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          CHAPTER 8                                                               Interactive Features




                              TABLE 8.110 Entries in a measure dictionary
KEY         TYPE          VALUE

Type        name          (Optional) The type of PDF object that this dictionary describes; must be Measure
                          for a measure dictionary.

Subtype     name          (Optional) A name specifying the type of coordinate system to use for measuring.
                          Default value: RL, which specifies a rectilinear coordinate system

          Table 8.111 shows the additional entries in a rectilinear measure dictionary. Many
          of the entries in this dictionary are number format arrays, which are arrays of
          number format dictionaries (see Table 8.112). Each number format dictionary
          represents a specific unit of measurement (such as miles or feet). It contains in-
          formation about how each unit is expressed in text and factors for calculating the
          number of units.

          Number format arrays specify all the units that are to be used when expressing a
          specific measurement. Each array contains one or more number format dictio-
          naries, in descending order of granularity. (For example, a number format dictio-
          nary specifying feet should precede one specifying inches.) All the elements in
          the array contain text strings that, concatenated together, specify how the units
          should be displayed. For example, a measurement of 1.4505 miles might be ex-
          pressed as “1.4505 mi”, which would require one number format dictionary for
          miles, or as “1 mi 2,378 ft 7 5/8 in”, which would require three dictionaries (for
          miles, feet, and inches).

                    TABLE 8.111 Additional entries in a rectilinear measure dictionary
KEY         TYPE          VALUE

R           text string   (Required) A text string expressing the scale ratio of the drawing in the region corre-
                          sponding to this dictionary. Universally recognized unit abbreviations should be
                          used, either matching those of the number format arrays in this dictionary or those
                          of commonly used scale ratios. For example, a common scale in architectural draw-
                          ings is “1/4 in = 1 ft”, indicating that 1/4 inches in default user space is equivalent to
                          1 foot in real-world measurements.
                          If the scale ratio differs in the x and y directions, both scales should be specified; for
                          example, “in X 1 cm = 1 m, in Y 1 cm = 30 m”.

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