Emergency preparedness and response systems for nuclear and radiological emergencies have to deal with decision-making in situations with relevant uncertainties. Consistent and appropriate protective measures must be decided before, during and after emergency situations. CONFIDENCE WP2 research helps to improve this decision-making process in the urgent response and the early response phase of emergency situations with potential major releases to atmosphere. This paper describes methods to reduce uncertainties in dose assessment for the population using data from stationary and mobile environmental monitoring programs. A special focus is given to identification of the measurement uncertainties of stationary and mobile monitoring systems. Methods to reduce these uncertainties and procedures to optimise mobile monitoring strategies are discussed. A first contribution towards assessing the quality of dose-rate measurements performed by the general population is made. In addition, the paper introduces approaches for advanced dose assessment tools using monitoring data and concepts for identifying critically exposed groups.