What is ortho-rectification?
Ortho-rectification is the process where aerial
photographs are registered to a map coordinate system and potential
measurement errors are removed.
Why is it different from simple aerial photographs?
Measurements from regular aerial photographs are
not consistent across the entire image. Ground terrain, the camera
lens and other factors makes measuring distances inaccurate. Ortho-rectifying
removes most of those errors
What is the process to rectify an image?
We ortho-rectify images using Erdas and Leica LPS 9.2
software. We calibrate the images to camera information, register
the images to ground control points, apply terrain models, tie the
images together and rectify. When an image has been rectified, it
is clipped and mosaiced with other rectified images. These images
are then made accessible in both Arcview and ArcInfo. The rectified
images can then be brought up with other layers such as parcel lines,
parcel numbers, hydrology, critical areas, contour lines, roads, etc.
What are ortho-photographs used for?
Ortho-photos are most often requested by landowners
who wish to see an aerial view of their property, usually with parcel
lines designated as in the example below.
Landowners use ortho-photos to locate features surrounding
their property such as orchards, streams, wetlands and other critical
areas, residential areas, and businesses. In addition to landowners,
engineering and surveying firms, construction companies, developers,
and independent planners request ortho-photos. On a daily basis, this
is our most frequently requested map product. Please refer to our products
and services for details on costs.
We currently have ortho-photography from 1992, 1994, 1996, 1998,
2002, 2005, 2006 and 2008 covering the inhabited areas of Yakima County along Interstate
82 and the major highways. We also have ortho-photography for the Yakima
Urban area flown in 2004 and 2008.
If you are interested in obtaining Ortho-Photos
contact us, we can
work with the Washington State Department of Transportation to provide
you with high quality, affordable ortho-photography.
Copyright (C) 2005 Yakima County