Soil samples submitted for laboratory testing are classified into five categories according to sample quality. The greatest number of soil parameters can be determined from a category 1 sample, while category 5 samples allow for the determination of the fewest soil parameters. The quality of the sample depends on the method of sample collection.

Samples are collected using auger drilling, core drilling, or sampling cylinders. These sampling methods can also be combined to obtain the most suitable sample, depending on the types of soil layers, the depth of investigation, and the intended purpose of the planned construction.

Disturbed soil samples are collected using an auger. Such samples are suitable only for general soil descriptions (category 5 samples), to help determine how further sampling should be organized. In contrast, undisturbed soil samples are obtained by core drilling or with sampling cylinders and allow for the determination of the widest range of geotechnical parameters.

Soil sampling during drilling is often combined with soil probing.