1. Introduction

The problem of how to search for a moving target arises every day. Search problems arise in military, rescue, law enforcement, and border patrol operations. In military operations, the searchers may be aircraft looking for suspected individuals or downed pilots in an area of interest. The U. S. Navy has a long history of planning searches for adversarial submarines. Park rangers may search for lost hikers. Almost every day someone is lost in a wilderness or rural area, and volunteer search and rescue groups plan and execute searches to find them – Koester (2008). In a damaged or burning building, fire fighters and ground robots may search for trapped individuals. Law enforcement officers may act as searchers when looking for criminals. Near national borders, the searchers may be border patrols seeking illegal immigrants. The searchers may also be Coast Guard cutters and helicopters scanning the ocean for smugglers.