2014 U.S. Geological Survey CMGP LiDAR: Post Sandy (Virginia)

USGS Contract Number: G10PC00093, Task Order: G14PD00222

Digital Aerial Solutions LLC was tasked to collect and process 4607 sq. miles of Light Detection and Ranging (LiDAR) dataset in Virginia. The LiDAR Survey encompasses 4607 sq. miles of area in Eastern Virginia inclusive of the counties and cities of Spotsylvania, Caroline, Hanover, Henrico, Chesterfield, Dinwiddie, Sussex, Richmond City, Hopewell City, Colonial Heights City, Petersburg City, portions of Orange and Louisa, Amelia, Nottoway and Prince Edward. The LiDAR point cloud was flown at a nominal post spacing of 0.7 meters for un-obscured areas. The LiDAR data and derivative products produced are in compliance with the U.S. Geological Survey National Geospatial Program Guidelines and Base Specifications, Version 1.0. The final LAS point cloud classified as 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 10-Ignored Ground due to breakline proximity, 17-overlap ground points and 18 - overlap unclassified points.

The GPS Survey was completed by ESP Associates for 3 block acquisition area, and 2 blocks acquisition area by Michale Baker Surveying totaling 4607 square miles through the project area.

Breaklines were delivered with the lidar dataset. These have not been reviewed by NOAA OCM, therefore are only available by request.

Evaluation of coastal storm damage impacts; aid in post-event reconstruction, and mitigation planning for future events, and collect LiDAR for counties heavily impacted by storm and flooding for which data is incomplete or inadequate to conduct proper analysis, as part of USGS Hurricane Sandy Response.

10779

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4970/supplemental/va2014_usgs_cmgp_sandy_m4970.kmz

A report for this the project may be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4970/supplemental/va2014_usgs_cmgp_sandy_m4970_lidarreport.pdf

A survey report for this the project may be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4970/supplemental/va2014_usgs_cmgp_sandy_m4970_qualityreport.pdf

LiDAR points in LAS format (ASPRS Classes 1,2,7,9,10,17,18)

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Any conclusions drawn from the analysis of this information are not the responsibility of Digital Aerial Solutions LLC, USGS, 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=4970;

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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. These data depict the heights at the time of the survey and are only accurate for that time.

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

Newly processed vectors were entered into the StarNet Least Squares adjustment program holding the NAD83-2011(epoch 2010) CORS and existing monumented NGS published coordinates, along with the inclusion of the Geoid12A model. A horizontal accuracy of 2nd Order Class I (1:50,000) and the vertical NAVD88 accuracy at 3rd Order (+/- 0.06') were achieved.+

There is not a systematic method of testing when testing horizontal accuracy in LiDAR. However this is tested during calibration of the sensor and is rechecked during the comparing of parallel and perpendicular flight lines. Additionally the horizontal accuracy is checked by collecting building corners during the survey. Lines are then digitized representing the building outline and the differences are measure from each individual survey point to the corner of the building outline. Stats are calculated to ensure horizontal tolerances are met. These measurements resulted in an RMSE of .42 meters and equals a .73 meter horizontal accuracy at the 95 % confidence level. Accuracy defined by NSSDA at the 95 % confidence level would be multiplier by 1.7308 times the RMSE.

The accuracy assessment was performed using the NSSDA standard method to compute the root mean square error (RMSE) based on a comparison of ground control points (GCP) and filtered LiDAR data points. Filtered LiDAR data has had vegetation and cultural features removed and by analysis represent bare earth elevations.

Testing was performed prior to gridding of the filtered LiDAR data points and construction of the 32-bit ERDAS Imagine format bare earth tiles. The RMSEz figure was used to compute the vertical National Standard for Spatial Data Accuracy (NSSDA). A spatial proximity analysis was used to select edited LiDAR data points contiguous to the relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error and adequate sample size.

(7.5 cm) 0.2806 ft RMSE; Quantitative Value: 0.147 meters, Test that produced the value: Tested 14.7 cm (0.55 ft.) fundamental vertical accuracy (FVA) at the 95% confidence level in open terrain, based on RMSEz x 1.9600. Tested against the DEM.; Quantitative Value: 0.202 meters, Test that produced the value: Tested 20.2 cm supplemental vertical accuracy (SVA) at the 95th percentile in Tallweed categories. Tested against the DEM.; Quantitative Value: 0.205 meters, Test that produced the value: Tested 20.5 cm supplemental vertical accuracy (SVA) at the 95th percentile in Brush Land catagories. Tested against the DEM.; Quantitative Value: 0.231 meters, Test that produced the value: Tested 23.1 cm supplemental vertical accuracy (SVA) at the 95th percentile in Forested catagories. Tested against the DEM.; Quantitative Value: 0.166 meters, Test that produced the value: Tested 16.6 cm supplemental vertical accuracy (SVA) at the 95th percentile in urban catagories. Tested against the DEM.; Quantitative Value: 0.187 meters, Test that produced the value: Tested 18.7 cm consolidated vertical accuracy (CVA) at the 95th percentile in all categories of data. Tested against the DEM.

GPS points were taken for five separate classes on flat or uniformly sloping terrain at least five meters away from any breakline. Output results are in NAD83-2011(epoch 2010) and UTM Zone 18, in meters, and VA State Plane North, in feet. There were a total 250 points in this Geodetic network. There are 18 existing and CORS marks utilized to control this network. There are 104 Control Points (CP), 29 Bear Earth, 25 Tall Weeds, 26 Brush areas, 26 Canopy (forest), , and 22 Urban locations. The vegetation height ranges were 0 - 0.5ft, 0.5 - 5ft, 5 - 6.5ft, > 6.5ft, 0 ft, respectively.

Digital Aerial Solutions LLC was tasked to collect and process 4607 sq. miles of Light Detection and Ranging (LiDAR) dataset in Virginia. The LiDAR Survey encompasses 4607 sq. miles of area in Eastern Virginia inclusive of the counties and cities of Spotsylvania, Caroline, Hanover, Henrico, Chesterfield, Dinwiddie, Sussex, Richmond City, Hopewell City, Colonial Heights City, Petersburg City, portions of Orange and Louisa, Amelia, Nottoway and Prince Edward. The LiDAR point cloud was flown at a nominal post spacing of 0.7 meters for un-obscured areas. The LiDAR data and derivative products produced are in compliance with the U.S. Geological Survey National Geospatial Program Guidelines and Base Specifications, Version 1.0. The final LAS point cloud classified as 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 10-Ignored Ground due to breakline proximity, 17-overlap ground points and 18 - overlap unclassified points.

The GPS Survey was completed by ESP Associates for 3 block acquisition area,

and 2 blocks acquisition area by Michale Baker Surveying totaling 4607 square miles through the project area.