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