There are many kinds of surveillance equipment for monitoring visual, auditory and communications data. Some are widely available; others are legally or financially out of reach of anyone except government agencies. Technology is not limited simply to tools for gathering information, but extends to systems for interpreting data and evaluating patterns. Each kind has particular uses and limitations. Purposes of surveillance include detection of wrongdoing, crime prevention, safety, scientific research, personal security and public safety.
Digital cameras continue to offer ever-increasing capability in smaller packages for lower cost. Coupled with the greater ease with which digital imagery may be analyzed and manipulated, this has led to the steady decline of analog cameras for most purposes.