The two 3D models show the total daily solar irradiation simulated for a Summer day in Dublin. Total daily solar irradiation is the total amount of solar energy accumulated over the course of a day on a terrestrial surface. Dark brown represents shaded areas while bright yellow represents a high level of solar exposure. This simulation was performed for an area of 2 km2 of Dublin city in Ireland using a high-resolution, aerial LiDAR dataset collected by my research group at UCD. The two point clouds presented here are two small segments extracted from the large simulation. As the simulation involves a large amount of data (i.e. thousands of computations on billions of data points), a Big Data analytics solution was used. A paper reporting full details of the simulation is currently under review for publication.
Christ Church is an important medieval architecture in Dublin city center. This 3D model shows how amazing airborne LiDAR is in capturing the architectural details from 300m above the ground. Looking at the roof of the church, you will see the roof surface facing South receives to more sunlight than the one facing North. This is the typical pattern for any place in the Northern hemisphere.
This is the front entrance to the historic campus of Trinity College Dublin. Across the street is the Parliament House building, which used to be home to the Parliament of Ireland. The building now belongs to the Bank of Ireland. As the simulation takes full advantage of the geometrical details captured by LiDAR, the simulated solar potential result look highly detailed and realistic.
This model was generated by mapping the 3D laser points onto a 2D raster grid and computing an elevation value for each raster cell. The elevation value of a raster cell is the maximum elevation of the laser points mapped to the cell. The height values of empty raster cells (i.e. cells having no laser point) are interpolated from nearby cells. This model is 2.5D, meaning some 3D features in the original point cloud are lost during the mapping.
A voxel (i.e. volumetric pixel) is essentially a cube in a 3D space. A voxel model, composing of a set of voxels regularly distributed on a raster grid structure, is a 3D raster representation of the geometrical data. Voxel models are created from point clouds by mapping the 3D points onto a 3D raster grid. A voxel is added to the model wherever the corresponding raster cell contains a laser point. Unlike 2.5D DEMs, voxel models are truly 3D.