2016 - 2017 FEMA Lidar DEM: Franklin and St. Lawrence Counties and Oneida Sub-Basin, NY

Product: These are Digital Elevation Model (DEM) data for Franklin, Lewis, Madison, Oneida, Onondaga, Oswego, and St. Lawrence Counties, New York as part of the required deliverables for the New York 2016 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: Seven counties in New York, covering approximately 4,474 total square miles. East Zone AOI is Franklin and St. Lawrence Counties, Central Zone AOI is Lewis, Madison, Oneida, Onondaga, and Oswego Counties.

Dataset Description: New York FEMA 2016 QL2 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, Version 1.2. Lidar data was delivered as flightline-extent unclassified LAS swaths, as processed classified LAS 1.4 files formatted to 4,597 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. Contours with a 1-foot interval were produced in Esri file geodatabase format, tiled to the same 1,500-meter x 1,500-meter schema.

Ground Conditions: Lidar was collected in winter/spring of 2016/2017, 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. established a total of 76 ground control points that were used to calibrate the lidar to known ground locations established throughout the New York East Zone (Franklin and St. Lawrence Counties) project area. An additional 71 independent accuracy checkpoints, 71 in Bare Earth and Urban landcovers (59 NVA points), 59 in Forested, Brushland/Trees, and Tall Weeds/Crops categories (59 VVA points), were used to assess the vertical accuracy of the data. Quantum Spatial, Inc. established a total of 30 ground control points that were used to calibrate the lidar to known ground locations established throughout the New York Central Zone (Lewis, Madison, Oneida, Onondaga, and Oswego Counties) project area. An additional 68 independent accuracy checkpoints, 43 in Bare Earth and Urban landcovers (43 NVA points), 25 in Forested, Brushland/Trees, and Tall Weeds/Crops categories (25 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 5948 DEM files (4597 files for the East Zone AOI and 1351 files for the Central Zone AOI) from the New York State GIS site. The data were downloaded from these URLs: ftp://ftp.gis.ny.gov/elevation/DEM/FEMA_FranklinStLawrence2016/ and ftp://ftp.gis.ny.gov/elevation/DEM/FEMA_OneidaSubbasin2016/. 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 and the breaklines 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, raster DEMs, and contours. 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, hydro-flattened DEMs, and contours 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 (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.

East Zone (Franklin, St. Lawrence Counties)

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

1. Required NVA : 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in bare earth and urban land cover classes. This is a required accuracy. NVA was tested with 71 checkpoints located in bare earth and urban (non-vegetated) areas; points BE03 and UA01 were excluded as they fell outside project AOI.

2. Vegetated Vertical Accuracy (VVA): VVA reported for forested, brushland/trees, and tall weeds/crops land cover classes. Target VVA: 29.4 cm at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data, i.e., based on 95th percentile error in all vegetated land cover classes combined. This is a target accuracy. VVA was tested with 58 of 59 checkpoints located in forested, brushland/trees, and tall weeds/crops (vegetated) areas; point F023 excluded as it fell outside AOI. Checkpoints were distributed throughout project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. AccuracyZ 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 0.0827 meters NVA at a 95% confidence level (4.2 cm RMSE) using RMSE(z) x 1.9600 as defined by National Standards for Spatial Data Accuracy (NSSDA).

Tested 0.2549 meters VVA calculated using 58 checkpoints located in Forested, Brushland/Trees, and Tall Weeds/Crops land cover categories at 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data. Tested against DEM.

Central Zone (Lewis, Madison, Oneida, Onondaga, Oswego Counties)

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

1. Required NVA : 19.6 cm at 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in bare earth and urban land cover classes. This is a required accuracy. NVA was tested with 41 of 43 checkpoints located in bare earth and urban (non-vegetated) areas; points BE03 and UA01 excluded as they fell outside project AOI.

2. Vegetated Vertical Accuracy (VVA): VVA reported for forested, brushland/trees, and tall weeds/crops land cover classes. The target VVA: 29.4 cm at 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data, i.e., based on 95th percentile error in all vegetated land cover classes combined. This is a target accuracy. The VVA tested with 21 of 25 checkpoints located in forested, brushland/trees, and tall weeds/crops (vegetated) areas; points FO01, FO02, FO03, FO11 and FO16 excluded as they fell outside the AOI. The checkpoints were distributed throughout project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. AccuracyZ 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 0.1030 meters NVA at 95% confidence level (5.3 cm RMSE) using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA).

Tested 0.1182 meters VVA calculated using 23 checkpoints located in Forested, Brushland/Trees, and Tall Weeds/Crops land cover categories at 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data. Tested against 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 covers the entire area specified for this project.

Data were collected and processed by Quantum Spatial, Inc. for FEMA. The DEM 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.