Transection

A transect is a path along which one records and counts occurrences of the phenomenon of study (e.g. plants noting each instance).

It requires an observer to move along a fixed path and to count occurrences along the path and, at the same time, obtain the distance of the object from the path. This results in an estimate of the area covered, an estimate of the way in which detectability increases from probability 0 to 1 as one approaches the path. Using these two figures one can arrive at an estimate of the actual density of objects.

The estimation of the abundance of biological populations (such as terrestrial mammal species) can be achieved using a number of different types of transect methods, such as strip transects, line transects, belt transects, point transects and curved line transects.

New Urbanist town planners use the term transect to refer to the varieties of land use from an urban core to a rural boundary. General New Urban transect classifications (from highest to lowest density) are: urban core, urban center, general urban, suburban, rural, and natural.

Transect for counting population
Transect is also a way of sampling populations. A transect line is used for measuring the changes between at least two areas, it can not measure the population, only the changes between two areas. A transect line is useful for things like: A scientist wants to see the impact of urban cities on the average intelligence of the humans. Or: A scientist wants to know the impact of a nuclear power station to a city.

For a transect line, you need two areas, you connect them with a line and then you measure the population of the species you want to count (e.g.: intestinal bacteria). For counting them, you distribute quadrats in regular intervals on the transect line, and you count the species in those quadrats.