Various aspects relate to a method of detecting an inventory in a storage space. The method comprises acquiring an image comprising image data depicting at least part of the storage space and determining, for at least an area of the image, at least one product inventory area. Next, it is detected whether the image data comprised by the image area has a transition of intensity above a pre-determined threshold within a pre-determined distance. Based on the outcome of the detection, it is determined a product is present in the product inventory area if the transition of intensity within the pre-determined distance is detected. Using edge detection, no comparison of subsequently acquired images is required. If an edge is detected, a product is determined to be present on a particular location on the shelf. This determination may be executed based on one single image, rather than on two consecutively acquired images.