Line sampling

Introduction

Line sampling uses one-dimensional lines as observation units, just as we may use for many purposes fixed area sample plots (two-dimensional observation units) or points (dimensionless observation units). Line sampling does here not refer to the so-called transects which usually mean elongated narrow strips, that is: two-dimensional plots. Depending on the dimensionality of the observation units, different types of observations can be made on them. There are three major uses of line sampling:

• It may be observed which portion of a sample line comes to lie in forest. These portions can be used to estimate the forest cover percent. This type of sampling is called line intercept sampling.

• It may be observed how many times a sample line intersects with a line feature in the landscape such as forest edges, roads or creeks. The number of intersections can be used to estimate the total length of these line features. This type of sampling is called line intersect sampling.

• It may be observed whether a population element is intersected or not by a sample line. By this, we may use the line samples to make a random selection of population elements in the absence of an a priori sampling frame.

A good reference for line sampling is deVries (1986) or earlier related studies by deVries.