Line plot survey is a systematic sampling technique used on land surfaces for laying out sample plots within a rectangular grid to conduct
forest inventory or agricultural research. It is a specific type of
systematic sampling In survey methodology, systematic sampling is a statistical method involving the selection of elements from an ordered sampling frame. The most common form of systematic sampling is an equiprobability method.
In this approach, progression through ...
, similar to other statistical sampling methods such as
random sampling, but more straightforward to carry out in practice.
[Aver,T.E. and H.E. Burkhart. 2002. Forest Measurements. 5th Ed. McGraw-Hill. New York. 456 p.]
This survey methodology is typically used to collect information about seedlings, shrubs, invasive species, signs of wildlife, need for fertilization, timber species count, and other similar types of data. For statistical control, all sample plots are a precise radius, typically , and must not include features outside each sampling circle.
Method
The method is commonly used for forest inventories. It makes it possible to accurately estimate the volume standing in a forested tract without counting every single item. Inventory specialists set up a line bearing on their
hand compass and determine how many plots to take on this survey line. This is done by determining the distance between survey lines (B), the distance between plots (D), and the surface area (A) of the tract. The number of samples that should be taken is then calculated as follows:
:
The survey starts with the surveyor selecting two random numbers between
and Band
and Dfor the first plot and line location. The surveyor then measures the length to the first plot, surveys, and repeats the procedure. Once at the boundary, the surveyor turns 90° and continues on to the next transect.
Uses
The line plot survey has the advantage of ensuring the inventory incorporates an even outlay and includes everything in the forested tract. Examples of this are stand regeneration surveys to assess what is growing in a forest. Transect
azimuth
An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north.
Mathematicall ...
of 300° using plots one
chain
A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...
apart in one tenth acre then perhaps moving four chains to the next plot while still on the 300° (degree) bearing.
References
{{Forestry
Forest modelling