Frankfurt Horizontal Plane
Definition
The anatomical reference plane defined by the upper border of the external acoustic meatus and the lowest point of the orbital margin (orbitale), used to standardise skull orientation in superimposition and in many anthropometric comparisons.
- Defined by
- External acoustic meatus and orbitale
- Function
- Standardises skull orientation
- Used in
- Superimposition and anthropometric comparison
- Type
- Anatomical reference plane
Common questions
Why is a standardised orientation plane necessary for photo-superimposition identification?+
Comparing a skull to an ante-mortem photograph requires matching the camera angle and head tilt in the photo to a consistent, reproducible skull position; without a fixed reference plane like Frankfurt horizontal, small orientation differences between the skull mount and photograph would produce misleading proportional mismatches.
How is the Frankfurt horizontal plane physically established when orienting a skull for examination?+
The skull is positioned, often on a craniostat or similar mount, so that the upper border of the external ear canal on each side and the lowest point of the eye orbit rim lie in the same horizontal plane, approximating the natural head position a living person holds when looking straight ahead.
Is the Frankfurt horizontal plane used only in superimposition, or does it have other forensic anthropology applications?+
It is also used more broadly in craniometric and anthropometric work, including standard skull measurement protocols and facial approximation, anywhere a consistent, comparable head orientation is needed across specimens or between a skull and a photograph.
Related terms
- Consistent with
- The categorical superimposition conclusion that examined morphological features do not exclude the skull as deriving from the same individual as the portrait....
- Exclusion
- The categorical conclusion that one or more examined features are clearly inconsistent in a way that cannot be explained by projection angle,...
- Glaister-Brash Method
- The original photographic-transparency superimposition protocol developed by John Glaister Jr and James Couper Brash for the 1935 Buck Ruxton case in Lancaster...
- Gnathion
- The most inferior point of the mandibular symphysis in the midline, corresponding to the tip of the chin in the portrait photograph....
- Gonion
- The most posterior and inferior point of the mandibular angle, bilaterally. Used in superimposition to assess the width of the jaw angle...
- Iscan-Helmer 1993
- The edited volume 'Forensic Analysis of the Skull' (Iscan and Helmer, Wiley-Liss, 1993) that brought together the first systematic reliability assessment of...
- Nasion
- The anatomical landmark at the junction of the nasal bones and the frontal bone (the bridge of the nose). One of the...
- Photo-Skull Superimposition
- The forensic identification method of placing a life portrait photograph alongside or overlaid on a photograph of a recovered skull, aligning them...
- Video Superimposition
- The updated superimposition workflow using a motorised skull turntable, a calibrated video camera, and real-time electronic mixing of the skull video image...