Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí lâm nghiệp đề tài: A linkage among whole-stand model, individual-tree model and diameter-distribution model. | JOURNAL OF FOREST SCIENCE 56 2010 2 84-91 Analysis of the accuracy of GPS Trimble JUNO ST measurement in the conditions of forest canopy M. Klimánek Faculty of Forestry and Wood Technology Mendel University in Brno Brno Czech Republic ABSTRACT GPS Trimble JUNO ST was tested at 16 points under forest canopy. The measurements were done on three different dates of the growing seasons in 2007 and 2008. On each date 4 recordings were measured in the length of 1 2 5 and 10 minutes with the recording frequency of 5 seconds. The resultant data were statistically evaluated by analysis of variance ANOVA both for data before corrections and for data after post-process corrections from the reference station. The tested GPS receiver reaches the average mean square error of the measurement of XY coordinates in the interval of up to m without corrections and depending on the time of observation . The error of the altitudinal Z coordinate measurement is three times the average MSE XY. The use of corrections from reference stations turns out to be ineffective. No statistically significant relationship was proved between the PDOP value and the error of measurement of the position or height and there was no significant relationship of the type of stand or stand density or the type of relief. By contrast the age of stand was statistically significant and there are higher MSE XY values in older stands depending however on the stand density. Keywords forest canopy impact GPS GPS device accuracy location precision mean square error Trimble JUNO ST The history of a satellite positioning system goes back to the 1960s when the US navy launched the Transit system. In the former USSR the Cyklon system with the same disadvantages was used as a counterweight. In the early 1970s after the experience with these systems both superpowers started to build systems of a new generation. In the USA it was the project called GPS - NAVSTAR Global Positioning System - Navigation System using Time .
