Minnesota NRCS Slide Scaning Project
By Matthew Baltes – MN State GIS Coordinator
For the last decade, Minnesota NRCS employees have joined efforts and resources to scan over 1.2 million slides for conservation purposes and conducting certified wetland determinations. The scanned slides are historical Farm Service Agency aerial compliance imagery that spanned from 1979 to 2000, representing a period in time before the switch to digital imagery. This dataset is proving to be invaluable among NRCS employees, the State of MN, and future generations.
Imagery flown for the Farm Service Agency from 1979-2000 was stored on 35mm slides in the county service center for use in FSA compliance efforts. These slides also became useful to NRCS in their efforts in implementing conservation practices within the state. These slides were preserved quite well across the state in either the county service center or at the U of M Borchert Library. Though FSA’s need for the imagery diminished, NRCS uses were increasing. FSA eventually released the slides to NRCS control. The need to preserve and also to make this dataset readily available was recognized by leadership and staff, and the effort began.
NRCS purchased its first slide scanners in 2002 (est.) to begin the daunting task of scanning thousands of slides per county. The scanning was done by many employees and disciplines including Earth Team Volunteers, Engineering Staff, Administrative Assistants, GIS Specialists, Biologists, the Center of Excellence and temp workers. In 2004 the Area GIS Specialists adopted the effort, making the process more consistent and efficient across the state. They also devised a system for storage and backup to ensure loss of data would be nearly impossible. The amount of data piling up proved to be a challenge. Take this estimation for example:
Todd County 979 Square Miles (closest to mean average size)
979 sqmi * 20 years of slides = 19,580 .jpg images
Average image uses nearly 3 MB of hard drive space
19,580 * 3MB = 58,740 MB or 57.4 GB
When the project started, county service center servers had less than 90 GB of usable space, most of which was already in use. There was no place to store this dataset locally. The purchase of shared portable hard drives in the county offices and NAS servers in the area offices have allowed for the storage of this dataset and access to everyone in the office. Slides are also linked into ArcGIS maps through a hot linking tool, allowing instant access by the click of a spatial location on the screen.
Recently, NRCS provided a copy of this preliminary dataset to the U of M Borchert Library, which will make it available for public use. Most of the completed counties have been delivered to the library; the rest will follow as this effort comes to an end with the scanning of the few remaining slides. Thank you to everyone involved in this effort and to NRCS leadership for appropriating the resources to complete this project. This will be a valuable resource for MN in the years to come.