—In this paper we present a system that integrates automatic camera geometry estimation and object detection from a Pan Tilt Zoom camera. We estimate camera pose with respect to a world scene plane in real-time and perform human detection exploiting the relative space-time context. Using camera self-localization, 2D object detections are clustered in a 3D world coordinate frame. Target scale inference is further exploited to reduce the number of false alarms and to increase also the detection rate in the final non-maximum suppression stage. Our integrated system applied on real-world data shows superior performance with respect to the standard detector used. Keywords-person detection; PTZ camera; context; structure from motion; SVM;