Center for Geographic and Statistical Analysis

The Center for
Geographic and Statistical Analysis




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