1. A computer-implemented image analysis process for making animal measurements, including: accessing image data representing an image including an animal object representing an animal; identifying coordinate values for a surface boundary of said animal object; selecting one or more start points on the surface boundary, wherein selecting the start points includes determining whether two or more potential start points correspond to a predefined expected animal shape; generating surface boundary data, representing at least a portion of the surface boundary, using a gradient of surface boundary coordinate values starting at each of the selected one or more start points; generating distance data representing distances between a plurality of boundary locations on the surface boundary, using the surface boundary data; generating size data, representing the animal's size, using the distance data; and generating weight data, representing a weight of the animal, based on the size data, including accessing weight model data representing a predetermined weight model which associates size values with weight values for the animal.