)
figure 1:click on image
)
)
figure 3:click on image
For 2005, 44 counties and at least 85 municipalities around the state acquired orthophotography (see figure 1).
As technology improves, processing costs fall and the marketplace opens up with new and improved products. While the majority of existing ortho imagery in the state is black-and-white, a significant amount of color imagery has been acquired this year (see figure 2). Lower production costs are also making high resolution imagery more affordable. In the past, it was unusual to find counties acquiring 12-inch resolution imagery, whereas now it's fairly common, even in some relatively rural areas. In 2005, eight counties obtained 6-inch imagery (see figure 3).
For status on the availability of the 2005 digital orthos, contact the respective county land information office.
Municipalities are active
At least 85 municipalities obtained orthophotography in 2005 as well. In most cases, cities and
villages acquired 6-inch resolution imagery in conjunction with a lower resolution (12-inch
or 18-inch) countywide project. One city, Fond du Lac, acquired 3-inch color imagery in the spring
of 2005.
Regional consortiums
In the northeast corner of the state,
the East Central RPC, the
North Central RPC, and the
Bay-Lake RPC pulled together counties in
their respective regions to coordinate a large ortho project. A similar consortia formed for 10 counties in the
southwest part of the state. In the Milwaukee area, the
Southeast Wisconsin RPC (SEWRPC) led the
initiative to acquire imagery on behalf of their member counties.
The role of the consortium in the three regions varied, but in all cases, cost savings were the most tangible result. Less noticeable, but equally as important, was the peer support that occurs when working together.
In the works
The Mississippi River RPC (MRRPC) is taking the lead on organizing a new orthophoto consortium.
The goal is to pull together up to 14 counties in northwest Wisconsin for spring 2006 ortho imagery.
The current proposal calls for 1-foot orthos to be acquired for each participating county, with an
option for LiDAR acquisition as well. Municipalities would also have the option to partner with
the counties for 6-inch imagery.
Background on digital orthophotos
A digital orthophoto is an electronically scanned aerial photograph that has been processed to
remove image displacements due to camera tilt and differences in terrain relief. Orthophotos are
useful because they combine the image characteristics of an aerial photograph with the geometric
qualities of a map.
Orthophotos are most commonly described by their resolution. Resolution refers to the linear ground distance represented by a single pixel in the digital image. For example, in a one-meter resolution orthophoto, each pixel represents a one-meter by one-meter square cell on the ground. With higher resolution, more ground detail will be visible.
History
As a technology development, digital orthophotos began to appear in the late 1980's. The concept
of a National Digital Orthophoto Program (NDOP)
was proposed in 1990 by the U.S. Dept. of Agriculture-Natural Resources Conservation Service
(USDA-NRCS), USDA-Farm Services Agency (USDA-FSA), and the
US Geological Survey (USGS). Technical
specifications (quarter-quadrangle format, black & white images, one meter resolution) were
soon established, and the NDOP began producing digital orthophotos in 1993 using
National Aerial Photography Program (NAPP)
imagery. The NDOP facilitated virtual nationwide coverage of the lower 48 states by 2002.