MODEL RELEASED. Different transect methods. Students carrying out a survey of the plants in a grassy area by combining two different transect methods. The quadrat transect (square grid) is being used at intervals along a line transect (straight line). The student at left is counting the number of plants in a particular grid location, and the student at right is recording the results. The use of such transects, together with probability theory, allows entire populations of plants in a field to be estimated from a survey of a few small areas.