An approach for improving the precision on short-range electronic distance measurement trigonometry
Consider the trigonometric leveling method is simple, flexible and less limited by terrain conditions, it commonly used to inconveniently implemented area. Through the total station rapid development, the horizontal distance measuring between station and target for the traditional triangulation has been substituted by a slope from the Electronic Distance Measurement(EDM) measured. When combined with the appropriate methods of observation and error correction, short-range EDM trigonometric levelingshould be able to improve the accuracy levels of precision leveling. It can be enhanced the efficiency of leveling jobs. The main error of short-range EDM trigonometric leveling is from atmospheric refraction, earth curvature and measurement error of height of instrument and prismatic. The first two errors can be reduced by reciprocal observation and intermediate point. Moreover, intermediate point just only measure the prismatic height between start and end point of the measuring leveling line, The results accuracy and observation efficiency is increased. In this study, about 2km selected sections of Highway 84 at Tainan Yujing District is chosen be an experimental zone. Three kinds of closed leveling line, 200m, 400m and 600m is consisted in this measured planning. Then, non-reciprocal observation, reciprocal observation and intermediate point are introduced to implement the measurement. Experimental results show that the EDM triangle elevation for 600m range or less, the fourth-level observation precision can be achieved in non-reciprocal observation. However, the loop closure error will be caused no any grade leveling accuracy. For the reciprocal observation or intermediate method, third-level precision of measurement accuracy and loop closure error can be accomplished. The results show that the short-range EDM triangle elevation has a higher level of feasibility to instead of the traditional measure.
Functional Models and New Stochastic Model in Combined Leveling Nets
The aim of this study is to improve functional models and to form a new stochastic model that takes into account both different measurement methods and important sources of errors affecting the accuracy of the measurements in a combined leveling net measured by different instruments and measurements methods. In this study, three functional models are explained. In addition, four well-known stochastic models and a new stochastic model are presented. Two types of unknowns are used in the least-squares adjustment of functional models. One of them is the scale factor, and the other is the parameter of refraction and deviation of the plumb line. Four criteria are explained to examine the functional old and new stochastic models. The first criterion is whether or not the adjustment gives reasonable results. The other criteria are the functional model test, stochastic model test, homogeneity, and mean accuracy test. To achieve the objectives stated earlier, a leveling net located in and around Istanbul, Turkey, is used, consisting of 81 benchmarks and 76 lines. Five lines are measured using both reciprocal trigonometric leveling and valley crossing leveling. The rest are measured by the precise leveling method. The net is adjusted using the free adjustment approach along with stochastic models, which are known and suggested.
EDM-Height Traversing versus Geodetic Leveling
In the past, EDM-height traversing was rarely considered as an alternative to geodetic leveling. This paper outlines the theory of the method and investigates the attainable accuracy. In flat terra...