NIST Special Publication 800-76, Biometric Data Specification for Personal Identity Verification, contains specifications for acquiring, formatting, and storing fingerprint images and templates; for collecting and formatting facial images; and specifications for biometric devices used to collect and read fingerprint images.
The publication specifies that two fingerprints be stored on the card as “minutia templates”. These templates should be conformant to the INCITS 378-2004 minutiae template standard, and each finger’s template record shall be individually wrapped in the CBEFF structure, prior to storage on the card.
NIST originally wanted to store fingerprints as images on the cards, due to the fact that there were not deemed to be sufficient standards in place surrounding the use of minutae. But this decision was seen as flawed by industry as it might have entailed moving to smart cards with chips of greater capacity than 64K.
For a copy of NIST Special Publication 800-76 and more information on PIV click here