This article summarises Root Capital and Acumen's perspectives on programme and impact evaluation, and it's similarities to GPS which measures three dimensions of location (latitude, longitude, and elevation). It elaborates on how impact information also has three primary dimensions: type of impact—the nature of the impact(s) on each person or organisation; scale of impact—the number of people or organizations affected; and depth of impact—the amount or intensity of change experienced, per type of impact, per person affected.