2024 USGS Lidar DEM: Houston, TX

Product: These are Digital Elevation Model (DEM) data for Texas as part of the required deliverables for the TX_Houston_B24 project. Class 2 (ground) LiDAR points in conjunction with the hydro breaklines were used to create a 0.5 hydro-flattened Raster DEM.

Geographic Extent:

TX_Houston_1 (Work Unit 300808) - parts of 10 counties (Grimes, Hardin, Harris, Jefferson, Liberty, Montgomery, Polk, San Jacinto, Walker, Waller), covering approximately 3734 total square miles

TX_Houston_2 (Work Unit 300805) - parts of 6 counties (Brazoria, Fort Bend, Harris, Matagorda, Waller, Wharton), covering approximately 2758 total square miles

TX_Houston_3 (Work Unit 300806) - parts of 7 counties (Brazoria, Chambers, Fort Bend, Galveston, Harris, Jefferson, Liberty) , covering approximately 3260 total square miles

TX_Houston_4 (Work Unit 300807) - parts of 9 counties (Austin, Colorado, Fayette, Fort Bend, Grimes, Matagorda, Waller, Washington, Wharton), covering approximately 1812 total square miles

Dataset Description: The TX_Houston_B24 project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, 2024 Rev. A.

Ground Conditions: LiDAR was collected in winter and spring 2024, while no snow was on the ground and rivers were at or below normal levels.

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.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create intensity images, breaklines and raster DEMs. The purpose of these LiDAR data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 0.5 cell size. These raw LiDAR point cloud data were used to create classified LiDAR LAS files, intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

Raster File Type = GeoTIFF; Bit Depth/Pixel Type = 32-bit float; Raster Cell Size = 0.5; Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary; Required Vertical Accuracy = 0.196

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

TX_Houston_1 (Work Unit 300808) - parts of 10 counties (Grimes, Hardin, Harris, Jefferson, Liberty, Montgomery, Polk, San Jacinto, Walker, Waller), covering approximately 3734 total square miles

TX_Houston_2 (Work Unit 300805) - parts of 6 counties (Brazoria, Fort Bend, Harris, Matagorda, Waller, Wharton), covering approximately 2758 total square miles

TX_Houston_3 (Work Unit 300806) - parts of 7 counties (Brazoria, Chambers, Fort Bend, Galveston, Harris, Jefferson, Liberty) , covering approximately 3260 total square miles

TX_Houston_4 (Work Unit 300807) - parts of 9 counties (Austin, Colorado, Fayette, Fort Bend, Grimes, Matagorda, Waller, Washington, Wharton), covering approximately 1812 total square miles

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.

Lidar horizontal accuracy is a function of Global Navigation Satellite System (GNSS) derived positional error, flying altitude, and INS derived attitude error. The obtained RMSEr value is multiplied by a conversion factor of 1.7308 to yield the horizontal component of the National Standards for Spatial Data Accuracy (NSSDA) reporting standard where a theoretical point will fall within the obtained radius 95% of the time. Based on a flying altitude of 1,950 meters, an IMU error of 0.003 decimal degrees, and a GNSS positional error of 0.027 meters, this project was compiled to meet 0.32 meter horizontal accuracy at the 95% confidence level.

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

USGS Determined DEM Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 3.34 cm RMSE

Vegetated Vertical Accuracy (VVA) = 21.65 cm at 95th Percentile

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 raw point cloud is of good quality and data pass Non-Vegetated Vertical Accuracy specifications.

Data cover the entire area specified for this project.

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.