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Core
Technical Expertise
Aerial
Photography
With over 200
years of corporate experience, Sewall and its southeast division
have provided clients with aerial photography services for such
applications as photogrammetric base mapping and orthophotography,
forest species identification and wetlands surveys, engineering
design, and utilities corridor mapping. The largest aerial photography
firm in New England, Sewall has flown missions for pulp and paper
companies, utilities, mapping and engineering firms, federal agencies,
and municipalities. Our southeast division, formerly Park Aerial
Surveys, has captured photography since the 1920s for mining, agriculture,
forestry, and utilities industries as well as federal and state
governments. To date, we have captured close to 3 million aerial
photographs covering New England and New York, the Southeast, the
Midwest, Alaska, and the Caribbean. We maintain archives of over
1.2 million photographs.
EXPERIENCED
PERSONNEL
Sewall photopilots
have decades of experience in flight planning, aerial photography,
and aerial survey quality control. Recognizing the time-sensitive
nature of aerial photography projects, we respond quickly to unpredictable
weather, narrow windows of opportunity, and tight project schedules.
Sewall owns and maintains a fleet of twin-engine aircraft, precision-calibrated
mapping cameras, and airborne GPS to aid in flightline navigation.
INERTIAL MEASUREMENT
UNIT (IMU) TECHNOLOGY
On some missions, Sewall
photographers use advanced inertial measurement technology to georeference
aerial photography quickly and directly. An integral attachment
to the aerial camera, the inertial measurement unit, or sensor,
is linked to the airborne GPS unit to provide both real-time and
post-processed measurements of the position and rotation of each
photograph. During the flight, the system collects and measures
the position of the camera perspective center and orientation angles
of each photograph at the exact time of exposure. Direct georeferencing
of aerial photography produces mapping that meets national standards
with little ground control and no aerial triangulation. Our clients
realize significant reductions in production time and cost as a
result.
QUALITY
PROCESSING
Depending
on the intended use of the photography, we expose black-and-white,
color, and color infrared films. At both Old Town and Louisville
facilities, Sewall operates a photographic laboratory, with advanced
black-and-white and color processors and copy cameras. We produce
a range of products, including contact prints and diapositives,
color and color infrared transparencies, translucent mylars, flight
indexes, photomosaics, and screened enlargements. To control data
quality, our technicians subject all photo products to rigorous
inspection during processing. In addition, we offer digital imaging
processing and photogrammetric-quality scanning services.
To
view a selection of aerial photographs from our archives, see Aerial
Photographs. To purchase aerial photography from the Sewall
archives, please fill out our Aerial Photography Order Form.
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