Data Management Plan

This report pertains to a Specific Purpose LiDAR Survey of Nassau County, Florida. The LiDAR aerial acquisition was conducted by Terrapoint USA

between August 18, 2007 and September 4, 2007, and the breaklines and contours were subsequently generated by Dewberry. The PDS team is under

contract HS-34-14-00-22-469 with the Florida Division of Emergency Management (FDEM) and offered LiDAR and derived products as an add-on

agreement with Nassau County at the same rates as negotiated for the FDEM contract and utilizing the same Baseline Specifications from FDEM.

The LiDAR dataset of Nassau County was acquired by Terrapoint USA and processed to a bare-earth digital terrain model (DTM) in accordance with FDEM

Baseline Specifications. Detailed breaklines and contours were also produced by the PDS team. Each tile covers an area of 5000 ft by 5000 ft.

The FDEM Baseline Specifications require a maximum LiDAR post spacing of 4 feet, i.e., an average point density of less than 1 point per square meter.

However, the PDS team required a much higher point density of its subcontractors in order to increase the probability of penetrating dense foliage;

with nominal post spacing of 0.7 meters per flight line and 50% sidelap between flight lines, the average point density is 4 points per square meter

with higher point density there is a greater probability of penetrating dense vegetation and minimizing areas defined as "low confidence areas."

LiDAR was delivered as a point cloud in LAS 1.1 format.

Original contact information:

Contact Org: Florida DEM

Phone: 850-413-9907

Email: gis@dca.state.fl.us

Process Steps:

• 2008-01-01 00:00:00 - The ABGPS, IMU, and raw Optech 3100ea LiDAR scans are integrated using Optech Incorporated's DASHMap, version 1.1 software, Terrascan software and Microstation software. The resultant file is in a LAS binary file format. The LAS file version 1.1 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#, intensity value, xyz, etc.). The resultant points are referenced to the NAD83 horizontal datum and GRS80 vertical datum. The date and time for each flight line can be determined using the Julian date and time. The Julian date is a continuous count of days and fractions since noon Universal Time on January 1, 4713 BCE on the Julian Calendar.
• 2008-01-01 00:00:00 - The unedited data are classified to facilitate the application of the appropriate feature extraction filters. A combination of proprietary filters are applied as appropriate for the production of bare earth digital terrain models (dtms). 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. The LiDAR mass points were delivered in American Society for Photogrammetry and Remote Sensing LAS 1.1 format. The header file for each dataset is complete as define by the LAS 1.1 specification. In addition the following fields are included (Precision reported in brackets): Class (Integer); GPS Week Time (0.0001 seconds); Easting (0.01 meter); Northing (0.01 meter); Elevation (0.01 meter); Echo Number (Integer 1 to 4); Echo (Integer 1 to 4); Intensity (8 Bit Integer); Flightline (Integer); Scan Angle (Integer Degree). The LAS files do not include overlap. The data was classified as follows: Class 1 = Unclassified. This class includes vegetation, buildings, noise etc. Class 2 = Ground Class 7 = Noise Class 9 = Water
• 2010-10-20 00:00:00 - The NOAA Office for Coastal Management (OCM) received the files in las format. The files contained Lidar elevation and intensity measurements. The data were in projected in Florida State Plane Coordinates (East Zone, NAD83/HARN), and referenced to the orthometric datum of NAVD88 utilizing Geoid 03. OCM performed the following processing to the data to make it available within the Digital Coast: 1. The data were converted from State Plane Coordinates (NAD83/HARN) coordinates to geographic coordinates (NAD83). 2. The data were converted from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid 03. 3. The LAS data were sorted by latitude and the headers were updated.