2018 FEMA Lidar DEM: Region 9, CA

Product: 3-foot bare-earth raster digital elevation model (DEM) data tiles in 32-bit floating point ERDAS IMG format.

Geographic Extent: Approximately 10,547 square miles across 6 AOIs in California.

Dataset Description: The CA-AZ FEMA R9 Lidar lidar project called for the planning, acquisition, processing, and production of derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meters. Project specifications were based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2. The data was developed based on a horizontal datum/projection of NAD83 (2011) State Plane California I & IV (FIPS Zone 0401 & 0404), US Survey Feet, and a vertical datum of NAVD88 (GEOID12B), US Survey Feet. Lidar data was delivered as processed LAS 1.4 files formatted to 10,516 individual 4,500-feet x 4,500-feet tiles.

Ground Conditions: Lidar was collected in 2018 while no snow was on the ground and rivers were at or below normal levels. Due to a time difference of approximately one month between adjacent flight lines, there are two instances, a reservoir and a river bed, that show elevation drop-offs. Initial acquisition occurred when these features were dry, with the features containing water at the time of the follow-up flights. The feature portions that contain water were digitized, hydro-flattened, and incorporated into the DEM. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established 148 ground control points across all California AOIs that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 258 independent accuracy checkpoints (145 NVA points and 113 VVA points), were collected across all California AOIs and used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

High quality elevation data products are critical for riverine floodplain study and mapping for the National Flood Insurance Program. This acquisition allows FEMA Region IX to produce floodplain analysis where it is needed, to provide updates to flood insurance rate maps, and to produce floodplain administration decision support tools.

FEMA, in administration of the National Flood Insurance Program and under FEMAs Risk Mapping Assessment and Planning (Risk MAP) program, orders these elevation products to meet or exceed the quality specifications published by the US Geological Survey for acceptance into the 3-D Elevation Program (3-DEP). Data of this quality is interpreted as sufficient for floodplain engineering studies, analysis, and mapping of flood hazard.

USGS Contract No. G16PC00022 Task Order No. 140G0218F0027. CONTRACTOR: Woolpert. Sub-Contractors: Aerial Services, Inc. (ASI), Aero-Graphics, Keystone Aerial Surveys. Raster File Type = IMG Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 3 Foot Interpolation or Re-sampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk or custom downloads

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and within the limitations of the data for which it was requested and prepared, in general, and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data. It is not appropriate to use the related graphics as data. Woolpert gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from a Woolpert server, and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully upon Woolpert's computer system, no warranty, expressed or implied, is made regarding the utility of the data on another system, or for general or scientific purposes; nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data.

Microsoft Windows 10; Esri ArcCatalog v10.4; Esri ArcMap v10.4; GeoCue 2017.1.14.1; IPAS Pro v1.35; LP360 v2018.1.57.4; Leica CloudPro v1.2.4; Novatel Inertial Explorer v8.60.6129; POSPac Software v5.3; TerraMatch v18; TerraModeler v18; TerraScan v18.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

The following Vertical Accuracy information is from the USGS analysis for the DEM product.

The number of Checkpoints tested for NVA : 237

The NVA RMSEz= 5.38 cm

The NVA Accuracy z at 95% confidence interval (RMSEz * 1.96) = 10.54 cm

The number of checkpoints tested for VVA : 164

The 95th percentile value for VVA is : 21.29 cm

Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The DEM is of good quality and data passes Non-Vegetated and Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.

Data is backed up to tape and to cloud storage.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.