Delta (Triradius)
Definition
The point of convergence of three ridge systems in a loop or whorl, visible as a Y-junction or triangular confluence. Loops have one delta; whorls have two or more; arches have none. The delta is one of the two landmarks used in Henry ridge counting and ridge tracing.
- Also known as
- Delta
- Loop pattern
- 1 delta
- Whorl pattern
- 2 or more deltas
- Use
- Reference point for Henry ridge counting/tracing
Common questions
What is the difference between a triradius and a core?+
The core is the approximate centre of the pattern's innermost recurving ridge, while the triradius (delta) is the point where three separate ridge systems converge; ridge counts and ridge tracing are measured between these two distinct landmarks.
How does the triradius support ridge tracing in whorl classification?+
An examiner traces the ridge from one delta toward the other and records whether it passes inside, outside, or meets the second delta, which is part of how whorls are sub-classified in the Henry system.
Related terms
- ACE-V
- Analysis, Comparison, Evaluation, Verification: the four-stage method for latent print examination used by accredited forensic fingerprint laboratories. Analysis examines the latent in...
- Arch
- A fingerprint pattern in which ridges flow across from one side to the other without recurving and without enclosing a central area....
- Core
- The approximate centre of a fingerprint pattern. In a loop, it is identified as the innermost recurving ridge's peak or the tip...
- Henry Classification System
- The fingerprint filing and retrieval system developed by Edward Henry with Haque and Bose in Bengal in the 1890s and adopted by...
- Level 1 Detail
- In ACE-V, the broadest level of information extracted from a fingerprint: the overall ridge flow and pattern type (arch, loop, whorl). Level...
- Loop
- A fingerprint pattern in which ridges enter from one side, recurve, and exit on the same side. The most common pattern type...
- Ridge Counting
- For loop patterns: the number of ridges crossing an imaginary straight line drawn from core to delta, excluding the core and delta...
- Ridge Tracing
- For whorl patterns: following the ridge issuing from the inner side of the left delta toward the right delta and recording whether...
- Whorl
- A fingerprint pattern in which at least one ridge makes a complete circuit around a central area, or forms a related closed...