<p>Starting with 5G-NR standard and moving towards 6G, the mmW communications technology (in 6 − 300 GHz frequency range) fulfills the demand for high throughput in various parts of the radio access network. The fragile propagation characteristics of mmW signals compels a more meticulous radio network planning, even in the initial phases. Previously used in backhaul networks, the quality of mmW radio links significantly relies on the Line-of-Sight (LOS) signal paths between the communicating radios. LiDAR point cloud is a popular source of high-resolution aerial survey data suitable for accurate LOS assessments. In this work, we consider a comprehensive LOS assessment problem incorporating the radio mounting height, a key practical consideration in planning cellular networks. Then we proposed a method empowered by a novel topologically-sorted polar digital elevation model (DEM) and a new query-based algorithm to execute large-scale LOS assessments more efficiently and accurately than the stat-of-the-art methods. The post-deployment measurement reports indicate that using the proposed DEM leads to 50% reduction in the prediction errors compared to the other common methods. The proposed method is designed to process LOS assessment queries in constant-time, O(1), and achieves O(log N) speed-up over the known visibility algorithms when performing LOS assessments for the entire planning area (viewshed). The numerical results from our software implementation also confirm significant reduction in the viewshed computation time.</p>