真题解析(B)

　　The term remote sensing refers to the techniques of measurement and interpretation of phenomena from a distance. Prior to the mid-1960s the interpretation of film images was the primary means for remote sensing of the Earths geologic features. With the development of the optomechanical scanner, scientists began to construct digital multispectral images using data beyond the sensitivity range of visible light photography. These images are constructed by mechanically aligning pictorial representations of such phenomena as the reflection of light waves outside the visible spectrum, the refraction of radio waves, and the daily changes in temperature in areas on the Earths surface. Digital multispectral imaging has now become the basic tool in geologic remote sensing from satellites.

　　The advantage of digital over photographic imaging is evident: the resulting numerical data are precisely known, and digital data are not subject to the vagaries of difficult-to-control chemical processing. With digital processing, it is possible to combine a large number of spectral images. The acquisition of the first multispectral digital data set from the multispectral scanner aboard the satellite Landsat 地球资源卫星) in 1972 consequently attracted the attention of the entire geologic community. Landsat MSS data are now being applied to a variety of geologic problems that are difficult to solve by conventional methods alone. These include specific problems in mineral and energy resource exploration and the charting of glaciers and shallow seas.

　　A more fundamental application of remote sensing is to augment conventional methods for geologic mapping of large areas. Regional maps present compositional, structural, and chronological information for reconstructing geologic evolution. Such reconstructions have important practical applications because the conditions under which rock units and other structural features are formed influence the occurrence of ore and petroleum deposits and affect the thickness and integrity of the geologic media in which the deposits are found.

　　Geologic maps incorporate a large, varied body of specific field and laboratory measurements, but the maps must be interpretative because field measurements are always limited by rock exposure, accessibility and labor resources. With remote-sensing techniques it is possible to obtain much geologic information more efficiently than it can be obtained on the ground. These techniques also facilitate overall interpretation. Since detailed geologic mapping is generally conducted in small areas, the continuity of regional features that have intermittent and variable expressions is often not recognized, but in the comprehensive views of Landsat images these continuities are apparent. However, some critical information cannot be obtained through remote sensing, and several characteristics of the Landsat MSS impose limitations on the acquisition of diagnostic data. Some of these limitations can be overcome by designing satellite systems specifically for geologic purposes; but, to be most effective, remote-sensing data must still be combined with data from field surveys and laboratory tests, the techniques of the earlier twentieth century.

　　17. By using the word interpretative in line 40, the author is indicating which of the following?

　　 Some maps are based more on data from aerial photography than on data from field operations.

　　 Some maps are based almost exclusively on laboratory measurements.

　　 Some maps are based on incomplete data from field observations.

　　 Some maps show only large geologic features.

　　 Some maps can be three-dimensional.

　　18. With which of the following statements about geologic mapping would the author be most likely to agree?

　　 Geologic mapping is basically an art and not a science.

　　 Geologic mapping has not changed significantly since the early 1960s.

　　 Geologic mapping will have limited practical applications until remote-sensing systems are perfected.

　　 A developmental milestone in geologic mapping was reached in 1972.

　　 Without the present variety of remote-sensing techniques, geologic mapping could not be done.

　　19. According to the passage, measurements of which of the following can be provided by the optomechanical scanner but not by visible-light photography?

　　 The amount of visible light reflected from oceans

　　 The density of foliage in remote areas on the Earths surface

　　 Daily temperature changes of areas on the Earths surface

　　 The degree of radioactivity emitted by exposed rocks on the Earths surface

　　 Atmospheric conditions over large landmasses

　　20. It can be inferred from the passage that a major disadvantage of photographic imaging in geologic mapping is that such photography

　　 cannot be used at night

　　 cannot focus on the details of a geologic area

　　 must be chemically processed

　　 is always enhanced by digital reconstruction

　　 cannot reflect changes over extended periods of time

　　21. It can be inferred from the passage that Landsat images differ from conventional geologic maps in that Landsat images

　　 reveal the exact size of petroleum deposits and ore deposits

　　 indicate the continuity of features that might not otherwise be interpreted as continuous

　　 predict the movements of glaciers

　　 provide highly accurate data about the occurrence of mineral deposits

　　 reveal the integrity of the media in which petroleum deposits and ore deposits are found

　　22. The passage provides information about each of the following topics EXCEPT:

　　 the principal method of geologic remote sensing prior to the mid-1960s

　　 some of the phenomena measured by digital multi-spectral images in remote sensing

　　 some of the practical uses of regional geologic maps

　　 the kinds of problems that are difficult to solve solely through conventional methods of geologic mapping

　　 the specific limitations of the Landsat multi-spectral scanner

　　23. The passage suggests which of the following about the conventional methods mentioned in line 29?

　　 They consist primarily of field surveys and laboratory measurements.

　　 They are not useful in providing information necessary for reconstructing geologic evolution.

　　 They have rarely been used by geologists since 1972.

　　 They are used primarily to gather compositional information about geologic features.

　　 They are limited primarily because of difficulties involved in interpreting film images.

　　Although the development of new infrastructure is usually determined by governmental planning, sometimes this development can be planned more flexibly and realistically by private investors who anticipate profit from the collection of user fees. Such profits can contribute to the financing of more infrastructure if demand proves great enough, whereas the reluctance of developers to invest in such projects can signal that additional infrastructure is not needed. During the economic boom of the 1980s, for example, the state of Virginia authorized private developers to build a $300 million toll road . These developers obtained the needed right-of-way from property owners, but by 1993 they still had not raised the necessary financing. The unwillingness of investors to finance this project does not negate the viability of privately financed roads; rather, it illustrates a virtue of private financing. If a road appears unlikely to attract enough future traffic to pay for the road, then it should not be built.

　　24. The primary purpose of the passage is to

　　 build a case for increasing the development of new infrastructure

　　 advocate an alternative to government financing of infrastructure

　　 explain the failure of a privately financed venture

　　 suggest the types of infrastructure most appropriate for private financing

　　 argue against government restrictions on developing new infrastructure

　　25. The passage implies that the governmental planning mentioned in line 3 may lead to which of the following problems?

　　 Improper use of profits derived from user fees

　　 Unduly slow development of necessary new infrastructure

　　 Unrealistic decisions about developing new infrastructure

　　 Incorrect predictions about profits to be gained from user fees

　　 Obstruction of private financing for the development of new infrastructure

　　26. According to the passage, which of the following is true of the toll road mentioned in line 12?

　　 After it was built, it attracted too little traffic to pay for its construction.

　　 It was partially financed by the state of Virginia.

　　 Its development was authorized during an economic boom.

　　 Its construction was controversial among local residents.

　　 Its developers were discouraged by governmental restrictions on acquiring the necessary land.

　　27. The passage suggests that which of the following would occur if a privately financed bridge that proved to be profitable failed after a number of years to meet the demands of traffic?

　　 Private developers who financed the bridge would rely on governmental authorities to develop new infrastructure.

　　 User fees would be increased so that usage would become more costly.

　　 Governmental authorities would be reluctant to rely on private contractors to develop a new bridge.

　　 The success of the project would be jeopardized by public dissatisfaction with the projects adequacy.

　　 Profits generated by user fees would be used to help finance the construction of new infrastructure to alleviate the traffic problem.

答案：17-27：CDCCBEABCCE