2018 USGS Lidar: Upper Middle Neck, VA

Products: This VA_UpperMiddleNeck_2018_D18 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 (2ppsm). Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The original data was developed based on a horizontal projection/datum of NAD83 (2011), Albers Equal Area, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to individual 1000 m x 1000 m tiles.

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 v1.3",

"ldrsens" : "ALS80",

"ldrmaxnr" : "5",

"ldrnps" : "0.5",

"ldrdens" : "4",

"ldranps" : "0.35",

"ldradens" : "8",

"ldrfltht" : "2650",

"ldrfltsp" : "150",

"ldrscana" : "26.5",

"ldrscanr" : "55",

"ldrpulsr" : "534",

"ldrpulsd" : "2.5",

"ldrpulsw" : "0.75",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.2",

"ldrswatw" : "1150",

"ldrswato" : "56",

"ldrgeoid" : "National Geodetic Survey (NGS) GEOID12B"

},

"ldraccur" : {

"ldrchacc" : "0.309",

"rawnva" : "0.102",

"rawnvan" : "107"

},

"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

The horizontal errors in lidar data are largely a function of the Global

Navigation Satellite System (GNSS) positional errors, the Inertial Measurement

Unit (IMU) angular errors, and the flying altitude. If the accuracy of the

GNSS/IMU solution is known for the specific POS system, using the flying

altitude of the project the expected horizontal errors in the LiDAR data can be

estimated. Following the formula in the ASPRS Positional Accuracy Standards for

Digital Geospatial Data (Edition 1, Version 1.0. - November, 2014), using the

specifications of the POS system used and 2651 m flying altitude above ground,

the estimated horizontal accuracy is RMSEr = 0.34 m.

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

The USGS values are as follows:

The number of Checkpoints tested for NVA : 145

The NVA RMSEz= 5.22 cm

The NVA Accuracy z at 95% confidence interval (RMSEz * 1.96) = 10.23 cm

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; 20171231.

Data is backed up to cloud storage.