1. Introduction

The design components of a sample based inventory can be subdivided into (1) sampling design, (2) response design and (3) estimation design, following a logical and also a temporal order. In this subject paper we are concerned with the response design, sometimes also called observation design and we deal with the question: how are observations and measurements made on the population elements that have been selected from the population by the sampling design. Estimators are then applied to the set of observed values producing eventually estimations as results of the sampling study (estimation design).

In National Forest Assessments (NFAs), measurements and observations are made in several contexts: in maps, in aerial photographs, in satellite imagery, in the field. While this subject paper focuses on measurements in the field, the general observations on data quality and measurement strategies do also hold for any other measurements.