2009 National Renewable Energy Laboratory/Boston Redevelopment Authority Topographic LiDAR: Boston, Massachusetts

The Alliance for Sustainable Energy, LLC contracted with Sanborn to provide LiDAR mapping services for the Boston area.

Utilizing multi-return systems, Light Detection and Ranging (LiDAR) data in the form of 3-dimensional positions of a dense

set of mass points was collected for approximately 90 square miles. All systems consist of geodetic GPS positioning,

orientation derived from high-end inertial sensors and high-accurate lasers. The sensor is attached to the aircraft's underside and emits rapid pulses of light that are used to determine distances between the plane and terrain below.

Specifically, the Leica ALS-50 LiDAR system was used to collect data for the survey campaign. The LiDAR system is calibrated by

conducting flight passes over a known ground surface before and after each LiDAR mission. During final data processing, the

calibration parameters are inserted into post-processing software.

Lidar Acquisition Parameters:

Instrument: Leica ALS50

Flight Altitude: near 1500m AGL

Airspeed: near 120 Knots

Scan Frequency: 46 Hertz

Pulse Rate: 74,400 Hertz

Scan Width Half Angle: 25 Degrees

Sidelap: 30 percent

This Lidar survey achieved a point spacing of 1.0 meter.

This LiDAR operation was designed to create a data sets that will establish an authoritative source for elevation information

for the city of Boston.

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

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2575/supplemental/ma2009_ase_boston_footprint.kmz

A Lidar Report from the vendor for this data set may be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2575/supplemental/ma2009_ase_boston_lidarreport.pdf

LiDAR points in LAZ format (ASPRS Classes 1,2,7,12)

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Any conclusions drawn from the analysis of this information are not the responsibility of Sanborn Map Company, the National Renewable Energy Laboratory,

the Boston Redevelopment Authority, the Alliance for Sustainable Energy LLC, 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=2575

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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.

Elevations are recorded in floating-point meters and the vertical datum is ellipsoidal (GEOID03).

Project specifications required a horizontal accuracy of 1.0 meter or greater in order to meet FEMA guidelines for Lidar-based DEMs.

Vertical testing of this data set does not meet NSSDA/ASPRS guidelines for vertical accuracy reporting. Until industry standard

vertical accuracy testing is conducted the accuracy cannot be assumed better than the project specification of 15cm RMSEz in bare

areas, 30cm RMSEz in vegetated areas. Please note that the vertical accuracy value in the Lidar Report found above in the

Supplemental_Information section above were collected by Sanborn for their own internal accuracy assessments.

; Quantitative Value: 0.15 meters, Test that produced the value: Root mean square Z error in bare areas. Units in meters.

Elevation data has been collected for all areas inside project boundaries. The data set was flown with a 30% sidelap between flightlines.

Data was reviewed by vendor to guarentee: 95% Artifact Removal, 98% Outlier Removal, 97% Vegetation Removal, 99% Building Removal.

Additionally, NOAA OCM reviewed each las tile's extent and statistics (including high/low elevations) to check for outliers, data voids,

blunders, etc. None were found by NOAA OCM.