Dear Sparch,
There are. The newest release of OrthoGraph Architect (1.1.1) supports imperial untis.
To set the measurement please go to the Settings page of you iPad. There you will find OrthoGraph as one application from the list. If you select it, then you will be able to set the measurements to Imperial. Please don't forget to restart OrthoGraph after switching the units. The measurments done with OrthoGraph will also be displayed in imperial units after this change, you won't loose any data.