Bayfield Co. QL2 LiDAR (2015-16) - DEM

The Bayfield County lidar project area covers approximately 1681 square miles plus a 100 meter buffer around the county boundary. The lidar data was acquired at a nominal point spacing (NPS) of 0.7 meters and a single swath nominal point density (NPD) of 2.0. Project specifications are based on Bayfield County requirements and on the U.S. Geological Survey National Geospatial Program LiDAR Base Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83(2011) / WISCRS Bayfield (ftUS) (EPSG code: 7590), and vertical datum of NAVD88 - Geoid12A (Feet). LiDAR data was acquired in two phases using the Orion Optech H300 sensor; the first phase from October 22, 2015 to November 08, 2015, and the second phase on April 15, 2016. Acquisition occurred with leaves absent from deciduous trees, when no snow was present on the ground, and with rivers at or below normal levels.

The data was converted to vertical meters for ingest into the Digital Coast Data Access Viewer.

Original contact information:

Contact Name: Scott Galetka

Contact Org: Bayfield County

Title: Land Records Administrator

Phone: (715) 373-6156

Email: sgaletka@bayfieldcounty.org

This data, along with its derivatives, is the result of a countywide elevation mapping with cooperative partnerships from Bayfield County, Wisconsin DOA, and the USGS 3DEP program. This data was produced from lidar collected in October 2015, November 2015, and April 2016, which was processed and delivered in 2016.

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Any conclusions drawn from the analysis of this information are not the responsibility of Ayers Associates, the U.S. Geological Survey, the NOAA Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer

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No restrictions apply to these data.

None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these 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.

No formal attribute accuracy tests were conducted.

The project specifications require the vertical accuracy of the LiDAR data to be calculated and reported according to Non-vegetated Vertical Accuracy (NVA) and Vegetated Vertical Accuracy (VVA) classifications.

The required NVA for this project is 19.6 cm (0.643 survey feet) calculated at the 95 percent confidence level (AccuracyZ). The 95 percent confidence level statistic is derived according to National Standards for Spatial Data Accuracy (NSSDA) methodologies using RMSEz * 1.9600. This requirement is for the vertical accuracy testing of the raw swath lidar data and the derived digital elevation model (DEM). The AccuracyZ statistic is assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines. The minimum required number of NVA checkpoints for this project area is 86.

The required VVA for this project is 29.4 cm (0.965 survey feet) calculated 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 requirement is for the vertical accuracy testing of the derived digital elevation model (DEM). The minimum required number of VVA checkpoints for this project area is 64.

The NVA (bare earth and urban area land cover classes) and VVA (tall weeds, forested, and swamp land cover classes) checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. Elevations from the hydro flattened raster DEM were measured for the x,y location of each check point. Elevations interpolated from the hydro flattened raster DEM surface were then compared to the elevation values of the surveyed control points.; Quantitative Value: 0.109 meters, Test that produced the value: Tested 0.109 meters (0.358 survey feet) NVA at the 95 percent confidence level. The NVA of the DEM was calculated using 107 independent checkpoints located in the Bare Earth and Urban land cover categories.; Quantitative Value: 0.106 meters, Test that produced the value: Tested 0.106 meters (0.348 survey feet) NVA at the 95 percent confidence level. The NVA of the raw swath was calculated using 107 independent checkpoints located in the Bare Earth and Urban land cover categories.; Quantitative Value: 0.219 meters, Test that produced the value: Tested 0.219 meters (0.720 survey feet) VVA against the DEM at the 95th percentile. The VVA of the DEM was calculated using 64 independent checkpoints located in the tall weed, forested, and swamp land cover categories. The 95th percentile is determined by taking the absolute value of each elevation comparison between the VVA checkpoints and hydro flattened DEM, sorting the elevation values from lowest to highest, and discarding the highest 5% of the sorted elevation values. The next highest remaining value is the resultant 95th percentile value.

Spatial consistency of coverage of the Bayfield Co. QL2 LiDAR (2015-16) project area was maintained throughout the dataset.

Spatial consistency of coverage of the Bayfield Co. QL2 LiDAR (2015-16) project area was maintained throughout the dataset.