2006 Federal Emergency Management Agency (FEMA) Topographic Lidar: Bristol and Plymouth Counties, Massachusetts

FEMA Contract No. EME-2003-CO-0340

FEMA Task Order T018

Sanborn Map Company furnished the collection and processing, and development of Lidar and contours using photogrammetry to support the FEMA mapping

requirements for a total of 142 square miles in coastal areas in Plymouth and Bristol Counties in Massachusetts. The 142 square miles includes the

communities of Westport, Dartmouth, New Bedford, Fairhaven, Mattapoisett, Marion, and Wareham. The project area was defined using a buffered shapefile

with limits along the coastline. The project area included a portion of both counties. All lidar data was acquired during November 2006 by Sanborn.

Orthophotography used to create 2D breaklines was produced in 2005 by MassGIS as part of its statewide orthophoto program. All lidar data that

was acquired was produced in accordance with FEMA specifications (Source: FEMA Guidelines and Specifications, Appendix N, Section N.1.2).

Lidar Acquisition Parametes:

Average Altitude: 1,200 Meters AGL

Airspeed: ~120 Knots

Scan Frequency: 36 Hertz

Scan Width Half Angle: 16 Degrees

Pulse Rate: 50000 Hertz

The data being distributed through the NOAA Digital Coast are Gridded Bare-Earth LAS files.

The LIDAR derived data sets, including the first and last returns, a Gridded DEM, TIN file, 2' contours in ESRI geodatbase format and masspoint and

Breakline files were developed to support Camp Dresser and McKee's continued development of updated Digital Flood Insurance Rate Maps and flood

insurance studies for coastal areas in Massachusetts. Contours are based on bare earth LIDAR and breaklines digitized from 2D orthophotography

(subsequently draped over the 3D LIDAR points) (Source: FEMA Guidelines and Specs, Appendix N). Coastal shoreline areas were set a 0.00 elevation to

cartographically represent contours.

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A complete description of this dataset is available in the project report submitted to FEMA Region 1 by CDM:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2602/supplemental/ma2006_fema_bristolplymouth.pdf

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2602/supplemental/ma2006_fema_bristolplymouth.KMZ

LiDAR points in LAZ format (ASPRS Class 2,7)

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Any conclusions drawn from the analysis of this information are not the responsibility of FEMA, Sanborn, CDM, MASSGIS, NOAA, the Office for Coastal Management

or its partners.

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=2602

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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. These data depict the

heights at the time of the survey and are only accurate for that time.

The lidar data was evaluated using a collection of 11 GPS surveyed checkpoints. The category classes of bare earth, low grass and urban were used.

For the Bristol checkpoints, the RMSEz is 14.7 centimeters. This area yielded much better results than the project requirement of 18.5 centimeters

RMSEz. The vertial accuracy of the source data meet or exceed vertical National Map Accuracy Standards for 2-foot contour mapping. Please set the

Project Report located in the supplemental information section above for more details.

; Quantitative Value: 0.294 meters, Test that produced the value:

This value reflects the data's tested Vertical Root Mean Squared Error (RMSEz) at 95% confidence interval (RMSEz @ 95% confidence = RMSEz x 1.9600)

as defined by the Federal NSSDA (National Spatial Standard for Data Accuracy). Units in meters.

Terrain data are derived datasets that aid automated hydrologic and hydraulic analyses, the flood hazard area boundary delineations, and quality control.

Sanborn used proprietary algorithms to remove features and artifacts in the first and last return data that did not reflect true ground elevations. New

aerial stereo photography was flown, and aerial triangulated to allow production of breakline ehnacement of the Bare earth DEM and to hydrologically

enforce contours and elevation data through the compilation of drainage breaklines.