The St. Louis County (Minnesota) Land Department manages approximately 900,000 acres of tax-forfeit land dispersed throughout the County's 4.5+ million acres. The principal (most-used, costliest to develop, largest data volume, greatest complexity) theme layer in our GIS is that which contains the 50,000+ polygons that describe the land surface features of this acreage. We've named this our COVER layer. Serving in its maintenance, the 150+ widely scattered, COVER-altering events (logging, forest fires, tree plantings, etc.) that occur annually on our lands are captured, on an ongoing basis, economically (a 1994 average of Å$15/event-area) on 35 mm vertical aerial photography using a 50 mm lens (minimized radial displacement) and CIR film (enhanced atmospheric penetration and vegetative information). The multitudinous slides so collected are annotated and stored in an efficient cataloging system to assure rapid access. Slides are rear-projected, scaled, and registered (utilizing a device called a Dendropolyplotter) onto current COVER maps, upon which are drafted pen and ink update polygons that reflect the imaged changes. These polygons are digitized and inserted (with some automated editing) into the original COVER layer, which then undergoes further manual editing (each update polygon will seriously alter up to several dozen of the original polygons), plus standard cleaning. Our COVER layer is thus maintained "current" to within one to six months of ground events.
Steve Opseth
St. Louis County Land Department
Room 607, Government Services Center
320 West 2nd St.
Duluth, MN 55802-1495
Telephone: 218-726-2606
Fax: 218-726-2600
Email: