2018 FEMA Lidar DEM: Franklin, Fulton, Herkimer, Montgomery, and Saratoga Counties, NY

Product: These are Digital Elevation Model (DEM) data for Upstate New York as part of the required deliverables for the New York FEMA 2018 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: Five counties in New York, covering approximately 1,935 total square miles.

Dataset Description: The New York FEMA 2017 LiDAR project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.71 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, Version 1.3. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to 2,477 individual 1,500-meter x 1,500-meter tiles, as tiled intensity imagery, and as tiled bare earth DEMs; all tiled to the same 1,500-meter x 1,500-meter schema. Continuous breaklines were produced in Esri file geodatabase format.

Ground Conditions: LiDAR was collected in spring of 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, Quantum Spatial, Inc. utilized a total of 44 ground control points that were used to calibrate the LiDAR to known ground locations established throughout the project area. An additional 129 independent accuracy checkpoints, 71 in Bare Earth and Urban landcovers (71 NVA points), 58 in Tall Weeds categories (58 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded the 2477 DEM files from the New York State GIS site. The data were downloaded from this URL: ftp://ftp.gis.ny.gov/elevation/DEM/FEMA_FultonSaratogaHerkimerFranklin2017/. The data were processed to the Data Access Viewer (DAV) and http. 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 are available for custom download at the link 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 DEMs. The purpose of these LiDAR data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 1-meter 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 = IMG

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 1.0 Meters

Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary

Any conclusions drawn from the analysis of this information are not the responsibility of 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 71 checkpoints located in bare earth and urban (non-vegetated) areas.

2. Vegetated Vertical Accuracy (VVA): VVA shall be reported for "tall weeds" land cover classes. The target VVA is: 29.4 cm 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. The VVA was tested with 58 checkpoints located in forested and tall weeds (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.

Tested 0.129 meters NVA at a 95% confidence level (6.6 cm RMSE) using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the DEM was calculated using 71 independent checkpoints located in the Bare Earth and Urban land cover categories. Tested 0.217 meters VVA was calculated using 58 checkpoints located in the Forested and Tall Weeds land cover categories at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for LiDAR Data. Tested against the DEM.

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 cover the entire area specified for this project.

Data were collected and processed by Quantum Spatial, Inc. for FEMA. The data were downloaded from the New York State GIS ftp site by the NOAA Office for Coastal Management (OCM) where the data were processed to make it available for custom download from the Data Access Viewer (DAV) and bulk download from https.