2016 NOAA Topobathy Lidar DEM: Upper Lake Michigan Islands

This digital elevation model (DEM) was created from data collected by Leading Edge Geomatics using a Leica Chiroptera II Bathymetric & Topographic Sensor. The project consists of approximately 205 square miles of data along the shores of the Beaver Island Archipelago and South Manitou Islands in Upper Lake Michigan. The data were acquired between November 16, 2015 through December 5, 2015 for Beaver Island, North Fox Island, Gull Island, High Island, Garden Island, and Isle Aux Galets. The data for South Manitou Island, South Fox Island and several smaller islands that needed to be re-acquired on Beaver Island due to data gaps, were acquired on June 2, 2016 and June 3, 2016. The data includes topobathy data classified as: created, never classified (0), unclassified (1), ground (2), submerged topography (40), water surface (41), derived water surface (42), no bottom found (45) in accordance with project specifications. Data that was classed as ground (2) and submerged topography (40), were used to create the 2 meter DEMs. This dataset contains 3,361 500 m x 500 m lidar tiles. In addition to the DEM data, the classified lidar point data that these DEMs were created from are also available. The data are available from the NOAA Digital Coast at: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=5182

Original contact information:

Contact Org: NOAA Office for Coastal Management (OCM)

Phone: 843-740-1202

The Beaver Islands Archipelago and South Manitou Islands have been identified as having critical topographic and bathymetric data gaps by NOAA. This lidar data will fill those critical gaps.

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Data include all lidar returns. An automated grounding classification algorithm was used to determine bare earth and submerged topography point classification. The automated grounding was followed with manual editing. Classes 2 (ground) and 40 (submerged topography) were used to create the final DEMs. The full workflow used for this project is found in the final project report submitted to NOAA. The final report for this data set may be viewed at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid12b/5182/supplemental/mi2016_noaa_topobathy_upper_lake_mi_islands_m5182_lidarreport.pdf

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the National Geodetic Survey, the Office for Coastal Management, or its partners. This data can be obtained online at the following URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=6195

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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.

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Project specifications require horizontal positions to meet 1.0m RMSE.; Quantitative Value: 1 meters, Test that produced the value: Independent horizontal accuracy testing requires photo-identifiable survey checkpoints, which is not always possible with elevation data. No photo-identifiable areas could be found in the lidar intensity imagery and horizontal accuracy could not be computed for the lidar data. The lidar data is compiled to meet the 1.0 m RMSE horizontal accuracy specification through rigorous processing of airborne GPS and IMU, use of control, and calibration procedures.

The DEMs are derived from the source lidar and inherit the accuracy of the source data. The DEMs are created using controlled and tested methods to limit the amount of error introduced during DEM production.

The DEMs are derived from the source lidar and inherit the accuracy of the source data. The DEMs are created using controlled and tested methods to limit the amount of error introduced during DEM production so that any differences identified between the source lidar and final DEMs can be attributed to interpolation differences. DEMs are created by averaging several lidar points within each pixel which may result in slightly different elevation values at a given location when compared to the source LAS, which does not average several lidar points together but may interpolate (linearly) between two or three points to derive an elevation value.

The vertical accuracy of the DEMs was verified by Dewberry with 21 non-vegetated survey checkpoints and 12 vegetated survey checkpoints.

The vertical accuracy is tested by comparing control points to the final topobathymetric DEM surface and extracting the elevation of the DEM pixel that contains the xy location of each control point.

Non-vegetated survey checkpoints will be used to compute the Non-Vegetated Vertical Accuracy (NVA). Project specifications require a NVA of 19.6 cm at the 95% confidence level based on RMSEz (10 cm) x 1.9600.

All vegetated survey checkpoints will be used to compute the Vegetated Vertical Accuracy (VVA). Project specifications require a VVA of 29.4 cm based on the 95th percentile.; Quantitative Value: 0.156 meters, Test that produced the value: This DEM dataset was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 10 cm RMSEz Vertical Accuracy Class. Actual NVA accuracy was found to be RMSEz = 8.00 cm, equating to +/- 15.6 cm at 95% confidence level.; Quantitative Value: 0.244 meters, Test that produced the value: This DEM dataset was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 10 cm RMSEz Vertical Accuracy Class. Actual VVA accuracy was found to be +/- 24.4 cm at the 95th percentile.

The 5% outliers consisted of 1 checkpoint that is larger than the 95th percentile. This checkpoint has a DZ value of 0.268 m.

Data covers the 3,361 tiles (500m x 500m tiles).

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