Because mobile measurements are collected while the monitoring platform moves through the urban environment, each measurement can be associated with a specific spatial and temporal. The measured concentration can therefore be expressed as a function of location and time equation (4):

Since mobile measurements are gathered as the monitoring platform travels throughout the urban area, every measurement can be linked to a particular location and time. This means the measured concentration can be represented as a function that depends on both spatial position and temporal factors, as shown in equation (4):