2017 USGS Lidar: Palm Beach County, FL

Axis Geospatial, LLC collected 1,994 square miles in Palm Beach County, Florida. The nominal pulse spacing for this project was 1 point every 0.7 meters. Dewberry used proprietary procedures to classify the LAS according to project specifications: 1-Processed, but unclassified, 2- Bare-earth ground, 7-Low Noise (low, manually identified, if necessary), 9-Water, 10-Ignored Ground due to breakline proximity, 17- Bridge Decks, 18-High Noise (high, manually identified, if necessary). Dewberry produced 3D breaklines and combined these with the final lidar data to produce seamless hydro flattened DEMs for the project area. The data was formatted according to the tile naming convention provided by the client with each tile covering an area of 2,500 ft by 2,500 ft. A total of 9,222 LAS tiles and 9,222 DEM tiles were produced for the entire project.

In addition to these lidar point data, the hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record.

The purpose of this lidar data was to produce high accuracy 3D elevation products, including tiled lidar in LAS 1.4 format, 3D breaklines, and 2.5 foot cell size hydro flattened Digital Elevation Models (DEMs). All products follow and comply with USGS Lidar Base Specification Version 1.2.

A complete description of this dataset is available in the Final Project Report that was submitted to the U.S. Geological Survey.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "USGS-NGP Lidar Base Specification V1.2",

"ldrsens" : "Riegl LMS-Q1560",

"ldrmaxnr" : "unlimited",

"ldrnps" : "0.7",

"ldrdens" : "2.04",

"ldranps" : "0.7",

"ldradens" : "2.04",

"ldrfltht" : "907",

"ldrfltsp" : "140",

"ldrscana" : "58.52",

"ldrscanr" : "267",

"ldrpulsr" : "800",

"ldrpulsd" : "3",

"ldrpulsw" : "0.51",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1016",

"ldrswato" : "30",

"ldrcrs" : "NAD 1983 (2011) State Plane Florida East U.S. Survey Feet",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldraccur" : {

"ldrchacc" : "0.485",

"rawnva" : "0.104",

"rawnvan" : "79",

"clsnva" : "0.094",

"clsnvan" : "79",

"clsvva" : "0.180",

"clsvvan" : "61"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld points were identified in these files using the standard LAS Withheld bit",

"lasolap" : "Swath overage points were identified in these files using the standard LAS overlap bit",

"lasintr" : "16",

"lasclass" : {

"clascode" : "1",

"clasitem" : "Processed, but unclassified"

},

"lasclass" : {

"clascode" : "2",

"clasitem" : "Bare earth, ground"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored ground due to breakline proximity"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High noise"

}

}}

Any conclusions drawn from the analysis of this information are not the responsibility of USGS, NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk and custom downloads.

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

Microsoft Windows 7 Enterprise Service Pack 1; ESRI ArcCatalog 10.4.1

Only checkpoints photo-identifiable in the intensity imagery can be used to test the horizontal accuracy of the lidar. Photo-identifiable checkpoints in intensity imagery typically include checkpoints located at the ends of paint stripes on concrete or asphalt surfaces or checkpoints located at 90 degree corners of different reflectivity, e.g. a sidewalk corner adjoining a grass surface. The xy coordinates of checkpoints, as defined in the intensity imagery, are compared to surveyed xy coordinates for each photo-identifiable checkpoint. These differences are used to compute the tested horizontal accuracy of the lidar. As not all projects contain photo-identifiable checkpoints, the horizontal accuracy of the lidar cannot always be tested. Qualitative value: 0.485, Test that produced the valued: Lidar vendors calibrate their lidar systems during installation of the system and then again for every project acquired. Typical calibrations include cross flights that capture features from multiple directions that allow adjustments to be performed so that the captured features are consistent between all swaths and cross flights from all directions.

This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 1.35 ft (41 cm) RMSEx/RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 3.28 ft (1 meter) at a 95% confidence level.

Eight (8) checkpoints were photo-identifiable but do not produce a statistically significant tested horizontal accuracy value. Using this small sample set of photo-identifiable checkpoints, positional accuracy of this dataset was found to be RMSEx = 0.79 ft (24.1 cm) and RMSEy = 0.47 ft (14.3 cm) which equates to +/- 1.59 ft (48.5 cm) at 95% confidence level. While not statistically significant, the results of the small sample set of checkpoints are within the produced to meet horizontal accuracy.

The vertical accuracy of the classified lidar and final bare earth DEMs was tested by Dewberry with 140 independent survey checkpoints. The survey checkpoints are evenly distributed throughout the project area and are located in areas of non-vegetated terrain (79 checkpoints), including bare earth, open terrain, and urban terrain, and vegetated terrain (61 checkpoints), including forest, brush, tall weeds, crops, and high grass.The vertical accuracy of the lidar is tested by comparing survey checkpoints to a triangulated irregular network (TIN) that is created from the lidar ground points. Checkpoints are always compared to interpolated surfaces created from the lidar point cloud because it is unlikely that a survey checkpoint will be located at the location of a discrete lidar point. The vertical accuracy of the final bare earth DEMs is tested by extracting the elevation of the pixel that contains the x/y coordinates of the checkpoint and comparing these DEM elevations to the surveyed elevations. Accuracy results may vary between the source lidar and final DEM deliverable. DEMs are created by averaging several lidar points within each pixel which may result in slightly different elevation values at each survey checkpoint when compared to the source LAS, which is tested by comparing survey checkpoints to TINs. TINs do not average several lidar points together but interpolate (linearly) between two or three points to derive an elevation value. The accuracy results reported for the overall project are the accuracy results of the source lidar. Bare earth DEM accuracy results are reported in the DEM metadata file.

All checkpoints located in non-vegetated terrain were used to compute the Non-vegetated Vertical Accuracy (NVA). Project specifications required a NVA of 0.64 ft (19.6 cm) at the 95% confidence level based on RMSEz (0.33 ft/10 cm) x 1.9600. All checkpoints located in vegetated terrain were used to compute the Vegetated Vertical Accuracy (VVA). Project specifications required a VVA of 0.96 ft (29.4 cm) based on the 95th percentile.Qualitative value:0.094 0.180, Test that produced the value: The following result is from testing the source lidar data. DEM accuracy results are in the DEM metadata file.

This lidar dataset was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 0.33 ft (10 cm) RMSEz Vertical Accuracy Class. Actual NVA accuracy was found to be RMSEz = 0.16 ft (4.9 cm), equating to +/- 0.31 ft (9.4 cm) at 95% confidence level. The following result is from testing the source lidar data. DEM accuracy results are in the DEM metadata file.

This lidar dataset was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 0.33 ft (10 cm) RMSEz Vertical Accuracy Class. Actual VVA accuracy was found to be +/- 0.59 ft (18.0 cm)at the 95th percentile.

The 5% outliers consisted of 3 checkpoints that is larger than the 95th percentile. These checkpoints have DZ values ranging between 0.73 ft (22.3 cm) and 2.09 ft (63.7cm).

A visual qualitative assessment was performed to ensure data completeness and bare earth data cleanliness. No void or missing data and data passes vertical accuracy specifications.

Data covers the project boundary.

Data is backed up to tape and to cloud storage.