2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Cumberland and York Counties, Maine

In the fall of 2006, Sanborn Map Company was contracted by Camp Dresser McKee, Inc (CDM) to execute a LiDAR (Light Detection and Ranging) survey campaign in the state of Maine. LiDAR data in the form of 3-dimensional positions

of a dense set of masspoints was collected for the 584 sqaure miles of Cumberland and York Counties. This data was used in the development of the bare-earth-classified elevation point data sets. The Leica ALS-50 LiDAR system

was used to collect data for the whole 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.

Six airborne GPS (Global Positioning System) base stations were used in this project. A new point was set at the Portland Airport (501) The other base stations were set up at National Geodetic Survey (NGS) markers. NGS Monuments

901- PID: OC0229 and 801 - PID: OC0230 are located at the Biddeford Airport. The other existing NGS monuments used in the network are point 701 - PID: AJ2697, located on Bailey Island, point 702 - PID: OC0429, located at Fort

Constitution, and point 703 - PID: OC0478 located southeast of York Beach were tied to the other three points to create a GPS survey network. The coordinates of these stations were checked against each other with the three

dimensional GPS baseline created at the airborne support set up and determined to be within project specifications.

Leica ALS-50 LiDAR Scanner Parameters:

Pulse Rate: 50,000 hertz

Scan Frequency: 36 hertz

Scan Width (Half Angle): 18 degrees

Flying Height: 1,200 meters above ground level

Flying Speed: ~120 knots

The LIDAR derived data sets, including Bare Earth and a Gridded DEM support Camp Dresser and McKee's continued development of updated Digital Flood Insurance Rate Maps and flood insurance studies for coastal areas

located in Cumberland and York Counties, Maine. Acquisition is Tide restricted to +/- 3 hours from Low tide.(Source: FEMA Guidelines and Specs, Appendix N).

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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/geoid18/2479/supplemental/me2006_fema_cumberlandyork_footprint.KMZ

LiDAR points in LAS 1.0 format

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

of Camp Dresser McKee Inc., Sanborn Map Company, FEMA, 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=2479

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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 NSSDA is used to report the horizontal accuracy of the base map data used by FEMA to produce a FIRM. The NSSDA uses radial accuracy (Accuracy) to report the radius of a circle of uncertainty, such that the true or

theoretical location of a point falls within that circle 95 percent of the time. (Guidelines and Specifications Vol 1, p. 70)

; Quantitative Value: 1.0 meters, Test that produced the value: Value in meters. Project specifications require a horizontal accuracy of 1.0 meters. Data not tested but compiled to meet.

The LiDAR data was evaluated by Sanborn using a collection of 24 GPS surveyed checkpoints. The data set's consolidated vertical accuracy is 0.165 meters (0.54 feet) RMSEz.; Quantitative Value: 0.165 meters, Test that produced the value: RMSEz in meters for all points.

The NOAA Office for Coastal Management visually inspected the bounding boxes of each tile. The only void in the data set is a portion of tile 20071127_27801050.

Tests for logical consistency are performed by DFIRM tools topology verification software. The NOAA Office for Coastal Management checked the data set for logical consistency.