In Wisconsin, the federal government and state and local agencies produce digital orthophotos (DOPS) for use in various mapping programs and projects. In addition to these ongoing activities, public and private organizations and businesses increasingly utilize digital orthos in special projects and historical studies.
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Federal Production
The U.S. Geological Survey (USGS), in partnership with three U.S. Department of Agriculture entities -- the Farm Service Agency (FSA), the Natural Resources Conservation Service (NRCS), and the U.S. Forest Service (USFS) -- has been creating digital orthophotos (DOPs or orthos) since the National Digital Orthophoto Program (NDOP) was initiated in 1990.
The goal of the NDOP is to have complete ortho coverage of the 50 states and Puerto Rico, to update the coverage periodically (every 5 years for regions of rapid land use change, every 10 years elsewhere), and to ensure public availability.
The orthophotos are created primarily from National Aerial Photography Program (NAPP) imagery, which is acquired at a nominal scale of 1:40,000 and a resolution of 1-meter. Each orthophoto is centered on a quadrant of a U.S.G.S. 7.5-minute quadrangle map, resulting in a digital ortho quarter-quad, or DOQQ. Orthophotos are also available at the extent of full quadrangles (DOQs) through the mosaicing of the four DOQQs.
Complete DOQQ coverage of the contiguous United States is expected by 2004. Many states already have complete coverage --- and some of these states rely almost exclusvely on federally produced DOQQs, which certainly simplifies the ortho selection step.
Many areas of Wisconsin, on the other hand, have had incomplete DOQQ coverage until recently. Wisconsin has had a strong state land information program, and many counties have created their own ortho coverages since the mid-1990s. As a result, DOQQ production was somewhat "de-prioritized" for these counties. In some of these cases, DOQQ production is now being accomplished through cost-sharing the re-sampling and re-tiling of locally-funded DOPS to DOQQ format. For example, 2-foot resolution DOPs registered to a county coordinate system, with each image covering 3 X 3 miles, can be resamples and reprojected to mimic DOQQs made directly from NAPP photos.
More information on the production of orthos can be found at the USGS's Digital Orthophoto Quadrangles page. Or to see the current status of DOQQ production in Wisconsin, go to the USGS's Wisconsin DOQQ Status page.
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State and Local Government Production
Wisconsin has been on the forefront of land information modernization since the 1980's. The Wisconsin Land Information Program (WLIP), established in 1990, coordinates and supports land records modernization by state and local governments. WLIP is a voluntary, cooperative effort among state, county, and municipal governments that is overseen by the Wisconsin Land Information Board. In addition to coordinating land records modernization efforts, WLIP provides technical assistance and grants to local governments.
At the state level, Wisconsin agencies have not typically been producers of orthoimagery over large areas. A few state agencies commonly use orthoimagery and may acquire site-specific orthophotography or use in-house software to orthorectify existing aerial photos. Up to this point, this limited production and expansive archiving is for internal agency uses and has not provided significant outlets to the public.
The Wisconsin Department of Transportation produces, for its internal use, orthophotos for use in construction and maintenance projects. The Department of Natural Resources may also, on a project basis, orthorectify site-specific imagery -- the most current of which it maintains in an archive for its internal use.
Many Wisconsin counties and municipalities have invested in new aerial photography and orthophoto production (independent of the USGS NDOP program) since the mid-1990's. Because of the the costs, technical demands, and time required, various local governments have often worked together -- through existing regional planning commissions or other consortiums -- to obtain the imagery and resources needed to create orthophoto coverages. Both public agencies and privately contracted companies have generally participated in the projects.
Rather than using quarter-quadrangles as the coverage unit, most locally-produced orthos are "township-based". That is, the coverage unit is based on the Public Land Survey System, such as a quarter township of 3 X 3 sections. Just over half of Wisconsin's 72 counties have completed township-based ortho coverage. Most of this work was initially done in the mid- to late-1990s. Just over a dozen counties have second-generation production already completed or in progress. As one might expect, more densely populated counties have complete first-generation coverage, and have proceeded to second-generation production. Orthofinder's Selection module presents a dynamic, updated view of of this increasingly complex picture. It also compares the features of township- and municipal-based orthos with the DOQQs
A recent illustration of orthophoto production by local governments has been Dane County's "Fly Dane" project. Various units of government (county, city, village, and town) have collaborated with Ayres Associates (which had previously produced DOPs for Dane County in 1995) to create orthos from aerial photos acquired in 2000. More...
Some other examples of projects to produce orthophotos are listed below.
- The Southeast Wisconsin Regional Planning Commission (SEWRPC) and East Central Wisconsin Regional Planning Commission have recently collaborated on a project to acquire new aerial photos and produce orthos. Previously (in the mid-1990's), a group of seven southwestern counties working on land records modernization formed the Southwestern Wisconsin Digital Orthophotography Consortium to obtain DOPs for use as base maps. In both cases, the consortiums contracted with Ayres Associates to acquire the aerial photos and produce the DOPs.
- Wisconsin cities and villages have also obtained orthophotos for various projects. For example, the City of Berlin recently obtained DOPs for use in mapping a nine-square mile area in the city. Similarly, the Village of Arlington purchased new DOPs as part of a project to map an area of approximately 180 acres.
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Historical and Project-Based Site-Specific Orthophoto Production
The federal, state, and local programs described above usually involve the systematic production of large numbers of orthophotos over a large area --- for example, a county or region. The programs are frequently ongoing, such as the USGS DOQQ program, or cyclical. For example, the local and regional DOP projects are often part of a long-term plan for regular DOP updates that include periodically re-photographing the area.
Apart from these ongoing public programs, DOPs are also produced for historical or site-specific projects, which focus on a more limited area and a particular purpose. While these projects can sometimes make use of DOPS produced from the ongoing programs just cited, they often rely on other sources. These can include creating DOPs from new aerial photos (taken specifically for the project) or producing orthophotos from historical aerial photos. The latter use is often especially important for historical studies and change analyses.
In recent years, relatively inexpensive desktop software has been developed that creates high-quality DOPs from scanned aerial photography. As a result, historical and site-specific orthophotos have become easier and less expensive to produce. At the same time, GIS has become widely utilized in land use and environment analysis --- and desktop DOP software has been used to integrate DOPs into GIS projects. As a result, "site-specific" orthophotos have been increasingly utilized as data layers for geospatial studies.
Some examples of projects and historical studies utilizing DOPs are described below.
- Professor Frank Scarpace, at the University of Wisconsin-Madison's Environmental Remote Sensing Center (ERSC) has developed software called OrthoMapper that easily converts historical photos into DOPs. Faculty, staff, and students have utilized OrthoMapper for a number of projects. A recent project has had a group from ERSC assisting in planning future design options for the University Ridge Golf Course in western Dane County. Part of the project has involved creating orthophotos from historical aerial imagery. ERSC has also utilized DOPS produced from historical imagery to study the effects of shoreline erosion (bluff face recession) along Lake Michigan and change detection among lakes in northern Wisconsin.
- ERSC and the UW-Madison Division of Facilities Planning and Management recently produced a Campus Image Map that was created from a mosaic ortho-rectified images. The images were produced from 79 individual aerial photos taken in May, 1999.
- An engineering company (Patrick Engineering) involved in restoration work at Taliesen, the historic Frank Lloyd Wright home and school near Spring Green, has produced orthophotos for use in the project.
- As noted above, the Wisconsin Department of Transportation has utilized site-specific orthophotos for construction and maintenance projects --- including road and interchange planning and construction.