Özet:

GNSS technology has become a powerful tool for researching and monitoring forest resources. However, forest cover has a negative impact on GNSS signals and satellite availability in woodland areas, which may make it difficult to determine a position with high accuracy. The Precise Point Positioning (PPP) technique, which allows for centimeter-level positioning in open areas using only a GNSS receiver, has gained considerable interest due to advancements in satellite geodesy and analysis techniques. In this study, the effect of different observation durations (1, 2, 4, and 6 hours), sampling rates (30, 60, and 120 seconds), and satellite data (GPS-only and GPS+GLONASS) on the accuracy of static PPP-AR (Ambiguity Resolution) solutions in woodland areas was investigated. GNSS measurements were conducted at two different locations (open and woodland areas) on the Yeşilırmak Campus of Amasya University. The canopy closure ratio of the woodland area was determined to be approximately 56% using i-Tree Canopy software. The collected observation data was sent to the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) online evaluation software, which is capable of performing static PPP-AR solutions. The results were showed that using the PPP-AR technique in woodland areas, the position can be determined with an accuracy of about 10 centimeters with a 2-hour observation duration. In addition, it was observed that generally GPS+GLONASS results perform better than GPS-only results and selecting a high sampling rate did not have a significant impact on the results.

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