Data Management Plan

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.

Process Steps:

• 2014-04-02 00:00:00 - The primary collection of LiDAR data was done by two Cessna 421 aircrafts. There were three LiDAR sensors used to acquire this mission; ALS60, ALS70 and an Optech Pegasus system. 35 flight missions were required to collect the entire area of the project area. The ABGPS, inertial measurement unit (IMU), and raw scans are collected during the LiDAR aerial survey. The ABGPS monitors the xyz position of the sensor and the IMU monitors the orientation. During the aerial survey, laser pulses reflected from features on the ground surface are detected by the receiver optics and collected by the data logger. GPS locations are based on data collected by receivers on the aircraft and base stations on the ground. The ground base stations are placed no more than 40 km radius from the flight survey area.
• 2014-04-10 00:00:00 - The ABGPS, IMU, and raw scans are integrated using proprietary software developed by Leica and delivered with the Leica System. The resultant file is in a LAS binary file format. The LAS version 1.2 file format can be easily transferred from one file format to another. It is a binary file format that maintains information specific to the LiDAR data (return number, intensity value, xyz, etc.). The resultant points are produced in UTM18/ NAD83 coordinate system, with units in Meters and Vertical datum referenced to the NAVD88 datum. The LiDAR mass points were processed in American Society for Photogrammetry and Remote Sensing LAS 1.2 format. The header file for each dataset is complete as defined by the LAS 1.2 specification. The datasets were divided into 1500 Meters by 1500 Meters tiling scheme, based on United States National Grid Index. The tiles are contiguous, do not overlap, and are suitable for seamless topographic data mosaics that include no "no data" areas.
• 2014-04-25 00:00:00 - The unedited data are classified to facilitate the application of the appropriate feature extraction filters. Digital Aerial Solutions used Terrasolids Terrascan and Terramodel softwares to classify and edit the LAS data and a combination of proprietary filters are applied as appropriate for the production of bare earth digital elevation models (DEMs). Interactive editing methods are applied to those areas where it is inappropriate or impossible to use the feature extraction filters, based upon the design criteria and/or limitations of the relevant filters. These same feature extraction filters are used to produce elevation height surfaces. DAS classified the LAS data as follows: Class 1 = Unclassified. This class includes vegetation, buildings, noise etc. Class 2 = Ground Class 7 = Noise Class 9 = Water Class 10 = Ignored Ground Class 17 = overlap ground Class 18 = overlap unclassified
• 2014-05-22 00:00:00 - Filtered and edited data are subjected to rigorous QA/QC, A series of quantitative and visual procedures are employed to validate the accuracy and consistency of the filtered and edited data. Ground control is established by DAS and GPS-derived ground control points (GCPs) in various areas of dominant and prescribed land cover. These points are coded according to land cover, surface material, and ground control suitability. A suitable number of points are selected for calculation of a statistically significant accuracy assessment, as per the requirements of the National Standard for Spatial Data Accuracy. A spatial proximity analysis is used to select edited LiDAR data points within a specified distance of the relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error, and adequate sample size. Accuracy validation and evaluation is accomplished using proprietary software to apply relevant statistical routines for calculation of Root Mean Square Error (RMSE) and the National Standard for Spatial Data Accuracy (NSSDA), according to Federal Geographic Data Committee (FGDC) specifications.
• 2014-05-25 00:00:00 - The Bare Earth DEM was extracted from the raw LIDAR products and attributed with the bare earth elevation for each cell of the DEM. Bare Earth DEMs do not include buildings, vegetation, bridges or overpass structures in the bare earth model. Where abutments were clearly delineated, this transition occurred at the junction of the bridge and abutment. Where this junction was not clear, the extractor used their best estimate to delineate the separation of ground from elevated bridge surface. In the case of bridges over water bodies, if the abutment was not visible, the junction was biased to the prevailing stream bank so as not to impede the flow of water in a hydrographic model. Bare earth surface includes the top of water bodies not underwater terrain, if visible.
• 2016-05-01 00:00:00 - The NOAA Office for Coastal Management (OCM) received the topographic files in classified LAZ format from USGS' ftp site. The data were received in UTM Zone 18N NAD83 coordinates (meters) and vertically referenced to NAVD88 using the Geoid12a model in meters. OCM performed the following processing for data storage and Digital Coast provisioning purposes: 1. LAS files were compressed to LAZ format with LASTools. 2. LAS files were removed of any duplicated points and extraneous points were reclassified to noise. 3. The LAS files were transformed to geographic (decimal degrees), ellipsoidal coordinates (meters) referenced to the Geoid12a model.

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

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4970;