Buildings for the urban/suburban areas of the County of Los Angeles developed from information captured in 2006 by the LAR-IAC program.
This dataset was developed by the County of Los Angeles Chief Information Office in support of the LA County Solar Map Application (http://solarmap.lacounty.gov). A solar model based upon the high-resolution digital aerial elevation data included the tops of trees, the ground, and other features that would skew any solar results. For example – the top of a tree appeared to the solar model to be a prime candidate for solar photovoltaic installation due to the amount of sunlight it received, but this was obviously incorrect, and some way needed to be found to focus exclusively on building tops for the purpose of the site.
The buildings were developed from the following three data sources:
- The Digital Elevation Model (DEM) which modeled the ground surface at 5-foot intervals. Click here for more information
- The Digital Surface Model (DSM) which modeled the surface at 5-foot intervals, which included all features like trees and buildings. Click here for more information
- The Color Infrared (CIR) imagery at 4-inch resolution which contains the Red and Near Infrared (NIR) Bands. Click here for more information
- A Surface Height Model was created by subtracting the DEM from the DSM: Click here for more information
- A Normalized Difference Vegetation Index (NDVI) model was created. Click here for more information. NDVI values range between -1 and 1. Values > 0.1 are generally green vegetation, while values < 0.1 show things like buildings, streets, water and bare dirt.
- All areas where the surface height was greater than 8 feet, and the NDVI value was < 0.1 were extracted and assigned the value 1. This is the building layer.
This building layer has been validated to provide a true representation of buildings. However, the data includes many small processing artifacts, and should not be used for authoritative measuring, roof areas, etc.