Garrett County, MD 2015 LiDAR

The Garrett County, MD 2015 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 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LIDAR Specification, Version 1. The data was developed based on a horizontal projection/datum of UTM Zone 17, NAD83 (2011), meters and vertical datum of NAVD1988 (GEOID12A), meters. LiDAR data was delivered in RAW flight line swath format, processed to create Classified LAS 1.4 Files formatted to 6 individual 1829 meter X 1219 meter tiles for the pilot (948 individual 1829 meter X 1219 meter tiles for the entire project area).

Geographic Extent: Garrett County, MD, covering approximately 739 square miles.

Ground Conditions: LiDAR was collected in spring of 2015, 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, Quantum Spatial established a total of 87 Land Cover control points that were used to calibrate the LIDAR to known ground locations established throughout the Garrett County, MD project area (20 calibration control points).

Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create Intensity Images, Breaklines and Raster DEM.

The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 1 meter cell size.

These raw lidar point cloud data were used to create classified lidar LAS files, intensity images, 3D breaklines and hydro-flattened DEMs as necessary.

USGS Contract: G10PC00026 Task Order Number: G15PD00051

CONTRACTOR: Quantum Spatial

Lidar data were acquired and calibrated by Quantum Spatial.

No classification scheme was described in the original metadata. Based on the era and origin (USGS) of the data, and an examination of the point cloud compared to imagery, the classification scheme is believed to mostly follow that used by the 3DEP program. Classes are:

1 = undefined

2 = ground

7 = low noise

8 = model key point

9 = water

10 = ignored ground near breakline

17 = bridge deck

18 = 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 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.

MicroStation Version 8; TerraScan Version 15; TerraModeler Version 15; GeoCue Version 2014.1.21.1; ESRI ArcGIS 10.2; Global Mapper 16; Leica Cloud Pro 1.2; Windows 7 Operating System

\\psihq_nx3200\Projects\25442_GarrettCountyMD_USGS\ 1 TB and

\\Matrix\LIDAR\25442_Garret_Co_MD\ 1.18 TB

The specifications require that only Nonvegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The vertical accuracy was tested with 50 independent survey located in open terrain. These check points (check points) were not used in the calibration or post processing of the lidar point cloud data. The survey check points were distributed throughout the project. Specifications for this project require that the NVA be 25 cm or better AccuracyZ at 95 percent confidence level.Qualitative value:0.070, Test that produced the value: The NVA was tested using 50 independent surveys located in open terrain. The survey check points were distributed throughout the project area. The 50 independent check points were surveyed using the closed level loop technique. Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control. The RMSE was computed to be 0.036 meters. AccuracyZ has been tested to meet 19.6 cm Nonvegetated Vertical Accuracy at 95 percent confidence level using (RMSEz * 1.9600) as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

These raw 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 Nonvegetated Vertical Accuracy specifications.

Data cover the entire area specified for this project.