Data Management Plan (Deprecated)

St. Johns County, Florida (County) has developed a comprehensive countywide base mapping and GIS enhancements to support master drainage planning, transportation planning, and preliminary engineering and wetland preservation studies. As part of this effort, Woolpert was contracted by Jones, Edmunds & Associates (JEA) to develop the new imagery and new DTM. The project consists of new 6-inch 4-Band Orthoimagery, new 1-meter max LiDAR, new 1-foot contours, updating of topographic/planimetric features. This data set is one component of a digital terrain model (DTM) for St. Johns County. The dataset is comprised of mass points, 2-D and 3-D breakline features, 1-foot and 2-foot contours, ground control, vertical test points, and a footprint of the data set, in the ESRI ArcGIS File Geodatabase format. In accordance with the counties specifications, the following breakline features are contained within the database: closed water bodies (lakes, reservoirs, etc) as 3-D polygons; linear hydrographic features (streams, shorelines, canals, swales, embankments, etc) as 3-D breaklines; coastal shorelines as 3-D linear features; edge of pavement road features as 3-D breaklines; soft features (ridges, valleys, etc.) as 3-D breaklines; island features as 3-D polygons; concretedam, culvert, footprint, lowconfidence, lowconfidenceanno, overpass, pipe, roadcenterlineoverbridge and swamppoint as 2-D features. Contours were generated from LiDAR ground class and breaklines and meet National Map Accuracy Standards. The LiDAR masspoints are delivered in the LAS file format based on the Florida statewide 5,000' by 5,000' grid. The GEOID model used to reduce satellite derived elevations to orthometric height is GEOID12A. Breakline features were captured to develop a hydrologically correct DTM. The coastalshoreline has a constant value of -0.6’ that was statistically derived from the LiDAR point cloud collected within the 2-hour window of MLL tide. 2008 Hydrographic and soft features were used to supplement the 2013 breaklines in Low Confidence areas.

The NOAA Office for Coastal Management (OCM) received the lidar point data from St. Johns County GIS in March 2018 and processed the data to be available for download from the Data Access Viewer (DAV) and via https . OCM noted that many points that fall on buildings, bridge decks, light poles, cell phone towers, are classified as 5 - high vegetation.

In addition to these lidar point data, the bare earth Digital Elevation Models (DEM) created from the lidar point data are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

Planimetric and breakline data are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

Process Steps:

• Airborne terrestrial LiDAR was collected for St. Johns County, FL. The LiDAR system acquisition parameters were developed based on a maximum average ground sample distance of 3.23 feet. A Leica ALS70 LiDAR sensor was used for acquisition. Acquisition specifications for the sensor were as follows: Field of View (full angle) - 40 degrees, Nominal flight altitude (AGL) - 6500 feet, Airspeed - 172 mph (150 knots), Laser pulse rate - 270,000 Hz, Nominal swath width (on ground) - 4732 feet, Maximum cross track point spacing - 2.98 feet, Maximum along track point spacing - 3.01 feet, Average point spacing - 3.28 feet, Flight line spacing - 3314 feet, Side overlap - 29.3 percent. Prior to the LiDAR acquisition, the system underwent a system calibration to verify the operational accuracy and misalignment angles. LiDAR data acquisition only occurred when the sky was sufficiently clear of clouds, smoke, and atmospheric haze. The LiDAR data was processed immediately following the acquisition to verify the coverage had no voids. The GPS and IMU data was post processed using differential and kalman filter algorithms to derive a smoothed best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project. The ground control system to support the LiDAR survey consisted of 24 control points surveyed specifically for this project. The LiDAR data was post processed and verified to be consistent with the project requirements in terms of post spacing and absence of artifacts. The point cloud underwent classification to determine bare-earth points (class 2), low vegetation points (class 3), medium vegetation points (class 4), high vegetation points (class 5), building points (class 6) noise points (class 7), water returns (class 9), breakline proximity points (class 10), bridge points (class 13, canopy/covered walkway points (class 14) and unclassified data (class 1).
• 2019-03-25 00:00:00 - The NOAA Office for Coastal Management (OCM) received the data from the St. Johns County, Florida GIS Department. The data were in Florida State Plane East NAD83 (HARN) coordinates (US survey feet) and NAVD88 (Geoid12A) elevations in US survey feet. The data were classified as: 1 - Unclassified, 2 - Ground, 3 - Low vegetation, 4 - Medium vegetation, 5 - High vegetation, 6 - Buildings, 7 - Low Noise, 9 - Water,13 - Bridges, 14 - Canopy/covered walkway. OCM processed all classifications of points to the Digital Coast Data Access Viewer (DAV). Classes available on the DAV are: 1, 2, 3, 4, 5, 6, 7, 9, 13, 14. OCM noted that many points that fall on buildings, bridge decks, light poles, cell phone towers, are classified as 5 - high vegetation. OCM performed the following processing on the data for Digital Coast storage and provisioning purposes: 1. The LAStools software scripts lasinfo and lasvalidate were run on the laz files to check for errors. 2. The LAStools software script laszip was run on the las files to convert them to laz format. 3. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges. 4. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid 12A model, to convert from Florida State Plane East coordinates in feet to geographic coordinates, to convert from vertical units of feet to meters, to assign the geokeys, to sort the data by gps time and zip the data to database and to http.

Data is available online for bulk and custom downloads.