Vertical point sampling with a digital camera: Slope correction and field evaluation
Conducting vertical point sampling with a camera on sloping terrain leads to bias. We developed a computer program that adjusts for the slope at each point. This method maintains unbiased estimates, regardless of slope. Using field data we quantified the bias incurred for ignoring slope altogether. Bias will be negligible when the majority of slopes are 35 or less.
forest inventory probability proportional to size sampling point double sampling forest structure