Development Solutions of Riga City Local Geodetic Network

Throughout the centuries, Riga has been the city with dynamic development. Its territory has unceasingly expanded, whereby previously unused territories have been urbanized. Managers of the city understood already at the end of 19th century that unified geodetic network had great importance in the development of the city. Since then, Riga’s local geodetic network has evolved with the city, several coordinate and height systems have been replaced, but the task has remained the same – to provide a flawless, homogeneous geodetic foundation for various surveying activities. In 2018, the development of the local geodetic network in several parts of the city was completed, whereby the problem arose – altitude values of surveyed terrain points determined by using the improved geodetic network did not coincide with altitude values determined using the GNSS method. Considering the above-mentioned problem, the objectives of this study were set: to plan and carry out control measurements of the improved local geodetic network in the vicinity of Grizinkalns, to provide analysis of the obtained results and recommendations for further development of a local geodetic network. The difference between the heights determined by the geometric levelling method and the heights determined by the GNSS method shall not exceed 2 mm. According to the GNSS method, using the quasi-geoid model LV’14 v2, the determined heights of the geodetic grid points differ from the given ones by 0.062 m on average. The differences are systematic. To overcome these differences, the quasi-geoid model needs to be refined.