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Solar Radiation Model (2006)

Solar Insolation (global radiation) for the County of Los Angeles developed from information captured in 2006 by the LAR-IAC program.

This data was created through the Area Solar Radiation function in ESRI’s ArcGIS Desktop.  For more details about this function, view the ESRI help file.  That function creates four output files:

  • Global radiation – Global radiation or total amount of incoming solar insolation (direct + diffuse) calculated for each location of the input surface.
  • Direct radiation – Direct incoming solar radiation for each location.
  • Diffuse radiat ion – Diffuse incoming solar radiation for each location.
  • Duration – Duration of direct incoming solar radiation

This dataset is the first output – global radiation.Values are watt-hours per square meter per year, and range from zero to over 2.6 million.  Further analysis has determined that these values may be 28% low when compared to real-world test locations, at LAX and Long Beach Airport (Federal Solar Fact Sheets.)    It is recommended that the values be scaled up by this percent to build accurate models.

There are two versions of this file.  The first is the raster dataset, samples of which are shown below.  The second version is a point file version, which converted each 5′ x 5′ grid into a single cell that could be assigned to a specific building and parcel, and aggregated for use in the LA county Solar Map.  This point file is massive, and should not be viewed except at extremely large scales.





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).  It is a 5 foot by 5 foot raster grid that coveres all areas of the County that had the necessary data.  This is the raw source data that includes  includes the tops of trees, the ground, buildings, water, and all features.  This means that features like the top of a tree will appear to be  be a prime candidate for solar photovoltaic installation due to the amount of sunlight it received.

This dataset is perhaps the largest single solar radiation model in the world, consisting of over 300 million individual measurements.

For the solar map site itself, further processes were run to focus only on building roofs.  This dataset includes ALL information, and can be used for determining solar potential for ground-based systems as well.

Data shown on the  Solar Map included a number of other processing steps, which created a raster building dataset, which was used to mask this solar data to focus only on buildings.

Detailed Graphic view of processing steps (4.6 Mb .pdf file)

Important notes

This layer has been validated by various researches, and its values are accurate to within 4% when aggregated to the parcel level.


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Data Field Descriptions
This dataset has a single pixel value, which is the Global radiation or total amount of incoming solar insolation (direct + diffuse) calculated for each location of the input surface.  Units are watt-hours per square meter.
Since the raster grid is 5 feet by 5 feet (25 square feet), and the values are per square meter, to determine actual insolation for a specific cell, you must convert from square feet to square meters.
1 meter = 3.281 square feet.
1 square meter = 10.764961 square feet.
25 square feet divided by 10.764961 = 2.32235 square meters for each cell.
Actual insolation values for an individual cell must be multiplied by 2.32235 to determine total insolation for that cell.

GIS Source Information
Database Name: AERIAL
Feature Class Name: LARIAC_SOLAR_POINTS_25F
Feature Dataset Name (if applicable): SOLAR
Reference Date: 2006
Accuracy: Parcel
Update Frequency: Unknown
Access Constraints:Government

Contact Information
Steve Steinberg
Geographic Information Officer
County of Los Angeles
Internal Services Department
9150 E. Imperial Hwy, MS#3
33.916650, -118.132255
Downey, CA 90242
(562) 392-7126

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