Methods and apparatus to monitor environments are disclosed. Example audience measurement devices disclosed herein include means for executing a first recognition analysis on three-dimensional data representative of a first object within a threshold distance from a three-dimensional sensor. Disclosed example audience measurement devices also include means for executing a second recognition analysis on two-dimensional data representative of a second object outside the threshold distance from the three-dimensional sensor. Disclosed example audience measurement devices further include means for combining a first detection of a first person provided by the first recognition analysis and a second detection of a second person provided by the second recognition analysis to generate a people count for an environment.