2004 ENSR Bare Earth Topographic Lidar: Hampden County, Massachusetts

Spectrum Mapping was tasked by ENSR International (now a subsidiary of AECOM Technology Corporation) to collect LIDAR data and digital

ortho imagery to generate breaklines and a bare earth DEM to support 2-foot contour intervals in accordance with FEMA Appendix A.

The project area for Connecticut River floodplain was approximately 143 square miles in Hampden County, Massachusetts. The

Spectrum aircraft was equipped with the RAMS system, including a 26 Khz Laser, an inertial measurement unit (IMU), and a dual

frequency GPS receiver and antenna. The RAMS sensor system also includes a RAMS 4K X 4K color digital camera mounted to the

LIDAR unit.

The purpose of this project was to collect LIDAR data and digital ortho imagery to generate breaklines and a bare earth DEM to

support 2-foot contour intervals in ccordance with FEMA Appendix A.

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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/geoid18/2577/supplemental/ma2004_ensr_hampden_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/geoid18/2577/supplemental/ma2004_ensr_hampden_projectreport.pdf

LiDAR points in LAZ format (ASPRS Class 2)

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Any conclusions drawn from the analysis of this information are not the responsibility of

ENSR International (AECOM Technology Corporation), Spectrum Mapping, 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=2577

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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 (GEOID99).

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

Green International Affiliates, Inc collected the 48 control points used below for the RMSE of the project areas. The RMSE below is

combined for the Massachusetts and Connecticut project areas. The final RMSEz is 14.7 centimeters (.483 feet). This exceeds the FEMA

Guidelines and Specifications for Flood Hazard Mapping.

; Quantitative Value: 0.147 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. As

part of the field QC process, data voids caused by operational errors are re-collected if required. Spectrum Mapping found no data voids in this

project.

Spectrum Mapping performs rigorous quality assurance program insures that the final data products meet all requirements prior to delivery

to the customer. Quality Assurance / Quality Control is embedded into the overall data acquisition and processing steps. Quality

assurance is inherent in developing the project plan, acquisition, verifying data and processing, and assuring that the final products

meet all FEMA requirements in accordance with the contract. Spectrum Mapping's quality assurance procedures follow the "FEMA Guidelines and

Specifications for Flood Hazard Mapping Partners, Appendix A: Guidance for Aerial Mapping and Surveying" for use of LIDAR mapping technology.