Tree Canopy 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 updated in October 2011 – see below for details.
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.
Samples
 Countywide |
 Detail View (click to enlarge) |
 Detail View with Imagery |
The trees 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
Processing steps:
- 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 trees layer.
- The MajorityFilter command was run twice on the trees layer. For the options, I used 8 neighbors with the majority replacement threshold.
- I created a copy of the result, then shifted it three feet to the east and south to establish a “shadow” effect, and assigned the shadow the value of 100. This will allow symbolization or removal of the shadow.
- I merged the two rasters back together to create a single raster dataset with both the tree and shadow data in the same raster.
 Original |
 Updated |
Important notes
This trees layer has been validated to provide a true representation of trees. However, the data includes many small processing artifacts, and should not be used for authoritative measuring.
Layer Files
Tree Canopy (2006) – Updated (ArcGIS 10 Layer File) – This will work only for users connected to the LA County Network.
This data is part of the LAR-IAC (http://planning.lacounty.gov/lariac) datasets, and if you want use access this information you will need to participate in LAR-IAC.
Since this is derived from a licensed dataset we aren’t able to provide to the public, but it has been included in some of the ESRI basemaps, as well as our own on our GIS Viewer (http://gis.lacounty.gov/gisviewer).
We had to get our vendors to agree to releasing the building outlines – I’ll follow up with the source of the Tree Canopy and see if they would be willing to do the same.
Are there any plans to make this data set publicly available, similar to the building outlines layer? It would be quite useful for analyses of street-level green space in the city as well as a nice addition to large-scale basemaps.
Thanks!
[…] More information about this dataset can be found here: http://egis3.lacounty.gov/dataportal/?p=1053 […]