2018 - 2019 USGS Lidar DEM: Lower Colorado River (AZ, CA, NV)

Original Product: 0.5-meter bare-earth raster digital elevation model (DEM) data tiles in ERDAS IMG format.

Original Full Dataset Geographic Extent: Approximately 2,122 square miles of the Lower Colorado River in Arizona, Nevada and California. Portions of the AOI in Arizona and California are along the U.S. and Mexico border.

Original Dataset Description: The AZ Lower Colorado River 2018 B18 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 0.35 meters. Project specifications were based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. DEM data was delivered as processed ERDAS IMG files formatted to individual 1,000-meter x 1,000-meter tiles.

Ground Conditions: Lidar was collected from September 2, 2018 through September 29, 2019 in 27 missions by Woolpert while no snow was on the ground and rivers were at or below normal levels. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established 131 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 155 independent accuracy checkpoints (86 NVA points and 69 VVA points), were collected 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.

The Boulder Canyon Operations Office (BCOO) and the Lower Colorado River Multi-Species Conservation Program (LCR MSCP) of the Lower Colorado Region of the US Bureau of Reclamation both have a need for updated vegetation mapping products along the lower Colorado River. BCOO uses vegetation mapping projects for calculating evapotranspiration estimates of agricultural and riparian vegetation along the lower Colorado River. The LCR MSCP uses vegetation mapping projects for several purposes including identification of survey areas for various wildlife monitoring projects, identification of potential areas for the habitat maintenance fund, and analysis of habitat use of LCR MSCP covered species. In addition to the vegetation mapping project that the lidar will be used for, the LCR MSCP has a need for high-resolution / high-accuracy topographic products for construction planning for the creation of habitat restoration sites. Other offices within the region also have a need for the same products for construction and operations/maintenance activities.

USGS Contract No. G16PC00022; Task Order No. 140G0218F0411. Contractor: Woolpert. Raster File Type = IMG Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 0.5 Meter Interpolation or Resampling 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.

To the extent possible under law, the U.S. Government has waived all copyright and related or neighboring rights to this dataset.

Data is available online for bulk and 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.

Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data. 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.

Microsoft Windows 10; Esri ArcCatalog v10.4; Esri ArcMap 10.4; IPAS Pro v.1.35; LP360 v2018.1.57.4; Leica CloudPro 1.2.4; Novatel Inertial Explorer v8.60.6129; POSPac Software v. 5.3; TerraMatch v18; TerraModeler v18; TerraScan v18

This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 13.3 cm RMSEx / RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 32.7 cm at a 95% confidence level.

This project required Non-Vegetated Accuracy (NVA) and Vegetated Vertical Accuracy (VVA) testing of the digital elevation model (DEM) dataset. The calculated NVA value was required to meet 19.6 cm at a 95% confidence level using an RMSEz target value of 10 cm x 1.9600. VVA was required to meet 0.30 cm at the 95th percentile error. Testing was assessed and reported using guidelines developed by the National Digital Elevation Program (NDEP) and the American Society for Photogrammetry and Remote Sensing (ASPRS).

Testing was performed using the bare earth DEM created as part of this task order. For each checkpoint, an elevation value was derived from the DEM at the point's x,y location. This value was compared to the checkpoint's surveyed elevation value. The NVA was to be calculated with a minimum of 73 independent checkpoints falling on bare earth and urban (non-vegetated) classes. VVA had a minimum requirement of 57 independent checkpoints falling in brush/tall grass/weeds (vegetated) land cover classes. These points were not used in the calibration or post processing of the lidar point cloud data and distributed throughout the project area. Checkpoints were surveyed using GPS techniques. See the survey report for acquisition methodologies.

The DEM NVA measured 0.131 meters using an RMSEz of 0.067 meters x 1.9600 using 86 checkpoints. VVA tested 0.275 meters at the 95th percentile using 69 checkpoints.

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 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.