Abstract
Global navigation satellite systems (GNSS) can quickly, efficiently, and accurately provide precise coordinates of points, lines, and surface elements, plus complete surveys and determine various boundary lines in forest investigations and management. The system has become a powerful tool for dynamic forest resource investigations and monitoring. GNSS technology plays a unique and important role in estimating timber volume, calculating timber cutting area, and determining the location of virgin forest roads and individual trees in forests. In this study, we quantitatively analyzed the influence of crown size and observation time on the single-point positioning accuracy of GNSS receivers for different forest types. The GNSS located single points for different forest types and crown sizes, enabling the collection of data. The locating time for each tree was more than 10 min. Statistical methods were used to analyze the positioning accuracy of multi-epoch data, and a model was developed to estimate the maximum positioning errors under different forest conditions in a certain positioning time. The results showed that for a continuous positioning time of approximately 10 min, the maximum positioning accuracies in coniferous and broadleaf forests were obtained, which were 12.13 and 15.11 m, respectively. The size of a single canopy had no obvious influence on the single-point positioning error of the GNSS, and canopy density was proven to be closely related to the positioning accuracy of a GNSS. The determination coefficients (R2) in the regression analysis of the general model, coniferous forest model, and broadleaved forest model that were developed in this study were 0.579, 0.701, and 0.544, respectively. These results indicated that the model could effectively predict the maximum positioning error in a certain period of time under different forest types and crown conditions at middle altitudes, which has important guiding significance for forest resource inventories and precise forest management.
Highlights
The positioning errors in both the coniferous and broadleaved forests decreased as the positioning time increased, which indicates that increases in positioning time help improve the accuracy of single-point positioning
The results of this study showed that the positioning error of a single point was relIn this study, single-point were obtained thefound
The results were compared with reference coordinates positioning accuracy of a Global navigation satellite systems (GNSS) is strongly affected by stand density and canopy size measured with a total station, and the influences of different forest types, positioning single-point positioning under a coniferousFinally, forest and a time, andThe crown sizeperformed on the single-point positioning accuracy were determined
Summary
Many forest resource surveys require highly accurate field measurements of the spatial locations of trees. According to the different requirements of practical applications, the accuracy of locating a single tree or sample site varies from several centimeters to several meters [1]. With increasing attention focused on the spatial locations of trees and sample plots in forestry surveys, exploring which factors are the dominant factors affecting spatial positioning and determining how to quantitatively express the impact of those factors on positioning accuracy are becoming necessary [2,3]. The development of satellite positioning is rapidly providing new options for forest resource managers to obtain timely and highly accurate location data [4].
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