Analiza precyzji i dokładności pomiarów GPS w warunkach leśnych

Analysis of precision and accuracy of GPS measurements in forest conditions

• Polish
• English

The paper presents results of GPS measurements executed in forest conditions. The GPS measurements were made with the use of dual-frequency Ashtech Z-Xtreme receivers. The test measurements were performed in the forest at the University of Warmia and Masury in Olsztyn. Two different analyses were conducted: Real Time Positioning (RTK) and post-processing data elaboration. Postprocessing GPS data were elaborated with the use of Ashtech Office Suite (AOS) software. After very careful study of static elaborations centimeter accuracy was achieved, though large errors (a few meters) could occur. Gross errors were caused by heavy obstructions due to tree canopy. It caused frequent losses of contact with satellites as well as multipath errors. Similarly in the case of RTK measurements thanks to multiple initialization of ambiguity resolution centimeter accuracy was also obtained. However, GPS/RTK measurements demand large experience in GPS elaboration as well as very thorough knowledge of GPS positioning. Very important issue is careful planning of GPS sessions as well as applying appropriate GPS receiver sets. Future combination of GPS and GLONASS with GALILEO systems will bring considerable improvement in getting reasonable results in forest conditions, especially RTK positioning seems very costeffective in forest conditions.