2020 USGS Lidar: Northern Shenandoah, VA

Products: This VA_NorthernShenandoah_2020_D20 project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at an aggregate nominal pulse spacing (ANPS) of 0.71 meters (4ppsm). Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 2.1. The data was developed based on a horizontal projection/datum of NAD83 (2011), UTM17N, meters and vertical datum of NAVD88 (GEOID18), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to individual 1500 m x 1500 m tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 1500 m x 1500 m schema.

Data were subsequently reprocessed to Entwine Point Tile (EPT) format in web mercator projection with vertical meters. The EPT form of the data is used by the NOAA Digital Coast Data Access Viewer, which this metadata record is supporting. Additional processing steps may have been done by the Data Access Viewer and will be recorded in the lineage section.

This high resolution lidar data will support the United States Geological Survey (USGS) initiatives.

USGS Contract No. G17PC00015 CONTRACTOR: Fugro Geospatial, Inc. SUBCONTRACTOR: Terrasurv, Inc. Ground control and checkpoints collected by Terrasurv, Inc. All processing was completed by the prime contractor.

Point Cloud File Type = LAS v1.4

Point Record Format 6, 7, 8, 9, or 10 including "File Source ID"

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "USGS-NGP Base Lidar Specification v2.1",

"ldrsens" : "Leica ALS80",

"ldrmaxnr" : "6",

"ldrnps" : "0.71",

"ldrdens" : "2",

"ldranps" : "0.71",

"ldradens" : "2",

"ldrfltht" : "2330",

"ldrfltsp" : "150",

"ldrscana" : "30.8",

"ldrscanr" : "37.8",

"ldrpulsr" : "241",

"ldrpulsd" : "2.5",

"ldrpulsw" : "0.75",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.26",

"ldrswatw" : "1290",

"ldrswato" : "18",

"ldrgeoid" : "National Geodetic Survey (NGS) GEOID18"

},

"ldraccur" : {

"ldrchacc" : "0",

"rawnva" : "0",

"rawnvan" : "0"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "There were no withheld points identified in this project. All points were used in the classification.",

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

"lasintr" : "16 bit",

"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" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

},

"lasclass" : {

"clascode" : "20",

"clasitem" : "Ignored Ground (breakline proximity)"

}

}}

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.

POSGNS 5.2; POSPac 6.2; RiProcess 1.8.3; RiWorld 5.0.2; RiAnalyze 6.2; RiServer 1.99.5; Microstation CONNECT 10.00.00.25; TerraScan 017.039 and 016.013; TerraModeler 016.001; Lasedit 1.35.07; GeoCue 2014.1.21.5; ArcMap 10.3; Global Mapper 17.1.2; ERDAS Imagine 2016; PhotoShop CS8; Fugro proprietary software; Windows 7 64-bit Operating System

\\server\directory path\*.las

\\server\directory path\*.las

\\server\directory path\*.img

\\server\directory path\*.gdb

\\server\directory path\*.tif/tfw

1440 GB

This data was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 21.2 (cm) RMSEx/RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 51.9 cm at 95% confidence level.

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

The Non-Vegetated Vertical Accuracy (NVA) of the Lidar Point Cloud data was calculated against TINs derived from the final calibrated and controlled swath data.

Measured values: 3.1 cm RMSEz NVA using 85 checkpoints, equivalent to 6.3 cm at 95% confidence level.

Vegetated Vertical Accuracy (VVA) measured 11.8 cm at 95% confidence level.

A complete iteration of processing (GPS/IMU Processing, Raw Lidar Data Processing, and Verification of Coverage and Data Quality) was performed to ensure that the acquired data was complete, uncorrupted, and that the entire project area had been covered without gaps between flight lines. No void areas or missing data exist. The raw point cloud is of good quality and data passes Vertical Accuracy requirements.

The Classified Point Cloud data files include all data points collected except the ones from Cross ties and Calibration lines. The points that have been removed or excluded are the points fall outside the project delivery boundary. Points are classified. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The classified point cloud is of good quality and data passes Vertical Accuracy requirements.

The Intensity Image files cover the entire project delivery boundary. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The Intensity Image product is of good quality.

The Hydro Breaklines cover the entire project delivery boundary and extend beyond the boundary in a few locations. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The Hydro Breakline product is of good quality.

The DEM raster files cover the entire project delivery boundary. The pixels that fall outside the project delivery boundary are set to Void with a unique “NODATA” value. The value is identified in the file headers. There are no void pixels inside the project boundary. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The bare earth surface is of good quality and passes Vertical Accuracy requirements.

Compliance with the accuracy standard was ensured by the collection of ground control and the establishment of GPS base stations in the project area. The following checks were performed: 1) The lidar data accuracy was validated by performing a full boresight adjustment and then checking it against the ground control prior to generating a digital terrain model (DTM) or other products. 2) Lidar elevation data was validated through an inspection of edge matching and visual inspection for quality (artifact removal). The following software was used for the validation: 1) RiProcess 1.8.3, RiWorld 5.0.2, RiAnalyze 6.2, RiServer 1.99.5; and 2) Fugro proprietary software; 20200520.

Data is backed up to cloud storage.