Shade distribution in Pacoima, California

We used Light Detection and Ranging (LiDAR) data to model urban form, mapping shade annual and diurnal cycle and estimate average cumulative solar exposure in Pacoima, Los Angeles County, California. 

Methods
We obtained LiDAR data from the LARIAC (Los Angeles Region Imagery Acquisition Consortium captured in early 2020. The LiDAR data has a point density between 2–3 points per square meter creating DEM, DSM and CHM with 1- meter resolution. We used Cloudcompare software and ArcGIS Pro 2.9 software to classify and process LiDAR data into Digital Surface Models and shadow raster for both trees and built form separately. Cloudcompare software was used to filter lidar points to vegetation (high, medium, and low) as one layer of lidar points, and filtered buildings as a second layer. Both layers were then used with Lastools toolbox on ArcGIS Pro to generate digital surface and canopy height models to then be used to model shadow using solar parameters of zenith and altitude. The output of the tools yielded a raster with extent of shade and unshaded spaces identified and the spatial resolution was the same as the digital surface models. This raster was reclassified to binary values of shade and solar exposed. For each hour we applied new solar zenith and altitude values into the calculation. The shade extent and composition varied and expanded throughout the afternoon as the sun's angle became more oblique. Vegetation shade was assumed to be complete shade with high leaf area index assumed. In cases where shade from buildings and tree shade overlapped, the higher elevated shade casting feature was given credit as source of shade.