2018 USGS Lidar DEM: Florida Panhandle

Product: These are Digital Elevation Model (DEM) data for FL Panhandle as part of the required deliverables for the 2018 FL Panhandle Lidar project. Class 2 (ground) lidar points in conjunction with the hydro breaklines were used to create a 1 meter hydro-flattened Raster DEM. This delivery consists of 2859 tiles.

Geographic Extent: Bay, Calhoun, Covington, Decatur, Dixie, Escambia, Franklin, Gadsden, Geneva, Grady, Gulf, Holmes, Houston, Jackson, Jefferson, Lafayette, Leon, Liberty, Madison, Okaloosa, Santa Rosa, Seminole, Taylor, Thomas, Walton, Wakulla, Walton, and Washington counties, Florida, covering approximately 5,952 square miles.

Dataset Description: FL Panhandle 2018 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on a horizontal projection/datum of NAD83 (2011), Albers Equal Area, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 16,768 individual 1000 m x 1000 m tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 1000 m x 1000 m schema.

Ground Conditions: Lidar was collected in early 2018, 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, Airborne Imaging used 30 control points (16 FL DOT FPRN stations, 5 NGS monuments, and 9 newly established base stations) to control the lidar acquistion and tie the lidar to known ground locations established throughout the FL Panhandle project area. Over 15,000 GNSS kinematic points were used by Airborne Imaging to verify accuracy of the calibarted lidar data. An additional full AOI will be tested with 262 independent accuracy checkpoints, 152 in Bare Earth and Urban landcovers (152 NVA points), 110 in Tall Grass and Brushland/Low Trees categories (110 VVA points), but interim accuracy of Block 1 was tested with 22 in Bare Earth and Urban landcovers (22 NVA points), 12 in Tall Grass and Brushland/Low Trees categories (12 VVA points), were used to assess the vertical accuracy of the Block 1 data. These checkpoints were not used to calibrate or post process the data.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from, are also available. These data and the breaklines are available for download at the links provided in the URL section of this metadata record.

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 DEM. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 1 meter cell size. These raw lidar point cloud data were used to create classified lidar LAS files, intensity images, 3D breaklines, hydro-flattened DEMs as necessary.

Raster File Type = IMG

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 1.0 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 Dewberry, the USGS, NOAA, the Office for Coastal Management or its partners.

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.

The project specifications require the accuracy (ACCz) of the derived DEM be calculated and reported in two ways:

1. The required NVA is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the “bare earth” and "urban" land cover classes. This is a required accuracy. The NVA was tested with 127 checkpoints located in bare earth and urban (non-vegetated) areas.

2. Vegetated Vertical Accuracy (VVA): VVA shall be reported for "brushlands/low trees" and "tall weeds/crops" land cover classes. The target VVA is: 30cm at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data, i.e., based on the 95th percentile error in all vegetated land cover classes combined. This is a target accuracy.

Tested 0.132 meters NVA at a 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). RMSEz is 6.7 cm. The NVA of the DEM was calculated using 127 independent checkpoints located in the Bare Earth and Urban land cover categories.

Tested 0.145 meters VVA was calculated using 89 checkpoints located in the Brushlands and Low Trees and Tall Weeds and Crops land cover categories at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data. Tested against the DEM.

The VVA was tested with 89 checkpoints located in tall weeds/crops and brushlands/low trees (vegetated) areas. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. AccuracyZ has been tested to meet 19.6 cm or better Non-Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

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 passes Non-Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.