New York Office of Information Technology Services 20251210 raster digital data Product: These are Digital Elevation Model (DEM) data as part of the required deliverables for the lidar project. Class 2 (Ground) lidar points in conjunction with the hydro breaklines were used to create a 1 meter hydro-flattened Raster DEM. Geographic Extent: Long Island, New York, covering approximately 1,627 square miles. Dataset Description: The 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 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification v2024, Rev. A. The data was developed based on a horizontal projection/datum of NAD83 (2011), Universal Transverse Mercator Zone 18N, meters and vertical datum of NAVD88 (GEOID18), meters. Lidar data was delivered as flightline-extent unclassified LAS swaths, and as processed Classified LAS 1.4 files, formatted to 1,873 individual 1500 m x 1500 m tiles, as tiled bare-earth DEMs; all tiled to the same 1500 m x 1500 m schema. Ground Conditions: Lidar was collected in early 2024, 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, Sanborn Map Company, Inc., established a total of 31 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 102 independent accuracy checkpoints, 72 in Bare Earth and Urban landcovers (72 NVA points), 30 in Tall Grass and Brushland/Low Trees categories (30 VVA points), were used to assess the vertical accuracy of the data. These check points were not used to calibrate or post process the data. 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 lidar point cloud data were used to create intensity images, 3D breaklines, and hydro-flattened DEMs as necessary. Raster File Type = TIFF Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 1 Meter Interpolation or Resampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA 20240324 20240416 ground condition Complete None planned -73.78329791 -71.83437964 41.34691317 40.52740079 603000 765000 4578000 4491000 None Model Raster DEM Remote Sensing Elevation Data Lidar None New York Nassau County Queens County Suffolk County 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 the limitations of the data. Acknowledgement of New York Office of Information Technology Services would be appreciated for products derived from these data. The data represented is the result of data collection and processing per contract specifications and indicates the general existing conditions at the time of the data collection. As such, it is only valid for its intended use, content, time, and accuracy specifications. The user is responsible for the results of any application of the data for other than its intended purpose. Data covers the DPA specified for this project. 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. This data set was tested to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10cm RMSEz Vertical Accuracy Class. Actual NVA accuracy was found to be RMSEz = 6.6cm, equating to +/- 13.0cm at 95% confidence level. Actual VVA accuracy was found to be +/- __cm at the 95th percentile. Hydro-Flattened Bare-Earth DEM Process: Class 2 (Ground) lidar points in conjunction with the hydro breaklines were used to create a 1 meter hydro-flattened Raster DEM. Using automated scripting routines within LP360, a GeoTIFF file was created for each tile. Each surface is reviewed using Global Mapper to check for any surface anomalies or incorrect elevations found within the surface. 2025 Raster Pixel 1500 1500 Universal Transverse Mercator 18 0.9996 -75.0 0.0 500000 0.0 coordinate pair 0.001 0.001 meters North American Datum of 1983 (2011) Geodetic Reference System 80 6378137 298.257222101 North American Vertical Datum of 1988, Geoid 18 0.001 meters Explicit elevation coordinate included with horizontal coordinates 20251210 20251210 New York Office of Information Technology Services mailing and physical

W. Averell Harriman State Office Campus

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Albany NY 12226 USA (518) 242-5037 FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 None. None. None. Unclassified. None. None. None.