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James W. Sewall


Ortho of wooded peninsula Wetlands Covertype mapping

Natural Resource Mapping

For a wide variety of natural resource information needs, Sewall provides all required services, including project design, aerial photography, photo-interpretation, and production of final mapping products. We are experienced in acquiring appropriate imagery for projects ranging in size from several thousand to a million acres. We efficiently produce orthophotography from aerial imagery, and our seasoned photo-interpreters use softcopy stereo compilation systems or photogrammetry to interpret to client typing schemes.

Approximately 70 percent of our interpretation is of detailed forest cover types that are required for managing large tracts of forest land. The same skills and technologies are applied for interpretation and mapping of non-forest vegetation and land use. Although we are not heavily dependent on automated interpretation methods, we use them when they are cost-effective and appropriate to the project at hand. We assess forest damage--losses due to insect, disease, or weather--on wide areas with change detection methods using LANDSAT imagery, for example, and develop canopy height data from publicly available LiDAR data sets for use in forest inventory, and vegetation classification.

Sewall creates and/or enhances natural resource data sets at up to a state scale. We have adjusted cadastral data to fit deeds and orthophotos and built legacy hydrological data into complex linear-referenced geodatabase structures. We use our GIS analysis skills to assist clients in understanding land use or vegetation trends using sequential data sets and in modeling optimum siting.

Our worldwide client base is made up of managers of forest or other natural areas, including TIMOs, REITs, NGOs, the US Fish & Wildlife Service, state DNRs, and municipal watersheds.

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Covertype mapping services (PDF)

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