Photographic slides of the ground surface are taken and the ground cover measured by projecting the image onto a grid to determine area. More recently computers have been used to analyze these images. A major disadvantage of this method is the long delay in getting an answer. In general, field sampling to determine residue cover involves selection of a set of sampling locations and then evaluation of cover at these locations. The line transect this type of method.
Ground cover is evaluated at points along a line.
This procedure is valid provided that a sufficient number of points are observed and that they are separated by a reasonable distance. Points do not necessarily have to be of uniform separation. Random intervals are equally valid, although less convenient. The line transect is simply a convention to observe a number of points. Ground cover is determined by counting the number of points that intersect residue.