测绘专业英语1UNIT-19word版本

1、测绘专业英语1UNIT-19consist of only several items, in the simplest routine investigation, or of hundreds or thousands of different data, in very complex or critical conditions. The rate of monitoring movements may be annually, monthly, weekly, daily, hourly, or even more frequently.Detecting and quantifyi

2、ng movements require the use of very precise equipment. Such movements are very small and to accurately measure them requires meticulous fieldwork as well as rigorous analysis of observed data. Deformation monitoring techniques can be generally divided into geotechnical , structural and geodetic (su

3、rvey) methods. The geodetic methods (highly understood by engineering surveyors) that can be used are Global Positioning System (GPS) , close-range photogrammetry with the use of terrestrial camera, precise theodolite and levels, total station,laser scanners, and vibration monitoring systems, a very

4、 long baseline interferometry and satellite laser ranging. A number of traditional surveying techniques have also been modifiedand applied to yield the highest possible accuracies. Geodetic measurements involve the observables of horizontal angles, or direction; spatial distance; and height differen

5、ce. Geotechniacl measurements consist of similar geometric quantities, but over a much smaller extent than for geodetic measurements (distances to a few meters rather than hundreds of meters), as well as measurements of the physical or mechanical state of the object being monitored.The survey method

6、s can be further subdivided into the survey network method and direct measurement method. In geodetic method there are two types geodetic networks, namely the reference (absolute) and relative network.Monitoring SchemesA deformation survey requires the assessment of project expectations. This would

7、include accuracy statements in order to detect the movement and external effects of theobject suspected of movement. The observation period and frequency must also be established. The selection of most appropriate technique or combination of techniques for any particular application will depend upon

8、 cost, the accuracy required, and the scale of the survey involved. Therefore several aspects related to the optimal design of the networks, measurement and analysis techniques suited to the monitoring surveys have to be considered. The design of monitoring scheme should satisfy not only the best ge

9、ometrical strength of the network but should primarily fulfill the needs of subsequent physical interpretation of the monitoring results. Selection of monitoring techniques depends heavily on the type, the magnitude and the rate of the deformation. Therefore, the proposed measuring scheme should be

10、based on the best possible combination of all available measuring instrumentation. A common feature for both geodetic and satellite methods in monitoring scheme involves the following three stages: The design of the scheme required to undertake the deformation survey must consider the instrumentatio

11、n to be used, the geometry of the network, the location of observables points, the types of observables, preanalysis of possibly environmental influences, and frequency of observation of the observables to the expected form of deformation. The reference datum must be appropriate, secure, and stable

12、and not influenced by the suspected or anticipated movement within the local site area.The execution process that runs a designed network into reality should be carefully done, which deals with both the documentation of the proposed network stations and the actual field measurement techniques in whi

13、ch the equipment used must be adjusted and in good working order with appropriate calibrations completed.Data processing deals with the processing and analysis of the collected geodetic data, quality assurance andcontrol that must be followed to confirm the expected results.Processing occurs simulta

14、neously with capture and subsequent to capture with different tasks at each time. During capture, the points involved must be identified ,an ancillary observations, such as temperature, must be requested along with dealing with the observation. The observation would likely be repeated in order to ob

15、tain a mean and an estimate of its standard deviation and the mean would be compared with the predicted or most recent value as a check on consistency. Subsequent processing would further reduce the observation and the data into series file or campaign file following the structure of the data manage

16、ment system. Consistency would be checked either again for the observation or further for the reduced data.Trend AnalysisOnce more than one campaign has been observed or once enough data are contained in a series, it is necessary to determine the tendency that is being exhibited in space or over tim

17、e or both. The observed tendencies are then brought together to suggest possible forms of models, i.e., the choice of parameters to be estimated. The trend analysis acts as a filter by extracting the behavior of interest, e.g., the annual trend or rate, from the time series, e.g., the noise being th

18、e seasonal cycle that is a reaction to the change in temperature. The extracted trends become the input or “observations” in the modeling and , therefore, it is necessary to have measures of variance associated with each trend. The spatial trend can be derived for one or two dimensional networks by considering the differences in coor