We present a method for multi-camera people detection based on the multi-view geometry. We propose to create a synergy map by the projection of foreground masks across all camera views on the ground plane and the planes parallel to the ground. This leads to significant values on locations where people are present, and also to a particular shape around these values. Moreover, a well-known ghost phenomena appears i.e. when these shapes corresponding to different persons are fused then the false detections are also generated. In this article, the first improvement is the robust detection of the candidate detection locations, namely keypoints, from the synergy map based on a watershed transform. Then, in order to reduce the false positives, mainly due to the ghost phenomena, we check if the particular shape, for an ideal person, is present or not. This shape, that is different for each location of the synergy map, is generated for each keypoint, assuming the presence of a person, and with the knowledge of the scene geometry. Finally, the real shape and the synthetic one are compared using a similarity measure that is similar to correlation. Another improvement proposed in this article is the use of unsupervised clustering, performed on the measures obtained at all the keypoints. It allows to automatically find the optimal threshold on the measure, and thus to decide about people detection. We have compared our method to the recent state-of-the-art techniques on a publicly available dataset and have shown that it reduces the detection errors.