2016 USGS QL2 Lidar: Connecticut River Basin, VT

Product: These lidar data are processed classified LAS 1.4 files, formatted to 4,149 individual 1,400-meter x 1,400-meter tiles and converted to Entwine Point Tiles format.

Geographic Extent: Several counties within the Connecticut River Basin in northeastern Vermont, covering approximately 2,858 square miles.

Dataset Description: The Connecticut River Basin, Vermont 2016 QL2 Lidar project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83 (2011) State Plane Vermont, meters and vertical datum of NAVD88 (Geoid 12B), meters. The data was reprojected to Web Mercator (EPSG:3857) when converting to Entwine Point Tile format.

Ground Conditions: Lidar was collected in Fall 2016, while no 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. established a total of 57 ground control points that were used to calibrate the lidar to known ground locations established throughout the Connecticut River Basin, VT project area. An additional 149 independent accuracy checkpoints, 84 in Bare Earth and Urban landcovers (84 NVA points), 65 in Forested, Shrubs, and Tall Weeds categories (65 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

NOAA produced this metadata, from the original USGS metadata, to support use by the Digtial Coast Data Access Viewer. Descrepancies were noted regarding the original projection units. However, the Entwine Point Tile data being leveraged in Web Mercator projection is in meters.

This high resolution lidar data will support the state of Vermont and local governments in their efforts regarding activities in the identified area. 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 0.7-meter cell size. These raw lidar point cloud data were used to create classified lidar LAS files, intensity images, 3D breaklines, hydro-flattened and hydro-enforced DEMs, digital surface models, and contours as necessary.

USGS Contract No. G16PC00016 CONTRACTOR: Quantum Spatial, Inc. Lidar data were acquired by Quantum Spatial, Inc. All follow-on processing was completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

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

"ldrsens" : "Leica ALS",

"ldrmaxnr" : "4",

"ldrnps" : "0.68",

"ldrdens" : "2.14",

"ldranps" : "0.68",

"ldradens" : "2.14",

"ldrfltht" : "2000",

"ldrfltsp" : "170",

"ldrscana" : "20.0",

"ldrscanr" : "53.4",

"ldrpulsr" : "273.0",

"ldrpulsd" : "9",

"ldrpulsw" : "8",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.22",

"ldrswatw" : "1455.88",

"ldrswato" : "12.49",

"ldrgeoid" : "GEOID12B",

"ldrcrs" : "NAD 1983 (2011) State Plane Vermont US Survey Feet"

},

"ldraccur" : {

"ldrchacc" : "0",

"rawnva" : "0.088",

"rawnvan" : "82"

},

"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" : "7",

"clasitem" : "Low noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground"

},

"lasclass" : {

"clascode" : "13",

"clasitem" : "Removed points for hydro enforcement"

},

"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 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.

An RMSEz = 0.045 meters was found using 82 RTK GPS validation points.

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.

Data cover the entire area specified for this project.

Data is backed up to cloud storage.