  On construction sites, progress must be monitored continuously to ensure that
the current state corresponds to the planned state in order to increase
efficiency, safety and detect construction defects at an early stage.
Autonomous mobile robots can document the state of construction with high data
quality and consistency. However, finding a path that fully covers the
construction site is a challenging task as it can be large, slowly changing
over time, and contain dynamic objects. Existing approaches are either
exploration approaches that require a long time to explore the entire building,
object scanning approaches that are not suitable for large and complex
buildings, or planning approaches that only consider 2D coverage. In this
paper, we present a novel approach for planning an efficient 3D path for
progress monitoring on large construction sites with multiple levels. By making
use of an existing 3D model we ensure that all surfaces of the building are
covered by the sensor payload such as a 360-degree camera or a lidar. This
enables the consistent and reliable monitoring of construction site progress
with an autonomous ground robot. We demonstrate the effectiveness of the
proposed planner on an artificial and a real building model, showing that much
shorter paths and better coverage are achieved than with a traditional
exploration planner.
