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B4 Project - Southern San Andreas and San Jacinto Faults

Dataset Overview:

This page offers access to LiDAR point cloud data of the southern San Andreas and San Jacinto Faults acquired by the National Center for Airborne Laser Mapping (NCALM) through funding from the National Science Foundation (NSF) as part of the "B4 Project". The B4 Project has kindly agreed to make these data available to the research community through the GEON OpenTopography Portal. If you utilize the B4 data for talks, posters or publications, we ask that you acknowledge the B4 project. The B4 logo can be downloaded here.  NCALM Logo

Interactive Spatial Selection of LiDAR Topography

Navigation of the Google Map above is performed using the zoom bar and navigation arrows in the upper left hand corner of the map. To select data, use the box selection tool just below the zoom bar. Use the tool to draw a box on the map that corresponds to the portion of the LiDAR dataset that you are interested in processing and downloading. The bounds of the LiDAR dataset are shown as an orange polygon that overlays the Google Map.

Data selection coordinates

Coordinates are in UTM Zone 11 N WGS84 Meters:
MinX   MinY  
MaxX   MaxY  

Point Cloud Data Download
Selection of this option returns the LiDAR point cloud for the area selected above as a compressed ASCII file (comma delimited, one point per line). If you only wish to download the raw data it is not necessary to select any of the options in the "Processing Algorithms and Derived Products" section below. Download raw data (Query result in compressed ASCII File)

DEM Generation via Local Binning Algorithms

 This local binning algorithm utilizes the elevation information from LiDAR returns contained within a circular search area (radius defined by the user) to calculate the DEM elevation at each grid cell (resolution specified by the user). Five values are computed for each node in a grid: 1) the minimum, 2) maximum, 3) mean, and 4) inverse distance weighted mean of the local points, and 5) the number of points in the search area. If the number of points in the search radius is 0, the grid node is assigned a null value. This code offers substantially better performance than the GRASS spline interpolation algorithm also offered by the GLW (see below). The local binning algorithm was written by Han Suk Kim (UCSD).For more information on this algorithm please refer to the documents section under the resources tab. Note that the defaults are that the search radius is grid resolution * sqrt(2)/2 which gives optimal coverage for each grid cell (but the area of the search radius is 1.57x larger than the grid cell area).
  Interpolation Method Product Download Format    The data products created by the GEON LiDAR workflow may be download in the following formats:

Arc Grid: This ascii grid format is designed for import into ESRI software such as ArcGIS. The Arc Grid can be imported through ArcToolbox by selecting - Conversion Tools > To Raster > ASCII to Raster. "Output data type" should be set to "float".

ascii grid: A standard ascii grid format that should be importable to software packages that can handle ascii grids (e.g. GMT).
DEM grid cells are assigned the minimum elevation value of points within the user defined search radius. In unfiltered LiDAR point clouds this option may be useful for removing much of the vegetation. Min Arc Grid Ascii Grid
DEM grid cells are assigned the maximum elevation value of points within the user defined search radius. In unfiltered LiDAR point clouds this option generates a first return surface. Max Arc Grid Ascii Grid
DEM grid cells are assigned the mean elevation value of points within the user defined search radius. Mean Arc Grid Ascii Grid
DEM grid cells are assigned the inverse distance weighted mean elevation value of points within the user defined search radius. IDW Arc Grid Ascii Grid
Grid cell is populated with the number of points within the user defined search radius. This product can be exceptionally useful for evaluating LiDAR return concentration and allows users to better understand what resolution DEM the dataset will support. Point Count Arc Grid Ascii Grid

Algorithm Parameters
Sets the resolution of the Digital Elevation Model (DEM) generated by the interpolation. Grid resolution is set in the same units as the data set. Grid Resolution (Default=1 meter)   
Sets the radius of the search area used to perform the calculations above. If no value is entered, the default is used. Please refer to the documents section under the resources tab for further information. Enter radius value
(Default= 1 meter or √2)/2 * Resolution, whichever is greater)		   

DEM Generation via Spline Interpolation Algorithm

 Interpolation of the LiDAR data and calculation of derived products is performed via GRASS Open Source GIS. GRASS is running on the SDSC LiDAR Compute Cluster and is accessed in this workflow via web service architecture. Currently, spline interpolation jobs are limited to 1.6 million points.

Job Description

These options allow users to describe and keep track of their jobs. Information entered below is recorded along with other job parameters in your personal LiDAR Job archive accessed via myOpenTopo (available only to registered OpenTopography users).

Job title   
Job description (up to 500 characters):

Email Address
Enter your e-mail address for notification upon completion of processing