Abstract
During reconstruction and restoration of city geodetic networks, there is quite a common problem that is related to the nonhomogeneity of existing geodetic networks. In any city, local authorities operate with their coordinate systems. Such conditions lead to inconsistency between data of different services. There is only one way how to overcome the problem that lies in the creation and deployment of the new common coordinate system for the whole city. But such an approach has a lack connected with the necessity of transformation parameters acquisition for the latest and old coordinate systems. Insofar as old coordinate systems had been created with different accuracy, using various equipment, and measuring technologies, it is not possible to consider them as homogeneous. It means that we cannot use a classical conformal Helmert transformation to link different coordinate systems. In the presented paper were studied the different approaches for transformation parameters acquisition. A case study of the Almaty city coordinate system was researched and compared the following methods: Helmert transformation, bilinear transformation, the second and third-order regression transformation, and the fourth-order conformal polynomial transformation. It was found out that neither of the considered methods maintains the necessary transformation accuracy (>5 cm). That is why the creation of the transformation field using the finite element method (FEM) was suggested. The whole city was divided into triangles using Delaunay triangulation. For each triangle, the transformation parameters were found using affine transformation with the necessary accuracy.
Highlights
City geodetic networks are designed to provide large-scale mapping, in which the relief of the terrain and infrastructure elements are displayed with minimal distortion
When searching for the key to the local coordinate system, it is essential to find a direct transition from the planar local CS and UTM that is a derivative of the WGS84 coordinate system
The discussion centers on the transformation parameters determination of nonhomogeneous coordinate systems
Summary
City geodetic networks are designed to provide large-scale mapping, in which the relief of the terrain and infrastructure elements are displayed with minimal distortion This task is achieved by establishing and using a local 2D planar rectangular coordinate system. R. Shults et al Different approaches to coordinate transformation parameters determination. The presented study is aimed at a comparison of different approaches to coordinate transformation parameters determination of nonhomogeneous coordinate systems. To determine the distortions of the local CS of the city, it was decided to perform static GNSS measurements at the existing points of the geodetic network covering the entire territory of the city of Almaty. Despite that the coordinates in the new one system, namely UTM, were determined with considerably higher accuracy, the local authorities still demand the coordinates to be presented in both systems. Different models to coordinate transformation parameters determination were studied
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