A collateral damage estimation (CDE) is conducted for all pre-planned targets by qualified targeteers who are trained to carry out this process. For targets where there is an obvious risk of collateral damage, a computer-based collateral damage model (CDM) is used, as a guide to military judgment, to determine the estimated effects of a range of weapons against differing structures in a variety of locations (rural, semi-rural, urban, etc). When it is not operationally feasible to conduct a full and formal CDE, Commanders must still apply the basic principles of the Laws of Armed Conflict (Distinction, Discrimination, Proportionality and Necessity).