A handheld device with a graphical user interface (GUI) for entering and displaying blueprint data as a hierarchical sequence of segments. A handheld device having a touchscreen and/or keys is used to sequentially enter line segments and arcs to enter blueprint data into the device. Each line segment or arc that is entered may be referenced to an existing endpoint or start point of a previously entered line segment or arc. A blueprint entered into the handheld device may be edited by modifying, deleting, or inserting a line segment or arc. When an edit is performed, the line segments and arcs in the sequence that follow the element being edited may be automatically modified to maintain continuity in the blueprint without disturbing prior segments in the sequence.