A surveillance sensor system for a surveillance network, said surveillance sensor system being configured to monitor an environment surrounding a device, and comprising: a processing unit, a tridimensional sensor and a camera mounted on the device and each one adapted to communicate with the processing unit, wherein the processing unit is: receiving a first stream comprising a plurality of N point cloud frames from a tridimensional sensor having a first field of view, each point cloud frame comprising a set of tridimensional data points acquired by said tridimensional sensor, said tridimensional data points being representative of features located in the environment, the features being distinct elements in the environment, receiving a second stream comprising a plurality of M images from the camera having a second field of view, each image being a matrix of pixels having color values corresponding to sensed light from same features located in the environment, wherein the first field of view and the second field of view intersecting in the environment substantially at the location of the features, and wherein the time instants of the point cloud frames and the time instants of the images are included into a common time period in which the data from first and second streams are analysed, generating a global tridimensional map by merging the tridimensional data points of the plurality of N point cloud frames, detecting a plurality of features in the plurality of M images by processing said images, associating to each feature of the plurality of features, the tridimensional data points in the global tridimensional map belonging to said feature, wherein the associating of a feature to tridimensional data points is processed by projecting each tridimensional data point into a projected pixel in the images, and by determining if a projected pixel in an image can correspond to a feature detected, on the bases of a proximity criterion that minimizes a distance between the projected pixel and the feature detected in the image, determining properties of each feature of the plurality of features on the basis of the M images and the tridimensional data points associated to said feature, and providing to the surveillance network, the global tridimensional map, the plurality of features including the association of said features to the corresponding tridimensional data points in the global tridimensional map, and including the properties determined for each feature, and the processing unit is not providing the images from the camera to the surveillance network, the processing unit discarding or erasing the images after a predetermined amount of time. a processing unit, a tridimensional sensor and a camera mounted on the device and each one adapted to communicate with the processing unit, receiving a first stream comprising a plurality of N point cloud frames from a tridimensional sensor having a first field of view, each point cloud frame comprising a set of tridimensional data points acquired by said tridimensional sensor, said tridimensional data points being representative of features located in the environment, the features being distinct elements in the environment, receiving a second stream comprising a plurality of M images from the camera having a second field of view, each image being a matrix of pixels having color values corresponding to sensed light from same features located in the environment, wherein the first field of view and the second field of view intersecting in the environment substantially at the location of the features, and wherein the time instants of the point cloud frames and the time instants of the images are included into a common time period in which the data from first and second streams are analysed, generating a global tridimensional map by merging the tridimensional data points of the plurality of N point cloud frames, detecting a plurality of features in the plurality of M images by processing said images, associating to each feature of the plurality of features, the tridimensional data points in the global tridimensional map belonging to said feature, wherein the associating of a feature to tridimensional data points is processed by projecting each tridimensional data point into a projected pixel in the images, and by determining if a projected pixel in an image can correspond to a feature detected, on the bases of a proximity criterion that minimizes a distance between the projected pixel and the feature detected in the image, determining properties of each feature of the plurality of features on the basis of the M images and the tridimensional data points associated to said feature, and providing to the surveillance network, the global tridimensional map, the plurality of features including the association of said features to the corresponding tridimensional data points in the global tridimensional map, and including the properties determined for each feature, and the processing unit is not providing the images from the camera to the surveillance network, the processing unit discarding or erasing the images after a predetermined amount of time.