Files
Abstract
Thanks to recent developments in GNSS technologies, affordable consumer-grade GNSS receivers have been available for use in general forest activities. Especially, non-traditional consumer-grade GNSS receivers, which include smartphones and GPS watches, have garnered attention due to their usability and price range. However, there are still knowledge gaps regarding the positional error of non-traditional consumer-grade GNSS receivers, its effect on spatial point pattern analysis, and how nearby environmental conditions influence positional error. Therefore, three studies were developed to address this knowledge gap. The first study investigated the positional accuracy of a GPS watch by comparing it to a mapping-grade GNSS in different forest types, seasons, and meteorological conditions. The positional accuracy of the GPS watch was not significantly different in different forest types but was significantly different across seasons. The GPS watch provided a similar level of positional accuracy as the mapping-grade GNSS receiver during the leaf-off season. This study also confirmed a weak but significant correlation between positional accuracy and meteorological conditions (air temperature and absolute humidity). The second study was conducted to evaluate the feasibility of common methods to establish tree locations, and used spatial point pattern analysis to assess whether the pattern of trees in a forest, described by GNSS data, was consistent with the original pattern of trees. This study confirmed that spatial information of trees collected by GNSS technology, without offending practicality of the data collection effort, failed to represent the original point pattern of trees in a real-world environment. This study also suggested that the inherent positional error of GNSS receivers might then mislead the results of spatial point pattern analysis if data are collected using normal field data collection protocols. The third study was conducted to assess the effect of nearby forest variables on positional accuracy of data collected by GNSS receivers. Correlation analysis was used to determine whether positional accuracy of data collected by various GNSS receivers was based on the vicinity and size of nearby trees. Some of statistically significant correlations were observed, but it was confirmed that the problem may be much more complicated to allow a generalization of the effects of forest conditions on positional accuracy, as the results were not consistent across GNSS receivers tested. Results of these studies expand upon the possibilities and limitations of using consumer-grade GNSS receivers in forested areas without significant augmentation methods.