Over the past two decades, various numerical methods of analysis have become popular in the field of geotechnical engineering. However the accuracy of numerical analyses varies considerably, primarily because of the uncertainteis involved in modelling complex geological formations with the complex geomechanical characteristics of soils and rocks. Field measurements carried out during construction can be used to overcome this difficulty. The author reviews ways of using measurement results to improve numerical analyses, including the determination of a "hazard warning level" for each measurement item prior to the start of construction.