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<br />Distribution Format <br /> <br />The optional distribution format was designed to facilitate data usage. The <br />topological relationships explicitly encoded include starting node. ending node. <br />area to the left of direction of travel, and area to the right of the direction <br />of travel for line elements, bounding lines for area elements, and bounded lines <br />for node elements. These files can simplify proces sing requirements. For <br />example, because topological linkages are explicitly encoded for all line. node. <br />and area elements, a polygon data structure can be easily created. These <br />linkages facilitate Geographic Information System (GIS) applications of DLG data <br />as well as generation of graphic products. <br /> <br />The files are physically comprised of ASCII characters organized into fixed- <br />length logical records of 80 characters (bytes). Bytes 1- 7 2 of each record <br />contain DLG data, and bytes '3-80 may be blank or contain a re.oord sequence <br />number. <br /> <br />" <br /> <br />The record types used in the 0 tiona1 DLG distribution format may be categorized <br />as header and data records. <br /> <br />The actual sequence of records in an optional distribution format DLG file is as <br />follows: <br /> <br />1. Header records <br />Ten file identification and <br />description records <br />Control point identification records <br />(one per control point) <br />Data category identification records <br />(one per data category in the file) <br /> <br />2. <br /> <br />Data records <br />Node identification record <br />Node to-line linkage record(s) <br />Attribute Code record(s) <br /> <br />Repeated <br />for each <br />node "i chin a <br />daca c:acegory <br /> <br />Area identification record <br />Area-to-line linkage record(s) <br />Attribute code record(s) <br /> <br />Repea toed <br />for each <br />area "ithin a <br />daca c:acegory <br /> <br />Line identification record <br />Coordinate string record(s) <br />Attribute code record(s) <br /> <br />Repea l:ed <br />for e.:lch <br />line \lithin a <br />data category <br /> <br />Descriptions of the contents of the various t.ypes of records in an optional <br />format DLG follow. <br /> <br />10/93 <br /> <br />6 <br />