Forest Inventory Glossary

Revision as of 10:34, 30 March 2011

A

Areal sampling frame

The sampling frame or continuum (area) from which dimensionless samples points are selected.

B

Basal area

Sum of the cross sectional areas (in 1.3 meter height) of all trees per hectare (in m²/ha).

Bitterlich sampling

Or: "Angle count sampling", "relascope sampling", "point sampling". An unequal probability sampling approach (or plot design). Trees are included in a sample, if they appear bigger that a defined opening angle.

C

Cluster plot

Sample plot that is composed of unconnected sub plots. As the subplots are not selected independently, a cluster gives only one observation.

Concentric circular sample plots

See: Nested plots.

D

DBH

Diameter at breast height (1.3 meter above ground).

E

Expansion factor

Reciprocal of the inclusion probability. The factor with which observations have to be multiplied to derive an estimate of the total (or per hectare).

F

Fixed area sample plots

sample plots with defined area size.

G

H

I

Inclusion probability

Probability that a single population unit is included in a sample based on the actual plot design.

J

K

L

Line intersect sampling

A sampling design in which lines serve as observation units. Total length of linear features is estimated based on the number of intersections with sample lines.

Line intercept sampling

A sampling design with lines as observation units. Relative proportions of land use classes are estimated based on the length of sample lines (proportion) that comes to lie in a target area class.

M

N

Nested plots

Nested sub-plots of different size at one sampling location for the separate assessment of e.g. different diameter classes.

O

P

R

Random selection

A random selection of e.g. sampling locations ensures that each population unit has a positive probability to be included in a sample (or be selected as sample). See also: Simple random sampling.

S

Sample plot

A certain area or "decision rule", defining which population units are to be included at each sampling location.

Sampling design

The statistical framework or design that describes how sampling locations are selected (e.g. simple random sampling or systematic sampling).

Sampling intensity

Proportion of the population that is been sampled. In forest inventories the area proportion that was observed in the sampling study (e.g. 3% of the total area).

Sample size

Number of samples drawn from a defined sample frame.

Selection probability

Probability that a unique set of k population units is selected as sample based on the actual plot design. In case that k=1 similar to the inclusion probability.

Spatial autocorrelation

Or: "Self-correlation" describes the relationship between two observations of the same variable, taken at two different objects or times. Spatial autocorrelation refers to the correlation between observations made on plots in different distances.

Standard Error

Standard deviation of the sample means.

Stratification

A sampling technique based on the partitioning of the total population (or area) in more homogeneous sub-populations (strata) that can improve precision.

T

Total

Aggregate value of the quantitative characteristic of interest in the entire population (e.g. total volume in the area of interest).

U

V

W

X