2002 Maryland Department of Natural Resources LiDAR: Worcester County

Light Detection and Ranging (LiDAR) is a method of locating objects on the ground using aerial-borne equipment. It is similar to RADAR or SONAR in that the two-way travel time of an energy beam reflected off an object is precisely measured, but this technology uses laser light instead of radio or sound waves. This technology has proven very useful in remote sensing of the earth. It can be used for determining elevations of both the earth's surface and items (natural and man-made) on the surface. Analysis of LiDAR data is used in detailed modeling of the earth's surface for drainage and floodplain studies, determining how a new structure will affect views from various locations, shoreline erosion studies, and other reasons. This data set contains only the bare earth mass points. Bare earth points represent ground features. Features that are above ground, such as buildings, bridges, tree tops, etc., have been eliminated. Mass points may appear to have "holes" with no elevation values in areas where the surface could not be determined, such as very dense forests or urban areas.

The LiDAR-derived data were collected by the Maryland Department of Natural Resources in support of shore erosion studies along the shorelines of the Chesapeake Bay. It also supports the Federal Emergency Management Agency's specifications for mapping floodplains. These efforts required detailed elevation data and models, such as those available from LiDAR sensing. The data have also been made available to aid in other projects that require detailed surface, vegetation and/or structure elevations.

10424

1. Airborne 1 (flight firm)

2. Computational Consulting Services, LLC (processing firm)

3. Spatial Systems Associates, Inc. (post-processing firm)

4. Dewberry & Davis (QA/QC firm)

5. Maryland Department of Natural Resources

These data are part of a suite of spatial data products generated using the LIDAR technology. First and Last returns are generated. From these data, Bare-Earth Mass Points that represent the earths surface are produced. A gridded Digital Elevation Model (DEM) is produced from the Bare Earth Mass Points. Imagery is also created that represents the intensity of the LIDAR return; it is a 1-meter resolution product that resembles a panchromatic Digital Orthophoto Quad (DOQ).

The Worcester County, Maryland LiDAR Review-2005 Report may be viewed at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/15/supplemental/index.html

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

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer;

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 NOAA and Department of Natural Resources makes no warranty, expressed or implied, as to the

use or appropriateness of Spatial Data, and there are no warranties of merchantability or fitness for a particular purpose or use.

The information contained in Spatial Data is from publicly available sources, but no representation is made as to the accuracy or

completeness of Spatial Data. The Department of Natural Resources shall not be subject to liability for human error, error due to

software conversion, defect, or failure of machines, or any material used in the connection with the machines, including tapes, disks,

CD-ROMs or DVD-ROMs and energy. The Department of Natural Resources shall not be liable for any lost profits, consequential damages,

or claims against the Department of Natural Resources by third parties. The liability of the Department of Natural Resources for

damage regardless of the form of the action shall not exceed any distribution fees that may have been paid in obtaining Spatial Data.

None available

The horizontal coordinate values were designed to meet NSSDA accuracy for data at

1:2400 scale.

The RMSE value of 14.3 cm at the 95% confidence level was determined by an independent

accuracy assessment conducted by Dewberry LLC according to the contract specifications. These specifications followed FEMA

Appendix A guidelines regarding assessing vertical accuracy. For data accurate to within 18.5 cm RMSE, the guidelines

recommended a minimum of 20 independent check points be located in each of 5 different land cover categories: Grass/Ground,

High Grass/Crops, Brush/Low Trees, Forest, and Urban/Pavement. A total of 125 points were used for the assessments. These

points were surveyed by a licensed land surveyor and provided a positional location and elevation with an accuracy that

exceeded the predicted accuracy of the LIDAR data. The entire accuracy reports can be found at

http://dnrweb.dnr.state.md.us/gis/data/lidar.

; Quantitative Value: 14.3 meters, Test that produced the value:

The RMSE value is 14.3 cm. See the Vertical Positional Accuracy Report section

for more information.

Spatial Systems Associates performed various inspections of the data to ensure: that each file contained the points

located within that tile; that tiles were completely filled; that the point density per tile was within expected ranges, and that

the tiles were correctly named.

Computational Consulting Services, the LIDAR processing vendor used proprietary algorithms to remove

features and artifacts in the First and Last Return data that did not reflect true ground elevation. Subsequent quality assurance

testing by Dewberry determined that the data met FEMA and MD DNR specifications for both vertical accuracy and other consistencies

with accepted standards. The QA report can be accessed at <http://dnrweb.dnr.state.md.us/gis/data/lidar>.