A precise survey, or "cracking the millimeter" is where science approaches an art form.
Application areas include dam deflection measurements, precise machine alignment, movement in large structures and assessment of the potential for rock wall collapses.
It is a field where the affects of temperature play a critical role and an understanding of the behaviour of materials under different thermal and atmospheric conditions is a prerequisite. For example, in the case of dam deflection measurements, the fixed points from which the survey is carried out have to be thermally insulated, wall temperatures in the concrete must be measured every hour, atmospheric pressure and water levels monitored continously, and so on. Special forms of mathematical bundle adjustment are necessary to take these factors into account along with the actual survey data.
Equipment calibration and independant quality control measures are critical. These surveys, paricularly in the case of machine alignment, often have to be carried out under the most hostile of conditions.