_Forests_**2015**, \(6\), 3218-3236; doi:10.3390/f6093218  
_forests_  
**ISSN 1999-4907**  
www.mdpi.com/journal/forests  
_Article_  
**Accuracy of Kinematic Positioning Using Global Satellite Navigation Systems under Forest Canopies**  
**[PERSON] 1,*, [PERSON] 1, [PERSON] 2, [PERSON] 1,3, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 4, [PERSON] 2 and [PERSON] 3**  
1 Finnish Geospatial Research Institute FGI, Centre of Excellence in Laser Scanning Research, Geodeetinrinnne 2, Masala FI-02430, Finland; E-Mails: [PERSON]SS] (J.H); [EMAIL_ADDRESS] (A.K.); [EMAIL_ADDRESS] (A.J.); [EMAIL_ADDRESS] (X.Y.); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (X.L.); [EMAIL_ADDRESS] (J.L.); [EMAIL_ADDRESS] (Y.W.); [EMAIL_ADDRESS] (R.K.)  
2 Department of Forest Sciences, University of Helsinki, P.O. Box 27, Helsinki FI-00014, Finland; E-Mails: [EMAIL_ADDRESS] (M.V.); [EMAIL_ADDRESS] (M.H.)  
3 Research Institute of Modelling and Measuring for the Built Environment, Aalto University, P.O. Box 15800, Aalto FI-00076, Finland; E-Mail: [EMAIL_ADDRESS]  
4 Metsateho Oy, Vernissakatu 4, Vantaa FI-01300, Finland; E-Mail: [EMAIL_ADDRESS]  
* Author to whom correspondence should be addressed; E-Mail: [EMAIL_ADDRESS]; Tel.: +358-401-920-836.  
Academic Editor: [PERSON]  
_Received: 23 July 2015 / Accepted: 9 September 2015 / Published: 16 September 2015_  
**Abstract:** A harvester enables detailed roundwood data to be collected during harvesting operations by means of the measurement apparatus integrated into its falling head. These data can be used to improve the efficiency of wood procurement and also replace some of the field measurements, and thus provide both less costly and more detailed ground truth for remote sensing based forest inventories. However, the positional accuracy of harvester-collected tree data is not sufficient currently to match the accuracy per individual trees achieved with remote sensing data. The aim in the present study was to test the accuracy of various instruments utilizing global satellite navigation systems (GNSS) in motion under forest canopies of varying densities to enable us to get an understanding of the current state-of-the-art in GNSS-based positioning under forest canopies. Tests were conducted using several different combinations of GNSS and inertial measurement unit (IMU) mounted on an all-terrain vehicle (ATV) \"simulating\" a moving harvester. The positions of 224 trees along the driving route were measured using a total-station and real-time kinematic GPS. These trees were used as reference items. The position of the ATV was obtained using GNSS and IMU with an accuracy of 0.7 m (root mean squared error (RMSE) for 2D positions). For the single-frequency GNSS receivers, the RMSE of real-time 2D GNSS positions was 4.2-9.3 m. Based on these results, it seems that the accuracy of novel single-frequency GNSS devices is not so dependent on forest conditions, whereas the performance of the tested geodetic dual-frequency receiver is very sensitive to the visibility of the satellites. When post-processing can be applied, especially when combined with IMU data, the improvement in the accuracy of the dual-frequency receiver was significant.  
GNSS; accuracy; forest mapping; forest inventory; positioning; harvester; forest technology +
Footnote †: journal: Journal of LaTeX Templates