Assessment of Low-Cost GPS Receiver Accuracy and Precision in Forest Environments

Abstract

Selecting the appropriate receiver is an issue when a major portion of global positioning system ͑GPS͒ data collection is below forest canopies. This study compares four low-cost GPS receivers, in order to determine the most suitable receiver for position assessment under different forest canopy covers, in terms of ease of use, accuracy, and reliability. A total of 33 positional assessments were gathered per receiver, plot, and method, in 18 forest locations. Data were described and analyzed through a sample comparison analysis at 95% confidence level ͑Mann-Whitney nonparametric test͒, in order to determine the existence of differences in accuracy and precision in positioning between receivers. Results showed that there were significant differences between the receivers regarding accuracy and precision measuring coordinates; moreover, accuracies were different depending on the canopy cover and forest characteristics. Therefore, practical recommendations for each case were settled in order to help foresters to select the most suitable receiver. Moreover, key forest variables regarding GPS performance were identified, so that forest environments could be effectively clustered by them.

Mapeamento da Araucaria angustifolia utilizando receptores GPS

“…Na área florestal, a tecnologia GPS tem tido diversas aplicações, tais como: instrumento de atualização de bases cartográficas de empresas florestais e locação de experimentos ambientais (RODRIGUES-PEREZ et al, 2006), na localização e marcação de árvores em inventário florestal (FIGUEIREDO et al, 2008), no mapeamento simultâneo das árvores e das colheitadeiras (harvesters) florestais (OHMA et al, 2007), no mapeamento e danos causados por incêndios florestais (EL-SHEIMY & WRIGHT, 2003) e no microplanejamento florestal (BERNARDI & PONTES, 2006). Naesset (2001) comentou que a precisão dos resultados nas determinações de posicionamento depende do procedimento utilizado e do aparelho receptor GPS usado e como resultado pode-se obter precisão de 10 metros (posicionamento absoluto) até milímetros (posicionamento usando sinais L1 e L2).…”

Monitoring of Forest Hauling Roads Wearing Course Damage Using Unmanned Aerial Systems

“…However, they added that this method can also be inaccurate in the forest. Rodriguez-Perez et al (2007) pointed out that the use of GPS in the forest ecosystem introduces problems related to signal reception under the forest canopy, including the visibility of satellites in a given territory at the time of measurement. Coulter et al (2006) were convinced that the best method to set the maintenance plan of a forest road network is a combination of heuristic analysis, analysis of financial costs and impacts on the environment, and "expert judgment".…”

Impact of rainfall intensity and cutslope material on sediment concentration from forest roads in northern Iran

“…The main factors that cause increased sediment delivery to forest streams are removing plant cover along the forest road pathway, compaction of the soil in the roadbed, interception of surface and sub-surface flows, constructions of cutslopes, and alteration of hillslope water pathways (Tague & Band 2001). Sediment delivered to forest streams cause water resource pollution, filling dams and may have impacts on aquatic habitat (Damian 2003, Refahi 2006, Khalilpoor et al 2008.…”

“…The main factors that cause increased sediment delivery to forest streams are removing plant cover along the forest road pathway, compaction of the soil in the roadbed, interception of surface and sub-surface flows, constructions of cutslopes, and alteration of hillslope water pathways (Tague & Band 2001). Sediment delivered to forest streams cause water resource pollution, filling dams and may have impacts on aquatic habitat (Damian 2003, Refahi 2006, Khalilpoor et al 2008.Three methods are typically used to measure sediment produced from forest roads: (1) measurement in natural conditions with natural precipitation events (e.g., direct measurements from outlet of live streams culverts or using sediment traps - (2007) showed that cutslope areas are responsible for about 9% of the total road segment sediment production. Luce & Black (1999) examined the relationship between sediment production and road attributes such as distance between culverts, road gradient, road texture, and vegetation cover on cutslope.…”