Get/set similarity score threshold.

Namespace:  SourceAFIS.Simple
Assembly:  SourceAFIS (in SourceAFIS.dll)


Visual Basic (Declaration)
Public Property Threshold As Single
public float Threshold { get; set; }
Visual C++
property float Threshold {
	float get ();
	void set (float value);
function get_threshold();
function set_threshold(value);

Field Value

Similarity score threshold for making match/non-match decisions. Default value is rather arbitrarily set to 25.


Matching algorithm produces similarity score which is a measure of similarity between two fingerprints. Applications however need clear match/non-match decisions. Threshold is used to turn similarity score into match/non-match decision. Similarity score at or above Threshold is considered match. Lower score is considered non-match. This property is used by Verify(Person, Person) and Identify(Person, IEnumerable<(Of <<'(Person>)>>)) methods to make match decisions.

Appropriate Threshold is application-specific. Application developer must adjust this property to reflect differences in fingerprint readers, population, and application requirements. Start with default threshold. If there are too many false accepts (SourceAFIS reports match for fingerprints from two different people), increase the Threshold. If there are too many false rejects (SourceAFIS reports non-match for two fingerprints of the same person), decrease the Threshold. Every application eventually arrives at some reasonable balance between FAR (false accept ratio) and FRR (false reject ratio).

See Also