2013年硕士研究生复试(全斌)-E

2013年硕士研究生复试<专业英语>试题Translate the following into Chinese:The Reliability of a Survey and Errors Since every technique of measurement is subject to unavoidable error, surveyors must be aware of all sources and types of error and how they combine. If the accuracy of a measurement is defined as the nearness of that value to its true value (a quantity we can never know) then a surveyor must ensure that the techniques he chooses will produce a result that is sufficiently accurate. He must know, therefore, how accurate he needs to be, how to achieve this accuracy and how to check that the required accuracy has been achieved.The Global Positioning SystemThe Global Positioning System(GPS) is revolutionizing surveying technology . GPS shifts the scene of surveying operations from ground-to –ground measurements to ground –to- sky, with obvious implications: visibility of marks is no longer a criterion for their location: operations are possible in nearly all kinds of weather and can be performed during day or night; and the skills required to utilize the technology are different both in field operations and data processing. The simultaneous visibility of multiple satellites allows effective cancellation of the major sources of error in satellite observations, with the result that with GPS, relative positioning accuracies of one part per million (ppm) or better over distances from one kilometer to thousands of kilometers are possible. This means that GPS can compete with terrestrial techniques over short distances.GPS was designed primarily as a navigation system, to satisfy both military and civilian needs for real-time positioning. This positioning is accomplished through the use of coded information, essentially clever timing signals, transmitted by the satellites. Each GPS satellite transmits a unique signal on two L-band frequencies: L1 at 1575.42MHz and L2 at 1227.60MHz (equivalent to wavelengths of approximately 19 and 24 cm, respectively). The satellite signals consist of the L-band carrier waves modulated wi th a “Standard “or S code (formerly called the C/A code ), a “precise “ or P code and a Navigation Message containing,amongst other things, the coordinates of the satellites as functions of time-the “Broadcast Ephemerides ’’. The S code which is intended mainly for civilian use , yields a range measurement precision of about 10 m , The navigation service provided by this code is referred to as the Standard Positioning Service (SPS), The P code is therefore referred to as the Precise Positioning Service (PPS), Although both codes can be used for surveying , a more accurate method is to measure the phase of the carrier signal.What is Photogrammetry?Photogrammetry is the technique of measuring objects (2D or 3D) from photo-grammes. We say commonly photographs, but it may be also imagery stored electronically on tape or disk taken by video or CCD cameras or radiation sensors such as scanners.The results can be:coordinates of the required object-pointstopographical and thematic mapsand rectified photographs (orthophoto).Its most important feature is the fact, that the objects are measured without being touched. Therefore, the term remote sensing is used by some authors instead of photogrammetry. Remote sensing is a rather young term, which was originally confined to working with aerial photographs and satellite images. Today, it includes also photogrammetry, although it is still associated rather with image interpretation.Image Processing and AnalysisMany image processing and analysis techniques have been developed to aid the interpretation of remote sensing images and to extract as much information as possible from the images. The choice of specific techniques or algorithms to use depends on the goals of each individual project. In this section, we will examine some procedures commonly used in analyzing/interpreting remote sensing images.Pre-ProcessingPrior to data analysis, initial processing on the raw data is usually carried out to correct for any distortion due to the characteristics of the imaging system and imaging conditions. Depending on the user's requirement, some standard correction procedures may be carried out by the ground station operators before the data is delivered to the end-user. These procedures include radiometric correction to correct for uneven sensor response over the whole image and geometric correction to correct for geometric distortion due to Earth's rotation and other imaging conditions (such as oblique viewing). The image may also be transformed to conform to a specific map projection system. Furthermore, if accurate geographical location of an area on the image needs to be known, ground control points (GCP's) are used to register the image to a precise map (geo-referencing).Perspectives on GIS Development in ChinaResearches and applications of Geographic Information Systems (GIS) in China started in the early 1980s. In the early period, the development of GIS was mainly depended on the progress and applications of remote sensing, aerial photography, as well as computer aided design (CAD). In recent years, with the development of GPS and Internet technology, GIS has being developed vigorously in the country. Looking ahead to the 21st century, a new era of "Digital Earth" and "Cyberspace" is coming, which will provide a great opportunity as well as a challenge to the China's GIS circles.。