A GNSS Measurement Study Based on RTK and PPK Methods

This paper presents and evaluates two emerging methods to ensure accurate height measurements under critical conditions. The tests carried out are related to Jack Up Vessel (JUV) foundation height accuracy, and consists in making the appropriate measures in order to achieve a precise installation of an Offshore Wind Farm (OWF), based on Real-Time Kinematic (RTK) and Post-Processed Kinematic (PPK) methods. It is important to note that the OWF project is located far from the coastline, not always in the standard working range of RTK, which makes our task even more complex and restrictive. Again, it is well known in geographic positioning, that the accuracy of vertical coordinates is always more difficult to achieve than the horizontal ones, which explain the complexity of our task to define a precise height measurement of the wind turbines. For the purposes of this study, we use a Global Navigation Satellite System (GNSS) unit referred by DGPS5 (AsteRx-U), a GA830 antenna and Trimble Business Center (TBC) V5.10 software program to make post-processing. To reach a centimeter level of precision, all measures will be evaluated according to the tolerance specification of ±2.5 cm. Based on the test results and analysis, we will show the influence of the baseline lengths to achieve precise measurements and the contribution of the PPK method outside the RTK working range.