2017 USGS QL1 Lidar DEM: Fairbanks, AK

No metadata record was provided for this digital elevation model (DEM) dataset. The information provided here was taken from the Quantum Spatial, Inc. lidar report. A link to this report is provided in the URL section of this metadata record.

In May 2017, Quantum Spatial (QSI) was contracted by the United States Geological Survey (USGS) to collect QL1 and QL2 Light Detection and Ranging (LiDAR) data over approximately 1.8 million acres of land for the Fairbanks 3DEP mapping site in Alaska (Task Order G17PD00606). This metadata record references the QL1 portion of the larger dataset. Data were collected to aid USGS in assessing the topographic and geophysical properties of the study area to support the 3DEP mapping initiative.

Geographic Extent: The QL1 area encompasses 248,555 acres

Dataset Description: RAW flight line swaths were processed to create classified LAS 1.4 files delineated in 3000 x 3000 ft tiles tiles. Each LAS file contains LiDAR point information, which has been calibrated, controlled, and classified. LAS files have been edited to the extent of the buffered boundary. Additional derived products include intensity images, hydro-flattened DEMs, highest hit surface models, 2ft contours, and 3D breaklines of rivers and lakes within the study area.

Ground Conditions: Data was acquired during conditions with an absence of snow, high water, ground fog and/or clouds below the flight altitudes.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

The purpose of the lidar data was to produce a high accuracy 3D dataset that meets all necessary standards laid out by the 3DEP initiative.

The raw lidar point cloud data were used to create classified lidar LAS files, intensity images, hydro-flattened DEMs, highest hit surface models, 2ft contours, and 3D breaklines of rivers and lakes within the study area.

CONTRACTOR: Quantum Spatial, Inc.

Ground Control Points were acquired DOWL Engineering. All Lidar data acquisition, calibration, and follow-on processing were completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "National Geospatial Program Lidar Base Specification Version 1.2",

"ldrsens" : "ALS-70",

"ldrmaxnr" : "15",

"ldrnps" : ".71",

"ldrdens" : "2",

"ldranps" : "0.71",

"ldradens" : "2",

"ldrfltht" : "1600",

"ldrfltsp" : "145",

"ldrscana" : "30",

"ldrscanr" : "50.2",

"ldrpulsr" : "175",

"ldrpulsd" : "9",

"ldrpulsw" : "2.698",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "22",

"ldrswatw" : "857",

"ldrswato" : "28",

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

},

"ldraccur" : {

"ldrchacc" : "0.5",

"rawnva" : "0.376 ft",

"rawnvan" : "321"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld points are identified using the standard LAS witheld bit.",

"lasolap" : "Swath overage points are identified 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 (0.5m - 2m)"

},

"lasclass" : {

"clascode" : "4",

"clasitem" : "Medium Vegetation (2m - 6m)"

},

"lasclass" : {

"clascode" : "5",

"clasitem" : "High Vegetation (6m+)"

},

"lasclass" : {

"clascode" : "6",

"clasitem" : "Buildings (automated classification only)"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low Noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground Near Breakline"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge Decks"

}

}}

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

LASTools, TerraPOS, Cloudpro 1.2.4, Microstation Version 8i, TerraScan Version 17, TerraModeler Version 17, ESRI ArcGIS 10.3, Windows 7 Operating System

For the Fairbanks, Alaska QL1 survey, 125 quality assurance points were collected by DOWL, resulting in a non-vegetated vertical accuracy of 0.305 feet (0.093 meters), or 4.7 cm RMSE as compared to the bare earth DEM.

Vertical accuracy was also evaluated using Vegetated Vertical Accuracy (VVA) reporting. VVA compares known ground check point data collected over vegetated surfaces using land class descriptions to the triangulated ground surface generated by the ground classified LiDAR points. VVA is evaluated at the 95th percentile. For the Fairbanks, Alaska QL1 survey, 56 vegetated check points were collected by DOWL, with resulting vegetated vertical accuracy of 0.611 feet (0.186 meters), evaluated at the 95th percentile.

LAS files include all data points collected. No points have been removed or excluded. Shaded relief images have been visually inspected for data errors such as pits, border artifacts, and shifting. LiDAR flight lines have been examined to ensure consistent elevation values across overlapping flight lines. The raw point cloud is of good quality and data passes 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.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.