  Place recognition is a key module in robotic navigation. The existing line of
studies mostly focuses on visual place recognition to recognize previously
visited places solely based on their appearance. In this paper, we address
structural place recognition by recognizing a place based on structural
appearance, namely from range sensors. Extending our previous work on a
rotation invariant spatial descriptor, the proposed descriptor completes a
generic descriptor robust to both rotation (heading) and translation when
roll-pitch motions are not severe. We introduce two sub-descriptors and enable
topological place retrieval followed by the 1-DOF semi-metric localization
thereby bridging the gap between topological place retrieval and metric
localization. The proposed method has been evaluated thoroughly in terms of
environmental complexity and scale. The source code is available and can easily
be integrated into existing LiDAR simultaneous localization and mapping (SLAM).
