Lines are checked to assure that all intersections have nodes present. Validation of DLG data is performed for each category within a file. Edge matching is conducted interactively at the time of original compilation and some revisions using source materials for verification. Edge align software automatically compares position and attribution, and aligns features that are within 0.020 inches of each other. The unit sizes in Alaska vary depending on latitude.
Nodes define the location of the endpoints of every line.
A line is an ordered set of points that describes the position and shape of a linear feature on a map. Lines may not cross over themselves or any other lines except at a node. An area is a continuous unbroken region of a map bounded by lines. Additional areas are identified as necessary to subdivide the area covered by the file. Polygons as unique features are not defined explicitly in a DLG file.