The limited vertical field of view of the Velodyne 16 and 32-line 3D lidars used with Stencil® work very well in outdoor and large indoor spaces. They do not do as well in tight quarters. The modeling technology in our products and online SaaS processing relies on laser scan matching to achieve its high level of accuracy but every modeling system has limitations. In particular, these approaches have difficulties handling extruded environments. In smaller rooms, tunnels, sewers, and hallways are constrained in two axes, but are unconstrained along the third axis (see diagram on the left side below the figure).

What this means is that smaller rooms, tunnels, stairwells, and narrow hallways have constraints in two axis, but are unconstrained along the third axis. This causes incorrect registration resulting in shortening, lengthening and twisting.

The small rooms look more like extruded sections, where they are constrained in two axis, but show a lot of drift along the third axis due to too little unique 3D structure for matching. As an example, see the figure to the left. This effect is seen whether the lidar is horizontal or tilted. When horizontal, the drift and twisting occurs along the z axis. When the lidar is tilted, the drift appears along the axis of movement. This may be x, y, or a combination of the two depending on the direction of movement relative to the pitch/tilt angle of the lidar.

Bottom line, this causes incorrect registration resulting in shortening, lengthening and twisting as can be seen in the figure to the left.

Kaarta Contour™ is better suited for these types of environments.