This paper offers a novel means of determining principal strain fields within a strain-driven environment and visualising them to inform the behaviour. Many practicing geotechnical engineers are familiar with stress fields, and stress-driven environments, whereas the issue here is that of a strain field in a strain-driven environment, which may be considered somewhat unusual. The example provided relates to the strain-driven environment produced by underground coal mine subsidence in the Southern Coalfield of New South Wales, though the principle applies to other strain-driven environments. The method borrows the use of constant strain triangle theory based on shape functions from Finite Element theory. Triangles allow regional distributions in strain fields to be developed.