Score components in SourceAFIS transparency data
Detailed scoring, a part of algorithm transparency, is a breakdown of similarity score that is computed by SourceAFIS during matching for a pair of fingerprints. Scoring is done separately for every pairing. Pairing with the highest total score is selected as the best match.
Key | MIME | Filename in ZIP |
---|---|---|
score | application/cbor | 047-score.cbor |
score | application/cbor | 049-score.cbor |
... skipped 48 files ... | ||
score | application/cbor | 147-score.cbor |
score | application/cbor | 149-score.cbor |
Format
Scoring is recorded as a CBOR-encoded object holding several fields.
Final similarity score is stored in shapedScore
field. Other fields describe intermediate scores that contribute to the final score.
minutiaCount
- Number of matched minutiae, regardless of correctness of minutia type or accuracy of angles and distances.minutiaScore
- Score assigned forminutiaCount
.minutiaFractionInProbe
- Fraction of probe minutiae that were successfully paired, including approximate matches like inminutiaCount
.minutiaFractionInCandidate
- LikeminutiaFractionInProbe
but for candidate minutiae.minutiaFraction
- Average ofminutiaFractionInProbe
andminutiaFractionInCandidate
.minutiaFractionScore
- Score assigned forminutiaFraction
.supportingEdgeSum
- Number of supporting edges in the pairing graph.edgeCount
- Number of edges in the pairing graph, including supporting edges. This value is actually one higher than that.edgeScore
- Score assigned foredgeCount
.supportedMinutiaCount
- Number of minutiae with at least one supporting edge in addition to edges in the pairing tree.supportedMinutiaScore
- Score assigned forsupportedMinutiaCount
.minutiaTypeHits
- Number of matched minutia pairs where probe and candidate minutia have the same type (ending or bifurcation).minutiaTypeScore
- Score assigned forminutiaTypeHits
.distanceErrorSum
- Sum of distance errors, i.e. differences between probe and candidate edge length, for all edges in the pairing tree.distanceAccuracySum
- LikedistanceErrorSum
but zero at maximum tolerated distance error and increasing towards exact match.distanceAccuracyScore
- Score derived fromdistanceAccuracySum
anddistanceErrorSum
.angleErrorSum
- Sum of angle errors, i.e. differences between probe and candidate edge angles that are measured between reference/neighbor minutia direction and edge direction, for all edges in the pairing tree.angleAccuracySum
- LikeangleErrorSum
but zero at maximum tolerated angle error and increasing towards exact match.angleAccuracyScore
- Score derived fromangleAccuracySum
andangleErrorSum
.totalScore
- Total raw score computed by adding together above score components.shapedScore
- Final similarity score computed fromtotalScore
with the help of monotonic shaping function constructed in such a way as to makeshapedScore
approximately correspond to FMR (false match rate) thresholds. Increase inshapedScore
by 10 points roughly corresponds to 10x lower FMR.
Example: 047-score.cbor
{
"minutiaCount": 29,
"minutiaScore": 0.928,
"minutiaFractionInProbe": 0.6170212765957447,
"minutiaFractionInCandidate": 0.7435897435897436,
"minutiaFraction": 0.6803055100927442,
"minutiaFractionScore": 6.109143480632843,
"supportingEdgeSum": 270,
"edgeCount": 299,
"edgeScore": 79.235,
"supportedMinutiaCount": 29,
"supportedMinutiaScore": 5.597,
"minutiaTypeHits": 26,
"minutiaTypeScore": 16.354,
"distanceErrorSum": 253,
"distanceAccuracySum": 111,
"distanceAccuracyScore": 3.0189560439560443,
"angleErrorSum": 4.476240332317074,
"angleAccuracySum": 5.297603478851171,
"angleAccuracyScore": 1.5122314200586873,
"totalScore": 112.75433094464756,
"shapedScore": 225.6584429542732
}