2018 Maryland Lidar: Ellicott City, MD

Products: This project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at an aggregate nominal pulse spacing (ANPS) of 0.35 meters (8ppsm). 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 a horizontal projection/datum of NAD83 (2011), Maryland State Plane, feet and vertical datum of NAVD88 (GEOID12B), feet. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to individual 4000 ft x 6000 ft tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 4000 ft x 6000 ft schema. The USGS reference is VA_UpperMiddleNeck_2018_D18.

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" : "0.053",

"rawnva" : "0.027",

"rawnvan" : "19"

},

"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)"

},

"lasclass" : {

"clascode" : "21",

"clasitem" : "Snow (where reliable identifiable)"

},

"lasclass" : {

"clascode" : "22",

"clasitem" : "Temporal Exlusion (typically non-favored data in intertidal zones)"

}

}}

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.

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.

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. The required accuracy (ACCZ) is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSEZ of 10 cm in the “open terrain” and/or “Urban” land cover categories. This is a required accuracy. The raw swath point cloud data met the required accuracy levels before point cloud classification and derivative product generation. The calculated NVA value using 19 NVA checkpoints was 2.7 cm RMSE.

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 tape and to cloud storage.