Geometric and Statistical Assessments on Horizontal Positioning Accuracy in Relation with GNSS CORS Triangulations of NRTK Positioning Services in Thailand

Thailand has implemented GNSS Continuously Operating Reference Stations (CORS) and Network Real-Time Kinematic (NRTK) Positioning services collaborated by several government agencies and universities for various applications. This research includes 114 GNSS CORSs; providing 143 triangle loops and covering 63 provinces nationwide, to determine and analyse the obtained horizontal positioning accuracy and their ground station geometries. Triangulation networks are categorised in terms of shapes and baseline distances. Well- and ill-conditioned triangles are defined in accordance with different baseline lengths. The horizontal positioning accuracy is computed using static and NRTK positioning determinations whilst static positioning results are defined as the ground truth. Student's T tests are used to ensure the significance of calculated results according to each test case. The results show obtained horizontal positioning accuracies are within the specified accuracy of less than 4 centimetres and do not show any significant differences based on the defined significant level of 0.05. This GNSS CORS triangulation network geometry scheme does not influence the computed horizontal positioning accuracy obtained from NRTK-Virtual Reference Station (VRS) GNSS positioning services; however, the positioning accuracy is still directly due to distances between nearest GNSS CORS or its triangulation network, therefore, further suggestions are provided.