ANSI/NIST-ITL 1-2011 - NIST Visual Image Processing Group ...

ANSI/NIST-ITL 1-2011Data Format for the Interchange of Biometric and Forensic Informationregion of interest, even if the sampling points are at the edge of the region ofinterest.For each sampling point, angles shall be reported in integer degrees, with 0degrees to the right (horizontal), increasing counterclockwise to a maximumvalue of 179° (since 180°=0°). Undefined angles are recorded as noted in Error!Reference source not found..Note that the area used for determining direction (window size) may be larger orsmaller than the sampling frequency. Different window sizes may be used withina single image, at the discretion of the implementer. For example, animplementer may choose to use a uniform window size except in areas of highcurvature, in which a smaller window size may be used.13.7.17 EFS Field 9.311 Ridge Flow Map Format / RFFThis field permits setting the sampling frequency or data representation formatused in the Field 9.310 to values other than the defaults. Its use is conditional onthe presence of Field 9.310. This field consists of two information items:• The first information item (Sampling Frequency / SFQ) is set by defaultto 0.41mm (0.016"). This information item may be used to define higherresolution sampling frequencies than the default: valid settings range from“1” (0.01mm) through “41” (0.41mm).• The second information item (Data format / RDF) defines the format usedin the Ridge Flow Map field, as defined in Table 22. The default is theuncompressed (“UNC”) format79DRAFT 2