2018 USGS Lidar: Prince of Wales Island - Phase 2, AK

Product: These lidar data are processed Classified LAS 1.4 files, formatted to individual 1000 m x 1000 m tiles; used to create intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

Geographic Extent: 1 partial census area and 1 partial borough in Alaska, covering approximately 1198 total square miles.

Dataset Description: The Prince of Wales Phase II 2018 project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, Version 1.2. The data were developed based on a horizontal projection/datum of NAD 1983 2011 UTM Zone 8N, Meters and vertical datum of NAVD88 GEOID 12B, Meter. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to 3977 individual 1000 m x 1000 m tiles, as tiled 2000 m x 2000 m intensity imagery, and as tiled 2000 m x 2000 m bare earth DEMs (all delivered as 1145 individual 2000 m x 2000 m tiles, except for LAS tiles). Continuous breaklines were produced in Esri file geodatabase format.

Ground Conditions: LiDAR was collected in spring and summer 2018, while minimal snow was on the ground and rivers were at or below normal levels. In order to post process the LiDAR data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Quantum Spatial, Inc. utilized 231 independent accuracy checkpoints, 103 in Bare Earth and Urban landcovers (103 NVA points), 128 in Tall Weeds categories (128 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded this data set from this USGS site:

ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/

The datasets downloaded were:

USGS_LPC_AK_POW_P2_2018_LAS_2019/ Number of files: 3385

USGS_LPC_AK_POW_P2_TL_2018_LAS_2019/ Number of files: 570

These files were processed to the Data Access Viewer (DAV) and https. The total number of files downloaded and processed was 3955.

Hydro breaklines and building footprints 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.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create intensity images, breaklines and raster DEMs. The purpose of these LiDAR data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 0.5 meter cell size. These raw LiDAR point cloud data were used to create classified LiDAR LAS files, intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

Contract No. G16PC00016, Task Order No. 140G0218F0180; CONTRACTOR: Quantum Spatial,

Inc.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "USGS-NGP Base Specification v1.2",

"ldrsens" : "Riegl VQ1560i",

"ldrmaxnr" : "unlimited",

"ldrnps" : "0.35",

"ldrdens" : "8.0",

"ldranps" : "0.35",

"ldradens" : "8.16",

"ldrfltht" : "1300",

"ldrfltsp" : "150",

"ldrscana" : "29",

"ldrscanr" : "178",

"ldrpulsr" : "800",

"ldrpulsd" : "3",

"ldrpulsw" : "0.23",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.18",

"ldrswatw" : "1441.0",

"ldrswato" : "60",

"ldrgeoid" : "GEOID 12B",

"ldrcrs" : "NAD 1983 2011 UTM Zone 8N, Meter"

},

"ldraccur" : {

"ldrchacc" : "0",

"rawnva" : "0.162",

"rawnvan" : "103",

"clsnva" : "0.152",

"clsnvan" : "103",

"clsvva" : "0.281",

"clsvvan" : "128"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld (ignore) 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" : "3",

"clasitem" : "Low Vegetation"

},

"lasclass" : {

"clascode" : "4",

"clasitem" : "Medium Vegetation"

},

"lasclass" : {

"clascode" : "5",

"clasitem" : "High Vegetation"

},

"lasclass" : {

"clascode" : "6",

"clasitem" : "Buildings"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low Noise"

},

"lasclass" : {

"clascode" : "8",

"clasitem" : "Model Key Points"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

},

"lasclass" : {

"clascode" : "21",

"clasitem" : "Snow (where identifiable)"

}

}}

Any conclusions drawn from the analysis of this information are not the responsibility of Quantum Spatial, Inc., AK Dept of Natural Resources, 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.

MicroStation Version 8; TerraScan Version 18; TerraModeler Version 18; GeoCue Version 2017.1.14.1; Esri ArcGIS 10.3; Global Mapper 19; RiProcess 1.8.5; Windows 10 Operating System \\point_cloud\tilecls\*.las

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for raw LiDAR point cloud swath files. The required accuracy (ACCz) is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the "bare earth" and "urban" land cover classes.

The NVA was tested with 103 checkpoints located in bare earth and urban (non-vegetated) areas. These checkpoints were not used in the calibration or post processing of the LiDAR point cloud data. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. Elevations from the unclassified LiDAR surface were measured for the x,y location of each checkpoint. Elevations interpolated from the LiDAR surface were then compared to the elevation values of the surveyed control points. AccuracyZ has been tested to meet 19.6 cm or better.

Non-Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

Tested 0.162 meters NVA at a 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the raw LiDAR point cloud swath files was calculated against TINs derived from the final calibrated and controlled swath data using 103 independent checkpoints located in Bare Earth and Urban land cover classes.

These LAS data files include all data points collected. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The raw point cloud is of good quality and the data pass Non-Vegetated Vertical Accuracy specifications.

Data cover the entire area specified for this project.

Data is backed up to tape and to cloud storage.

Data collected by Quantum Spatial, Inc. for the Alaska Dept of Natural Resources. OCM downloaded the data from the USGS rockyftp site and processed to the Data Access Viewer (DAV).