The present disclosure pertains to a signal processing device, a signal processing method, and a program that make it possible to easily confirm a growth state of vegetation. In the present invention: an NDVI relative value calculation unit calculates, from a vegetation index which represents a growth state of a lawn and is calculated on the basis of a sensing image, a relative value with respect to an average value of the vegetation index； and a display processing unit performs processing, on the basis of the relative value, for displaying an image representing the growth state of a subject being inspected. Further: an NDVI average value calculation unit calculates, for the entirety of the lawn, an NDVI average value in which Normalized Difference Vegetation Indices (NDVIs) representing the growth state of the lawn are averaged； and a correlation factor calculation unit calculates a correlation factor for matching the NDVI average value to a predetermined NDVI defined value. Then, the NDVI relative value calculation unit calculates an NDVI relative value that is relative to the NDVI average value by applying the correlation factor for each measurement unit in which a measurement of the lawn is performed. The present technology can be applied, for example, to a vegetation inspection device for inspecting vegetation of a lawn.La présente invention concerne un dispositif de traitement d'un signal, un procédé de traitement d'un signal et un programme qui permettent de confirmer facilement l'état de croissance d'une végétation. Dans la présente invention, une unité de calcul de valeur relative d'indice NDVI (indice de végétation par différence normalisé) calcule, à partir d'un indice de végétation qui représente l'état de croissance d'une pelouse et qui est calculé en fonction d'une image de détection, une valeur relative par rapport à une valeur moyenne de l'indice de végétation ； et une unité de traitement d'affichage effectue, en fonction de la valeur relative, un tr
