Degradation of GNSS Accuracy by Multipath and Tree Canopy Distortions in a School Environment: A Recent Study

Accurate position determination using GNSS technology necessitates an unobstructed view of the sky. However, it has been observed that control stations established using the GNSS technique for surveying/research projects no longer produce the desired accuracy after a few years. This could be due to environmental features (buildings, fences, trees, and so on) sprouting around them as a result of infrastructure development and urbanization. With increased use of GNSS in urban and tree canopy environment setting, there is a need to understand the accuracies achievable in such landscapes. Most previous GNSS evaluations have been performed under “clear sky” conditions, where views to satellites are unobstructed. This study investigates the extent of degradation of accuracy at fifteen stations located within a school environment. The study was done by comparing GNSS fixes of those stations with their corresponding positions determined in a total station (electronic tacheometer) survey. The latter was used as a study control because it is unaffected by the monitored environmental features and factors. The study revealed that some of the stations are no longer suitable for the GNSS technique (GDOP is too high (171.6), while others’ GNSS-derived positions differed from those of the total station by up to 5.7m. As a result, all controls were reclassified in accordance with national and international accuracy standards. We also recommend that such checks and reclassification be performed on existing controls on a regular basis.

Author (S) Details

Dr. Victus N. Uzodinma
Department of Geoinformatics and Surveying, University of Nigeria, Enugu Campus, Nigeria

Uchechukwu Nwafor
Department of Geoinformatics and Surveying, University of Nigeria, Enugu Campus, Nigeria.

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