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Monitoring moving objects is one of the key application domains for sensor networks. In the absence of cooperative objects and devices attached to these objects, target tracking algorithms have to be used for monitoring. In this paper, we present that many of the applications of moving object monitoring systems could be addressed with low-frequency snapshot-based queries. With the realization of this query type, we show that existing target tracking algorithms may not be the least expensive solutions. We introduce an approach that uses two alternating strategies. We maintain a cheap low-quality knowledge of moving objects' location between snapshots and trigger expensive sensor readings only when a snapshot period has elapsed. With extensive experiments we show that our approach is significantly more energy efficient than established methods. It is also more effective than existing data-and-query centric in-network query processing schemes as it can maintain object identities between snapshots.