2019 - 2020 USGS Lidar: Glacier Bay, AK (QL2)

Product: QL2 LAS 1.4

Geographic Extent: This NIR Lidar dataset and derived products encompass an area covering approximately 473,860 acres of South East Alaska. The Quality Level 2 (QL2) project area encompassed 345,212 acres of the total area.

Dataset Description :The Glacier Bay 3DEP Lidar project called for the planning, acquisition, and processing of Lidar data collected at an aggregate nominal pulse spacing (ANPS) of 0.71 meters for all QL2 areas. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on the NAD83(2011) horizontal datum and NAVD88 (GEOID12B) vertical datum. Data was projected in UTM Zone 8N. All units are in meters. RAW flight line swaths were processed to create 2,390 classified LAS 1.4 files delineated in 1,000 m x 1,000 m tiles. Please note that tiles GB_03743 and GB_05552 do not include valid point return data as they are entirely over areas of open water and thus have not been included in this submission. Each LAS file contains Lidar point information, which has been calibrated, controlled, and classified. Additional derived products include hydro-flattened DEMs, Highest Hit DSMs, Intensity Images, DZ Orthos, Flightline Shapes, Swath Coverage Shapes, Ground Survey Shapes and 3D breaklines of rivers and lakes within the study area.

Ground Conditions: Lidar was collected in summer 2019, while the presence of snow on the ground was at a minimum 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, DOWL on behalf of QSI established a total of 194 ground control points distributed throughout the Glacier Bay Delivery 1 project area. Lidar data was calibrated to these known ground locations. An additional 115 independent accuracy checkpoints, 33 in Bare Earth and Urban landcovers (NVA points) and 82 in Shrub, Tall Grass, and Forest categories (VVA points) were used to assess the vertical accuracy of the project data. These checkpoints were not used to calibrate or post process the data.

Note: currently only Delivery 1 of 2 has been released (Blocks 2 & 3, collected in 2019). When the second and final delivery is made available NOAA OCM will incorporate the data and update this metadata record.

The purpose of the Lidar data was to produce a high accuracy 3D dataset that meets all necessary standards laid out by the Glacier Bay contract. The raw Lidar point cloud data were used to create classified Lidar LAS files, hydro-flattened DEMs, Highest Hit DSMs, Intensity Images, DZ Orthos, Flightline Shapes, Swath Coverage Shapes and 3D breaklines of rivers and lakes within the study area.

CONTRACTOR: Quantum Spatial, Inc.

Ground Control Points were acquired by DOWL for Quantum Spatial Inc.

Data acquisition was coordinated by Quantum Spatial through Eagle Aerial. All Lidar data calibration, and follow-on processing were completed by Quantum Spatial.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.3",

"ldrsens" : "Riegl LMS Q1560",

"ldrmaxnr" : "Unlimited",

"ldrnps" : "0.50",

"ldrdens" : "4",

"ldranps" : "0.31",

"ldradens" : "10.69",

"ldrfltht" : "1,300",

"ldrfltsp" : "140",

"ldrscana" : "58.5",

"ldrscanr" : "Multiple Times Around",

"ldrpulsr" : "800",

"ldrpulsd" : "3",

"ldrpulsw" : "0.23",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1,456",

"ldrswato" : "50",

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

},

"ldraccur" : {

"ldrchacc" : "0",

"rawnva" : "0",

"rawnvan" : "0",

"clsnva" : "0",

"clsnvan" : "0",

"clsvva" : "0",

"clsvvan" : "0"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld (ignore) points are 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" : "NIR Water Surface"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

},

"lasclass" : {

"clascode" : "20",

"clasitem" : "Ignored Ground Near Breaklines"

},

"lasclass" : {

"clascode" : "22",

"clasitem" : "Temporal Exclusion Points"

}

}}

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

Data is available online for bulk or 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.

Applanix PosPac 7.1, Microstation Version 8.0, TerraScan Version 19, TerraModeler Version 19, TerraMatch Version 19, ESRI ArcGIS 10.5, Windows 10 Operating System

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

Absolute accuracy was assessed using Non-Vegetated Vertical Accuracy (NVA) reporting designed to meet guidelines presented in the FGDC National Standard for Spatial Data Accuracy. NVA compares known ground check point data that were withheld from the calibration and post-processing of the lidar point cloud to the triangulated surface generated by the unclassified lidar point cloud as well as the derived gridded bare earth DEM. NVA is a measure of the accuracy of lidar point data in open areas where the lidar system has a high probability of measuring the ground surface and is evaluated at the 95% confidence interval (1.96 * RMSE).

The mean and standard deviation (sigma) of divergence of the ground surface model from quality assurance point coordinates are also considered during accuracy assessment. These statistics assume the error for x, y and z is normally distributed, and therefore the skew and kurtosis of distributions are also considered when evaluating error statistics.

For the Glacier Bay, Alaska Delivery 1 survey, 33 ground check points were withheld from the calibration and post processing of the lidar point cloud, with resulting non-vegetated vertical accuracy of 0.073 meters as compared to unclassified LAS with 95% confidence. The RMSe = 0.037m.

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 data passes Non-Vegetated Vertical Accuracy specifications.

Classified LAS files were tested by QSI for both vertical and horizontal accuracy. All data is seamless from one tile to the next, no gaps or no data areas.

Data is backed up to tape and to cloud storage.