2015 Lidar: Miami-Dade County, FL

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

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Bulk download of data files in LAZ format, geographic coordinates, orthometric heights.

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 the breaklines.

Link to the large building footprint.

Link to custom download, from the Data Access Viewer (DAV), the raster Digital Elevation Model (DEM) data that were created from this lidar data set.

Link to the Tetra Tech re-processing report.

Aerial Cartographics of America, Inc.

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 Mobile Mapping Suite version 6.2 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 affect 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 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 1.2 format.

The entire project was collected without gaps. The files were projected to the NAD_1983_HARN_StatePlane_Florida_East_FIPS_0901_Feet, and National American Vertical Datum of 1988 (NAVD88). Ellipsoidal heights were converted to orthometric heights using the current Geoid12A. All units are U.S. Survey Feet. 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 degrees 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. A Digital Elevation Model (DEM) of the bare earth surface was created as a hydro-enforced 32-bit floating point grid format and constructed with a 5' cell size. ESRI ArcHydro was used to check the data met project specifications.

The NOAA Office for Coastal Management (OCM) received 1798 topographic files in las (version 1.3 format) from the Miami-Dade County Information Technology Department (ITD). The files contained lidar elevation, intensity, return number, classification, scan angle and adjusted GPS time measurements. The data were received in Florida State Plane East Zone 0901, NAD83 HARN coordinates and were vertically referenced to NAVD88 using the GEOID12A model. The vertical units of the data were US Survey feet. OCM noticed some inconsistencies in the classifications of the data and informed Miami-Dade County 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 original, unclassified data from Aerial Cartographics of America (ACA) were sent to Tetra Tech for the re-classification work. 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 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 files in las (version 1.4 format) from Tetra Tech. The files contained lidar elevation, intensity, return number, classification, scan angle and adjusted GPS time measurements. The data were received in Florida State Plane East Zone 0901, NAD83 HARN coordinates and were vertically referenced to NAVD88 using the GEOID12A model. The vertical units of the data were US Survey feet. NOAA OCM did not determine a new vertical accuracy for the re-classified data. The vertical accuracy value listed in this metadata record is the value for the original Miami-Dade County's ITD data. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The files were converted from las to laz using laszip.

2. LAStools lasinfo and lasvalidate were run for general QC checks. There were never classified points with erroneous GPS times. These points were dropped using LAStools (Adjusted GPS times above 300000000 and below 0 were dropped).

3. An internal OCM script was run to provide a list of the min and max z values per tile and a point classification count.

4. An internal OCM script was run to convert the las files from NAVD88 (GEOID12A) elevations to ellipsoidal elevations using GEOID12A, to convert from Florida State Plane East Zone 0901 (NAD83 HARN) to a geographic coordinate system, to convert from US Survey feet to meters, and to create laz files to database and to the http site.