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ZAKLJUÈAK CONCLUSIONS GNSS use in forest environment that is particularly challenging to the CORS-GNSS signal reception due to multipath and direct signal blockages, which significantly affect the signal processing and further degrade the position accuracy and availability. PPK method is very efficient yet in difficult situations we are going to encounter certain accuracy problems. Forest environments should also be classified under difficulty situations. In this study the most important criteria in PPK measurement technique are survey time and fixed of the integer ambiguity value. To raise measurement reliability there, results from different resolutions of ambiguities should be used on each point. This would enhance survey reliability and accuracy. Nonetheless, it appears that forest measurements with ± 1 cm accuracy cannot be guaranteed on all occasions, since difficult situations may lead to greater errors for this study (about ± 0-10 cm accuracy for horizontal components and about ± (0-100) cm accuracy for vertical components). LITERATURA REFERENCES El-Mowafy, Ahmed 2000: Performance Analysis of the RTK Technique in an Urban Environment. https://doi.org/10.1080/00050353.2000.10558803. Kaartinen H., Hyyppä J., Vastaranta M., Kukko A., Jaakkola A., Yu X., Pyörälä J., Liang X., Liu J., Wang Y., Kaijaluoto R., Melkas T., Holopainen M., Hyyppä H. 2015: Accuracy of kinematic positioning using Global satellite navigation systems under forest canopies. Forests 6(9): 3218–3236 Pirti, A., Yucel, M.A., Gumus, K. 2013: Testing real time kinematic GNSS (GPS and GPS/GLONASS) methods in obstructed and unobstructed sites. Geodetski vestnik, 57- 83. Pirti, A. 2016: The seasonal effects of deciduous tree foliage in CORS-GNSS measurements (VRS/FKP). Tehnicki vjesnik - Technical Gazette, 23(3), 769- 774. https://doi.org/10.17559/TV-20150301214046 Pirti, A., N. Arslan, B. Deveci, O. Aydin, H. Erkaya, and R. G. Hosbas. 2009: “Real-time Kinematic GPS for Cadastral Surveying.” Survey Review 41 (314): 339–351. doi: 10.1179/ 003962609X451582 Pirti, A. 2008: Accuracy analysis of GPS positioning near the forest environment. Croat. J. For. Eng. 29(2), 189–199 Pirti A. 2005: Using GPS System near the Forest and Quality Control. Survey Review Journal 38(298): 286–298. Pirti, A., Gumus¸, K., Erkaya, H., and Gursel Hosbas¸, R. 2010: “Evaluating repeatability of RTK GPS/GLONASS near/under forest environment.” Croat. J. For. Eng., 31(1), 23–33. Wolf P.R. and C.D. Ghilani 2008: Elementary Surveying, An Introduction to Geomatics. 12th Edition, Prentice Hall Upper Saddle River, New Jersey, 960 p. Wright W.C., Wilkinson B.E., Cropper W.P. 2017. Estimating GPS Signal Loss in a Natural Deciduous Forest Using Sky Photography. Papers in Applied Geography 3(2): 119–128. URL1: https://d32ogoqmya1dw8.cloudfront.net/files/getsi/teaching_materials/high-precision/static_gnss_survey_methods.v4.pdf |