2024 USGS Lidar DEM: Maryland 4 County (Baltimore, Baltimore City, Carroll, Garrett, St. Mary's)

Products: These are the raster digital elevation model (DEM) data for the Maryland 4 County project level delivery, as part of the required deliverables for the USGS Maryland 4 county project.

Geographic Extent: This dataset consists of two blocks of data, covering approximately 2250 square miles in four counties (including Baltimore City) in Maryland.

MD_4County_1 (Work Unit 301118) - 665.5 square miles in Garrett County

MD_4County_2 (Work Unit 301119) - 1584.5 square miles in Baltimore, Baltimore City, Carroll, and St. Mary's counties.

Dataset Description: 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 2024 Rev A. The data was developed based on a coordinate reference system NAD83(2011) / UTM zones 17N (EPSG: 6346) and 18N (EPSG: 6347), meters; Geoid 18. Lidar data was delivered as processed LAS 1.4 files, formatted to individual 1000 m x 1000 m tiles, and as tiled derived bare earth DEMs; all tiled to the same 1000 m x 1000 m schema, intensity images, breaklines, swath separation images and maximum height surface rasters.

Ground Conditions: Lidar was collected in Winter of 2024, under cloud, fog, and snow free conditions, with no unusual flooding or inundation.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

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

USGS Contract No. 140G0221D0010 CONTRACTOR: Fugro Geospatial, Inc. SUBCONTRACTOR: Terrasurv, Inc. Ground control and checkpoints collected by Terrasurv, Inc. All processing was completed by the prime contractor.

DEM Raster File Type = GeoTIFF

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 0.5 meters

Interpolation or Resampling Technique = Triangulated Irregular Network (TIN)

Network Required Vertical Accuracy = 10 cm NVA

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners.

MD_4County_2 (Work Unit 301119) - 1584.5 square miles in Baltimore, Baltimore City, Carroll, and St. Mary's counties.

MD_4County_1 (Work Unit 301118) - 665.5 square miles in Garrett County

To the extent possible under law, the U.S. Government has waived all copyright and related or neighboring rights to this dataset.

Data is available online for bulk and 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.

This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data, Edition 2 (2023) for a 18.9 cm RMSEh horizontal positional accuracy class.

This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data, Edition 2 (2023) for a 10 cm RMSEV Vertical Accuracy Class.

USGS Determined DEM Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 3.55 cm RMSE

Vegetated Vertical Accuracy (VVA) = 11.88 cm at 95th Percentile

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 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.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.