Above-water monitoring of swimming pools

A method for monitoring swimming pools for possible drowning victims, the method comprising:

• a) forming a sequence of digital images of a pool, each image being formed by a passive sensor positioned above a surface of the pool, the sensor comprising means for receiving an image of an object located at or below the surface of the pool,
• b) analyzing said images to determine whether the mages indicate a presence of a drowning victim in the pool, and
• C) alerting an operator of the presence of a drowning victim,
• wherein step (b) includes passively compensating for refraction of images caused by a roughened water surface due to surface waves in the pool, wherein the water surface defines a plurality of areas having different refraction properties,
• wherein step (b) includes:
• d) decomposing each image into principal components,
• e) analyzing each image component produced in step (d) to detect predetermined shapes in said image component, and
• f) analyzing sequences of image components obtained from step (e) to detect predetermined movements of said predetermined shapes in said sequences of image components,
• wherein said predetermined shapes are selected to the human forms, and wherein said predetermined movements are selected form the group consisting of vertical movements and vertical movements with rotation.

A method of monitoring a pool so as to detect possible drowning victims therein, the method comprising:

• a) forming a sequence of digital images of a pool, each image being formed by a passive sensor positioned above a surface of the pool, the sensor comprising means for receiving an image of an object located at or below the surface of the pool,
• b) decomposing each image into principal components so as to enhance quality of said images,
• c) analyzing at least some principal components obtained from step (b) to detect a presence of predetermined shapes in said image,
• d) analyzing sequences of images having been found to be likely to contain said predetermined shapes, to detect predetermined movements associated with drowning, wherein the analyzing steps include passively compensating for refraction of images caused by a roughened water surface due to surface waves in the pool, wherein the water surface defines a plurality of areas having different refraction properties, and
• e) alerting an operator of the existence of a possible drowning event when said predetermined movements are detected.