The paper proposes formal criteria and a visualisation concept to measure relative innovation in a population of design concepts. The main criterion is called the 'Configuration Distance', and is the summation of two sub-criteria called the 'Component Distance' and 'Value Distance'. The visualisation concept is called the 'Design Solution Topography', which allows visualisation of a population of design concepts in terms of their performance, Component and Value Distances. When incorporated into a conceptual designing method, being developed by the first author, the criteria will enable designers to evaluate innovation in selected designs that also satisfy the desired performance objectives at a minimum threshold or greater.