【正文】 ccount. In plane surveying relatively small areas are under consideration, and it is taken that the earth39。s surface is flat, . it gives a horizontal plane. Measurements plotted will represent the projection on the horizontal plane of the actual field measurements. For example, if the distance between two points A and B on a hillside is l, the distance to be plotted will be lcosa, where a is the angle line AB makes with the horizontal, assuming a uniform slope.A horizontal plane is one which is normal to the direction of gravity, as defined by a plumb bob at a point, but owing to the curvature of the earth such a plane will in fact be tangential to the earth39。s surface at the point. Thus, if a large enough area is considered on this basis, a discrepancy will bee apparent between the area of the horizontal plane and the actual curved area of the earth39。s surface.It can be shown that for surveys up to 250km2 in area this discrepancy is not serious, and it is obvious therefore that plane surveying will be adequate for all but the very largest surveys. However, precautions are required when connecting such surveys to control points established and coordinated by geodetic surveys.Geodetic surveying太原理工大學(xué)畢業(yè)設(shè)計(jì)說明書41Geodetic surveying is actually a branch of surveying distinguished both by use and technique. As will be explained shortly, frameworks of angular and distance measurements between points are necessary to control all surveys and when surveying large areas, such as a whole country, these measurements must be taken to the highest possible standard. Thus, highaccuracy techniques of measurement are associated with geodetic surveying and as already mentioned, over these large areas the curvature of the earth must be considered. The study of the size and shape of the earth and its gravity field is known as geodesy, hence the name of this type of surveying. Topographic surveyingThese produce maps and plans of the natural and manmade surveys features. There is no clear distinction between a map and a plan but it is generally accepted, however, that in a plan detail is drawn such that it is true to scale, whilst in a map many features have to be represented by symbols, the scale being too small. Height information can be added either as spot heights, which are individual height points, or contours, which give a less detailed, but more visual, representation of the area. Frequently spot heights only are shown on plans.Plans tend to be used for engineering design and administration purposes only, but maps have a multitude of uses, navigational, recreational, geographical, geological, military, exploration, their scales ranging from 1:25 000 to, say, 1:1000000. Engineering Surveying These embrace all the survey work required before, during and after any engineering works. Before any works are started largescale topographical maps or plans are required as a basis for design. The proposed position of any new item of construction must then be marked out on the ground, both in plan and height, an operation generally termed setting out, and finally, 39。as built39。 surveys are often required.Especially for the design and construction of new routes, . roads, and railways, but in many other aspects of surveying, it is often required to calculate the areas and volumes of land and data for setting out curves for route alignment.Typical scales are as follows:太原理工大學(xué)畢業(yè)設(shè)計(jì)說明書42Architectural work, building work, location drawings: 1/50, 1/100, 1/200.Site plans, civil engineering works: 1/500, 1/1000, 1/1250, 1/2022, 1/2500.Town surveys, highway surveys: 1/1250, 1/2022, 1/2500, 1/5000, 1/10000, 1/20220, 1/50000. Cadastral surveyingThese are undertaken to produce plans of property boundaries for legal purposes. In many countries the registration of ownership of land is based on such plans. Mine SurveyingMine surveying is a discipline concerned with surface and underground measurements, obtaining data in digital form and making graphical representation for prospecting mineral deposits, for exploitation of mines and their construction.Mine surveying came into being a few centuries ago when extensively developing mining called for the determination of the boundaries of the mining claims. The early period of mine surveying may be considered as the art of running underground traverses. However, as it developed, mine surveying became a plex discipline that included, apart from techniques of mine surveying, the estimation of the accuracy of measurements and calculations based on the method of least squares and probability theory, the mine surveying instrumentation, the geometry of mineral resources, study of tectonics, shifts and pressures of rocks (geomechanics) etc. All these aspects of mine surveying have the same objectives, i. e. the precision of geological exploration as well as the safety and efficiency in working a mine. The impetus received, by geological exploration and mining in the last few years results in a larger spectrum and plexity of the tasks to be faced by mine surveyors, called also mineral surveying by introducing sophisticated equipment. There is a trend to create specialpurpose groups to conduct one type of mine surveying operations. Certain progress has been made in the methods of mine surveying, special manuals and regulations have been prepared, new solutions of the problems of orientation and construction of reference s have been suggested. Moreover, we are witnessing the advent of highprecision theodolites and optical range finders for densification of 太原理工大學(xué)畢業(yè)設(shè)計(jì)說明書43reference s and the introduction of new instruments and novel methods for surveys of open pits. Lasers have recently bee very popular to give lines and grades and check on the directions of mines and provide control for such operations as mine shaft equipment, laying railway tracks, installing conveyors, pu