2017 Maryland Lidar: Anne Arundel County, MD

This metadata record describes the lidar point cloud for the 2017 Anne Arundel LiDAR project covering approximately 450 square miles in Anne Arundel County in Maryland. This dataset meets QL1 accuracy and point density requirements.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments, and hydrologic modeling. The point clouds are suitable for 1 foot contour generation. USGS LiDAR Base Specification 1.2, QL1.

USGA Base Specification 1.2, QL1 meeting 19.6 cm NVA

The digital data have been tested and their documentation carefully reviewed. However, the client and its representatives make no warranty or representation, either expressed or implied, with respect to the digital data and their documentation, their quality, performance, merchantability, or fitness for a particular purpose. The digital data are distributed on "as is" basis, and the user assumes all risk to their quality, the results obtained from their use, and the performance of the data. In no event will the client be liable for any direct, indirect, special, incidental or consequential damages resulting from and defect in the State of Maryland or in their documentation. This disclaimer of warranty is exclusive and in lieu of all others, oral or written, express or implied. No agent or employee is authorized to make any modification, extension, or addition to this warranty.

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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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.

Microsoft Windows 7; ESRI ArcCatalog 9.3.1.1850

Horizontal positional accuracy for the Anne Arundel LiDAR project is dependent upon the quality of the GPS/INS solution, sensor calibration and ground conditions at the time of data capture. The data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 1.0 meter RMSEx/RMSEy. Quantitative value: 1.0, Test that produced the valued: This value is computed by comparing ground control to a DEM derived from the classified LiDAR data and represents the RMSE of residuals on controls within the project area.

For the DEM data derived from the classified point cloud, the NVA and VVA were computed. The vertical accuracy was tested with independent survey check points located in various terrain types within the project area. These 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 block area. Specifications for this project require that the NVA be 19.6 cm or better @ 95 percent confidence level.

Quantitative value: 0.081m RMSE, or 0.16m NVA @ 95 percent Confidence Level 0.087m RMSE, or 0.14m VVA @ 95th Percentile,

Test that produced the value: The NVA was tested using 41 independent survey check points located in bare earth terrain types within the project area. The 41 independent check points contained all NVA points and were surveyed using static GPS base stations collecting point location for 20 minute intervals. Elevations were measured for the x,y,z location of each check point. Elevations interpolated from the DEM surface were then compared to the elevation values of the surveyed control. This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 10cm RMSEz Vertical Accuracy Class. Actual NVA accuracy was found to be RMSEz = 8.1cm, equating to +/- 16cm at 95% confidence level.

The VVA was tested using 31 independent survey check points located in various vegetation terrain types within the project area. The 31 independent check points were surveyed using static GPS base stations collecting point location for 20 minute intervals. Elevations were measured for the x,y,z location of each check point. Elevations interpolated from the DEM surface were then compared to the elevation values of the surveyed control. This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 10cm RMSEz Vertical Accuracy Class. Actual VVA accuracy was found to be +/- 14cm at the 95th percentile.

LiDAR data is collected for the project area. Post processing of the simultaneously acquired GPS/INS is performed and applied to the laser returns to output a point cloud in the specified project coordinate system and datums. The point cloud data is then subjected to automated classification routines to assign all points in the point cloud to ground, water, overlap and unclassified point classes. Anomalous laser returns that occur infrequently are removed entirely from the data set. Once clean bare earth points are established, all products are created. The products are then compared to the survey checkpoints. These accuracies must pass the NVA and VVA accuracy specifications.

LiDAR data is collected within the project area and processed. After all of the deliverables were created, the dataset was verified against control. Well-distributed control was collected for the project area.

Data is backed up to cloud storage.