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Core
Technical Expertise
Photogrammetric
Mapping
With
production facilities in Old Town and Kentucky, Sewall is one of
the largest photogrammetric mapping firms in the country. We produce
accurate planimetric and topographic maps from aerial photography
to meet the diverse needs of municipalities, state and federal governments,
engineering firms, and utility companies. Using the most advanced
photogrammetric technology, Sewall personnel have assisted clients
on applications ranging from site-specific engineering-design projects
to pipeline corridor mapping and the mapping of entire towns for
municipal GIS.
DATA
CAPTURE
Sewall technicians
perform all data capture digitally on first-order analytical and
softcopy stereoplotters to produce maps in both hard copy and digital
formats. Our certified photogrammetrists rectify the aerial photography
and tie the mapping to a specified coordinate system, producing
two- and three-dimensional views of the terrain. Using these models,
we client-customize the capture of such planimetric features as
roads, utilities, lakes, buildings, and "street furniture," providing
attributes for database coverages as required. Known for aggressive
technique, our photogrammetrists capture all unidentifiable features
and store them for future reference. To produce topographic mapping,
we capture solid-line contours and digital terrain models at client-specified
intervals. For immediate database integration, we provide base map
files in a number of industry-standard formats. We are ready to
provide on-site training in the installation and use of all map
products and software on client systems.
ADVANCED
DIGITAL IMAGING
Using high-resolution
scans of aerial photography, our photogrammetrists develop orthophotos
as a base for parcel mapping, community planning, and map updates.
Sewall also produces digital terrain models from aerial photography
or existing contour information.
QUALITY
ASSURANCE
Sewall staff
exercise tight quality control throughout a photogrammetry project,
checking for data entry errors and specifications compliance. In
addition, we prepare and review check data and visually compare
sections of on-screen information with the aerial photographs. On
larger projects, we recommend conducting a pilot project to test
methodologies and establish successful procedures. Our personnel
work with clients to select a small representative area for prototype
mapping. In the prototype, we develop checkplots to help determine
the final mapping symbology and deliver corresponding digital map
data for client review. This information enables both client and
vendor to identify and handle project issues on a manageable scale
and to refine the project schedule. As a result, we assure clients
timely delivery of mapping that sets standards for quality and longevity.
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