ASSESSMENT OF THE NEED FOR GROUND CONTROL POINTS IN AERIAL SURVEYS FOR ESTIMATING THE VOLUME OF STACKED TIMBER

Abstract

Background: Our study aimed to investigate the feasibility of conducting aerial surveys without ground control points to estimate the volume of wood piles in planted areas. The data used in this study include both manual measurements (conventional method) and aerial imagery of 24 wood piles composed of Eucalyptus sp. The aerial surveys were conducted based on two flight plans: one performed at a flight height of 50 meters above the ground, with frontal and lateral overlaps of 70%, and other one conducted at a flight height of 80 meters above the ground, with frontal and lateral overlaps of 80%. Thirty-five ground control points (GCPs) were considered. Friedman and Nemenyi tests were applied to evaluate whether there were significant differences between the wood stockpile volume estimates obtained by the conventional method and those derived from the different surveys, with and without GCPs.

Results: The processing with the use of GCPs resulted in smaller RMSE values compared to those without GCPs. The volume estimates for each wood stockpile were similar, regardless of the presence or absence of GCPs. The Friedman test yielded a p-value of 0.3796, indicating that there is no evidence to suggest significant differences between the values obtained by different methods.

Conclusion: The use of control points did not significantly improve the accuracy of volume estimates for wood piles placed in the field. Under the analyzed conditions, a low-cost drone can be used to estimate the volume of wood piles in the field without the need for ground control points.