acknowledgements for ansi/nist-itl 1-2011 - NIST Visual Image ...

ANSI/NIST-ITL 1-2011 - UPDATE 2013 DRAFT VERSIONrelative to the top left of Field 9.300: EFS region of interest / ROI. Note that thismeans that the X and Y values for CPR are the only EFS coordinates that may benegative, or greater than the ROI width or height. The center point of reference must bewithin the bounds of the overall image itself. Thus the allowed special character is thenegative sign.The location of a center point of reference can be determined using different algorithms,as stored in the Method information item, in which case different center points ofreference may be stored in different data entries (repeating subfield). The center point ofreference is defined for fingerprints or toe prints, not for other types of friction ridgeimages. This field consists of the following information items:• The first information item (method / CPM) is the method of determiningthe X, Y location, selected from the “Code” column of Table 41. It is a onecharacter value.• The second information item (‘x’ coordinate / PXC) is in units of 10micrometers (0.01mm)• The third information item (‘y’ coordinate / PYC) is in units of 10micrometers (0.01mm)• The fourth information item (radius of position uncertainty / CRU) isoptional. The radius of position uncertainty is 0 (default) if the location isknown precisely; otherwise the position is marked at the best estimate ofposition, with a radius including the area of other possible locations, ininteger units of 10 micrometers (0.01mm). The radius of uncertainty mayoverlap the edge of the image.Table 41 EFS methods of determining center point of reference locationsName Code DescriptionLateral center onlyLThe center location is defined laterally (across the finger) but is not meaningful inthe other dimension (longitudinally, or along the finger), such as for defining thecenter line of arches, tips, and lower joints. Lateral center is only meaningful if theorientation ( Field 9.301: EFS orientation / ORT) is known; the point marked isthe center with respect to the orientation angle.Uppermost point of the ridge withgreatest curvature0For a fingerprint with a known or estimated orientation, the center point isdetermined by finding the highest point of each ridge that is convex and pointingupward, and measuring the curvature/peak angle by following the ridge 1.63mm(0.064in) in both directions from that point. The point with the minimum angle(greatest curvature) is the center point of reference.Overall fingerprint focal point 1The overall fingerprint focal point is the point where the lines perpendicular toridge flow converge.May, 2013 DRAFT VERSION UPDATE 2013 Page 161