Point of Beginning - October 2009 - (Page 36)

program provided a better orthorectification solution as well as a means to meet Ohio’s other geospatial needs. Data Matters Accurate imagery and elevation data serve as the backbone for development of additional data sets maintained and accessed by government decision makers and the public. Before OSIP began, the majority of Ohio counties were using older aerial imagery as a point of beginning for myriad projects. But resolution, age and accuracy varied from county to county. The DEMs used to orthorectify the imagery also varied. Twenty-seven Ohio counties had created DEMs using photogrammetric processes. Four counties used USGS DEMs as their source. Nine coun- The Magic Bullet mapping s the U.S. Geological Survey’s National Elevation Dataset (NED) moves the nation toward a single, seamless set of topographic data, the recently completed $5.5 million Ohio Statewide Imagery Program (OSIP) provides a blueprint for using LiDAR to create highly accurate, affordable digital elevation models (DEMs). LiDAR trumps traditional surveying and mapping m methods in a State of Ohio imagery project. BY BOB BRINKMAN, CP, PLS, AND BRIAN STEVENS, CP Over the past three years, every square mile of the state was flown to capture consistent, seamless aerial imagery. But the images would have been just pretty pictures without orthorectification, which is usually completed with traditional surveying and photogrammetric methods. The addition of LiDAR to the imagery Above: A LiDAR shaded relief map of Fairfield County, Ohio, with Interstate 70 along the top of the image. ties relied on older models. Five didn’t know the orthorectification source, and 36 counties didn’t respond when asked. Seven counties had used LiDAR. Little did these seven counties know that, in a way, they were pioneers. The State of Ohio’s decision to replace its decade-old black-and-white 1-meter aerial photos with high-resolution color digital imagery began in the late 1990s with an effort led by Stu Davis. As chair of the Ohio Geographically Referenced Information Program (OGRIP), Davis championed a team of key local, state and federal agency stakeholders. The idea was that all would benefit from the imagery— even individuals and organizations, both public and private, beyond the original project participants. Because the images needed to be converted into usable maps, a DEM had to be acquired to support the orthorectification of the new imagery. However, creat- special section: OCTOBER 2009 | Point of Beginning | www.pobonline.com http://www.pobonline.com

Table of Contents for the Digital Edition of Point of Beginning - October 2009

Point of Beginning - October 2009
Contents
Web Site/Digital Edition Contents
Editor’s Points
Newsline
Control on the Edge
Hurricane Watch
The Need for Speed
A Digital Desert
31 Degrees of Latitude
Taming the Wild GIS
The Magic Bullet
From the Ground Up
Professional Topography
Safety Sense
The Business Side
New & Notable
Classified Ads
Fun & Games
Ad Index

Point of Beginning - October 2009

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