2004 Maryland Department of Natural Resources LiDAR: Anne Arundel, Charles, Howard and St. Mary's Counties

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.

Original contact information:

Contact Name: Ken Miller

Contact Org: Maryland Department of Natural Resources

Title: Chief. Watershed Information Services Division

Phone: 410-260-8751

Email: kenmiller@dnr.state.md.us

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.

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1. The Sanborn Map Company, Inc. (flight firm)

2. Computational Consulting Services, LLC (processing firm)

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

4. Dewberry and Davis (QA/QC firm)

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 Anne Arundel/Howard Counties and Charles/StMarys Counties, Maryland QA Reports may be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/27/supplemental/index.html

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the OCM or its partners.

This data set can be obtained online at the following URL: https://coast.noaa.gov/dataviewer;

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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 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.

A variety of specialized hardware and software platforms were used to collect, process and quality assess

these data. Typically, Intel machines running Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4.

There are four (4) attributes in the Bare Earth Mass Points files, representing the horizontal coordinates

(easting and northing) and vertical position observed and vertical assigned (see process description). Random inspections were made to

assure that each line in the file contained 4 values.

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: 0.143 meters, Test that produced the value:

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

information.

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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.