2015 Lidar DEM: Miami-Dade County, FL

Feb 15, 17, 18, 19, 20, 21, Apr 2, 3, 11, 12, 13, 2015

Link to custom download the DEM data from the Data Access Viewer(DAV).

Link to bulk download the DEM data.

Information on the NOAA Office for Coastal Management (OCM)

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to data set report.

Link to custom download the lidar point data from which these raster Digital Elevation Model (DEM) data were created.

Link to the hydro breaklines.

Link to the building footprint.

Link to the Tetra Tech re-processing report.

The project was divided in two phases: Collection and classification of LiDAR data; and building height extraction. The LiDAR data was collected utilizing a Riegl LMS-Q680i in a Cessna 206 from an approximate altitude of 1,800 feet above ground level, an approximate ground speed of 110 knots at a pulse rate repetition of 400kH, resulting in a minimum of 8.2 points per square meter. The sensor used a 60 degree field of view. The project was flown to have 50 percent overlap between swaths.

The Global Positioning System (GPS) data were processed using Applanix POSPac Mapping Suite version 7.8 using Smart Base method and single base methods. A fixed bias carrier phase solution was computed in forward and reverse directions. The LiDAR collection took place when Positional Dilution of Precision (PDOP) was at or below 3. Occasionally, the PDOP rose slightly above 3. This had no effect on the data. The GPS trajectory was combined with the IMU data using the Applanix POSPac software. The resulting Smoothed Best Estimate of Trajectory (SBET) was exported and used in Riegl RiProcess software to compute the laser mass point positions in Northing, Easting, and Elevations coordinates. The raw laser data were merged with the SBET using Riegl RiProcess software. The data set was processed using RiProcess, RiAnalyze, and RiWorld software where each flight line was processed to a point cloud. The data was adjusted flight line to flight line using Riegl’s Scan Data Adjustment tool to ensure a proper relative calibration match between flight lines. Each flight was checked for project coverage, data gaps between overlapping flight lines, point density and then exported in LAS 1.3 format.

The entire project was collected without gaps. The LAS files were projected to the NAD_1983_HARN_StatePlane_Florida_East_FIPS_0901_Feet and North American Vertical Datum of 1988 (NAVD88). Ellipsoidal heights were converted to orthometric heights using the current Geiod12A. The LAS files were imported to TerraSolid, LTD TerraScan software to be classified to bare earth ground and later feature coded to USGS specifications. The LAS files contain 8 classifications: 1 = unclassified; 2 = ground; 7 = noise points; 9 = water; 10 = buffered ground points surrounding breaklines; 12 = overlap; 15 = overpass and bridges.

The tiles dataset was imported to Digital Transfer Solutions EarthShaper® software to collect breaklines from LiDAR data. The single and double line linear hydrographic features were hydro-enforced with downhill constraints to model correct flow patterns. Water bodies were hydro-flattened to ensure uniform elevation across the feature. The data were adjusted flight line to flight line using Riegl’s Scan Data Adjustment tool to ensure a proper relative calibration match between flight lines. Each flight was checked for project coverage, data gaps between overlapping flight lines, point density and then exported in LAS 1.3 format. The LAS files were imported to TerraSolid, LTD TerraScan software to be classified to bare earth ground and later feature coded to USGS specifications.

DEMs were created using QCoherent LP360 software. The bare-earth LAS data was loaded into the software along with the tile layout and hydro shapefile collected from the LAS data set. DEMS were produced at a 5ft cell size and hydro-flattened. To QC the DEMs Global Mapper was used to check for completeness of the tiles and that the hydro features were flattened and represented correct elevations. Once the QC was complete the files were exported out of ArcGIS to create Arc DEMS. The LiDAR data was ran through an automated ground and building classification using terrascan software. A manual check of the building classification was done in LP360 and terrascan. The provided building shapefile was loaded and data cross sections were taking to check the classification of the outlined buildings. Once the manual check was completed the building LAS points were loaded into LP360 along with the building polygon shapefile supplied by ITD. In LP360 a confliction was ran to drape each building polygon to the max Z value of LAS data found in each polygon. To QC the auto process the building polygon shapefile was brought into ArcGIS using LP360 to take cross sections of the data to check the building polygon Z value. After all the building data was quality controlled and assured we joined the field height to complete the geodatabase BuildingPlanimetrics_from PSDE3.gdb provided by the county. Any building with a height value of 0 represents a building that did not exist in the LiDAR dataset. The building geodatabase remained as ITD provided it projected horizontally to the NAD_1983_ StatePlane_Florida_East_FIPS_0901_Feet, and vertically to the North American Vertical Datum of 1988 (NAVD88). COLLECTION DATES: 2/15/15, 2/17/15, 2/18/15, 2/19/15, 2/20/15, 2/21/15, 4/2/15, 4/3/15, 4/11/15/, 4/12/15, 4/13/15. 366 flight lines of data were collected.

The NOAA Office for Coastal Management (OCM) received 1798 topographic DEM files in img format from the Miami-Dade County Information Technology Department (ITD). The bare earth raster files were at a 5 ft grid spacing. The data were received in Florida State Plane East Zone 0901, NAD83 HARN coordinates and were in orthometric (NAVD88) elevations in US feet.

Upon receipt and review of the data from Miami-Dade County's ITD, NOAA OCM decided to improve the usability of the data by contracting out the re-classification of the lidar las files and accordingly, the re-creation of the DEM img files. The reclassification of the las files and creation of new DEM img files was done by Tetra Tech in August 2017.

Tetra Tech took delivery of the data from NOAA and began review on 29 August 2017. The data was initially reviewed for completeness using LP360 and ArcMap 10.2. Some gaps were found in the data and these were reported to NOAA. The LiDAR was then run through an initial classification, where Classes 3, 4, and 5 (Vegetation) were classed to Class 1 (Unclassified). Extraneous classes beyond the classification scheme were also identified and moved to an appropriate class. The LiDAR data was then run through a step designed to add to, and improve the Class 2 – Ground classified points, as well as provide improvement in the building class (Class 6). 5 foot DEMs were then created using LP360. These DEMs were reviewed for quality, and this review was used to correct the classification in the LAS point cloud, where needed. Final 5 foot DEMs were then created in LP360.

The NOAA Office for Coastal Management (OCM) received 1798 topographic DEM files in img format from Tetra Tech. The data remained in the Florida State Plane East Zone 0901, NAD83 HARN coordinates, orthometric (NAVD88) elevations in US feet and a 5 ft grid spacing. NOAA OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. Converted the raster files from img format to Cloud Optimized Geotiff format