Question

how does line transects measure abundance?

Answer 1

Since the 1930s line transect sampling method have been used to measure the abundance of the biological population. In this method, the observer moves along a transect line and mark down the location of all animals detected relative to the line. During this measurement is it generally assumed that not all animals are taken into account and the factors affecting the detectability are habitat, line and weather condition. It is also taken into account that the probability of the detection decreases with increase in distance from the line.

Let us consider D as a parameter for estimation of population abundance. X_i parameter measuring the perpendicular distance from the transect line. Let g(x) be a detection function
g(x) = P(probability of detection from a perpendicular distance x from the transect line)

f(X) = g(X) / g(t) dt ; 0 X