2008 FEMA Lidar: South Oneida County (NY)

For Oneida County, NY, there were two types of elevation datasets. The first type is LiDAR and the second one is Auto-correlation DEM. Auto-correlation DEM data was developed wherever LiDAR data was not available. LiDAR data was made available to this project through two different initiatives. The first set of LiDAR data was made available through HMTAP-1650 project, which consisted of area of 3 miles buffers around Mohawk River. Though data was available for the whole length of Mohawk, only data that pertained to the county was used for this project.The second set of LiDAR data was made available for DFIRM. DFIRM data was delivered at two different times. The first delivery done in 2008 (covers middle part of the county) and the second delivery done in 2009 (covers a small area in the west, around Oneida lake). As the two coverages did not have issues dealing with overlaps, they were used as they are. For the auto correlated data, in an effort to provide an alternative to the collection of LiDAR data and utilization of the National Elevation Dataset (NED), Dewberry has tested the methodology for the generation of a photogrammetrically derived surface model appropriate for Hydrologic and Hydraulic modeling and conforming to FEMA standards.The autocorrelated surface was generated using imagery from the 2003 New York statewide collection along with the Aerial Triangulation (AT) solution provided with the source imagery. The surface was subsequently edited through manual processes and improved with breaklines in order to meet ASPRS Class 1 accuracy requirements for 4 foot contour mapping.The final terrain is named as Oneida_Terrain.gdb. Please check the image from the PDF report in the General folder of the MIP submitted data.

Terrain data is used to represent the topography of a watershed and/or floodplain environment and to extract useful information for hydraulic and hydrologic models. (Source: FEMA Guidelines and Specs, Appendix N).

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A footprint of this data set may be viewed in Google Earth at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/5044/supplemental/ny2008_fema_oneida_south_m5044.kmz

The project report of this data set may be viewed in Google Earth at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/5044/supplemental/ny2008_fema_oneida_south_m5044_lidarreport.pdf

LiDAR point data in LAS 1.0 format

ASPRS cassfication scheme (1 = undefined; 2 = ground) contains the following fields of information:

Class, GPS WeekTime, Easting, Northing, Elevation, Echo, Number, Echo, Intensity, Flightline

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Any conclusions drawn from the analysis of this information are not the responsibility of FEMA, NYSDEC, NOAA, the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=5044;

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The data depicts the elevations at time of survey and are accurate only for that time. Exercise professional judgement in using this data.

The LiDAR data vertical accuracy is in compliance with the National Standard for Spatial Data Accuracy (NSSDA) RMSE estimation of elevation data in support of 2ft. contour mapping products as it is referenced in the FEMA guidelines for flood hazard mapping, appendix A (see Cross References). The Sanborn Map Company has performed a data accuracy validation and found this data to be in compliance.Additionaly, The New York State Department of Environmental Conservation performed a ground control analysis of the Oneida LiDAR data using ground control checkpoints in several land cover classes and found the resultant RMSE in the exposed ground class to be within the contract specifications of 0.185 meters.For the auto correlated data, data were compiled to meet ASPRS Class 1 accuracy requirements for 4 ft contour mapping. the vetical accuracy value is 1.18 meters. For HMTAP the elevation meets the accuracy required for this project (accuracy equivalent to 2 ft contours according to FEMA Guidelines and Specifications for Flood Hazard Mapping.

Partners).; Quantitative Value: 0.185 meters, Test that produced the value: For the Oneida County Lidar data - Vertical error associated with this LiDAR data is a function of several factors including acquisition practices, height of the sensor above terrain, point spacing, diameter of the pulse footprint, network control station coordinates, kinematic GPS solutions, IMU calibration and post-processing functions.; Quantitative Value: 1.18 meters, Test that produced the value: For the autocorrelated data the resultant RMSE of this check was 1.18 meters; Quantitative Value: 0.60 meters, Test that produced the value: For the auto correlated data, when verifified against the control points identified by NY DOT the absolute accuracy of the surface model is 1.18 m RMSE. However, extensive evaluation was performed against the stereo imagery from which the surface was created and a relative accuracy of .39 m RMSE was achieved. Therefore the majority of the error present in the absolute accuracy is attributable to the error that is inherent in the AT solution for the source imagery.For HMTAP both methods(NDEP and RMSE)were utilised for vertical accuracy testing, LiDAR data over all three river basins(Susquehanna, Delaware and Mohawk) meets and exceeds all specifications.

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The 2009 Oneida County LiDAR data has met all quality checks in terms of relative accuracy, absolute accuracy, coverage and point and file format. The relative accuracy of the LiDAR data refers to how well the data set matches within itself. That is to say, adjacent LiDAR scans are in alignment with each other with no vertical or horizontal shifts caused by improper calibration and/or georeferencing. The absolute elevation has been validated by both Sanborn and NYS DEC.This was done by comparing the LiDAR ground surface against known ground control points. The data file format and point attribution is in compliance with the LAS version 1.1 specifications (see ASPRS LAS1.1 cross reference).The auto correlated data covers the mapping boundary provided for the Oneida County Auto-Correlation area. All files delivered were verified and tested to ensure they open and are positioned properly.The overall final Oneida correlated surface is free of artifacts caused by trees and buildings. Some minor artifacts from editing that do not negatively impact the the elevation of the final surface remain. For the HMTAP data Overall the data exhibit excellent detail and meet both the absolute and relative accuracy. The level of cleanliness for a bare-earth terrain is of the highest quality and no major anomalies were found.