Abstract
Real-time positioning on mobile devices using global navigation satellite system (GNSS) technology paired with radio frequency (RF) transmission (GNSS-RF) may help to improve safety on logging operations by increasing situational awareness. However, GNSS positional accuracy for ground workers in motion may be reduced by multipath error, satellite signal obstruction, or other factors. Radio propagation of GNSS locations may also be impacted due to line-of-sight (LOS) obstruction in remote, forested areas. The objective of this study was to characterize the effects of forest stand characteristics, topography, and other LOS obstructions on the GNSS accuracy and radio signal propagation quality of multiple Raveon Atlas PT GNSS-RF transponders functioning as a network in a range of forest conditions. Because most previous research with GNSS in forestry has focused on stationary units, we chose to analyze units in motion by evaluating the time-to-signal accuracy of geofence crossings in 21 randomly-selected stands on the University of Idaho Experimental Forest. Specifically, we studied the effects of forest stand characteristics, topography, and LOS obstructions on (1) the odds of missed GNSS-RF signals, (2) the root mean squared error (RMSE) of Atlas PTs, and (3) the time-to-signal accuracy of safety geofence crossings in forested environments. Mixed-effects models used to analyze the data showed that stand characteristics, topography, and obstructions in the LOS affected the odds of missed radio signals while stand variables alone affected RMSE. Both stand characteristics and topography affected the accuracy of geofence alerts.
Highlights
Our first null hypothesis was that neither forest stand characteristics, topography, nor the presence of obstructions in the line-of-sight affected the probability of successful radio signal propagation between global navigation satellite system (GNSS)-radio frequency (RF) units
The odds of a missed signal decreased by a factor of 0.93 per unit increase in total distance of vegetation (TVi) (p = 5.65 × 10−7), while the odds of a missed signal increased by a factor of 1.10 per unit increase in TPHÃ0.01 (p = 1.45 × 10−3)
Analysis of missed radio signals indicated that forest stand characteristics, topography, and LOS obstructions affected the odds of missed signals
Summary
The purpose of this study was to characterize the factors affecting real-time positioning on irregular, forested terrain through analysis of the effects of forest stand characteristics, topography and other line-of-sight (LOS) obstructions on the GNSS accuracy and radio signal propagation quality of multiple Raveon Atlas PT GNSS-RF transponders (Raveon Technologies, Vista, California, USA) functioning as a network. Our first null hypothesis was that neither forest stand characteristics, topography, nor the presence of obstructions in the line-of-sight affected the probability of successful radio signal propagation between GNSS-RF units. Our third null hypothesis was that neither stand characteristics, topography, nor physical obstructions affected the time-to-signal accuracy of geofence crossings We tested this by using linear mixed-effects models to determine which factors most affected geofence intersection alert delay
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