This land is your land
For the past two years, Ohio has been capturing color digital aerial photography of the entire state — 88 counties covering 41,276 square miles. Ohio is supplementing the photos with highly accurate elevation data, obtained through Light Detection and Ranging (LiDAR) technology. The Ohio Statewide Imagery Program (OSIP) is among the first in the nation to enhance a state’s geospatial repository with a Digital Elevation Model (DEM) generated from the data.
In pursuing new imagery, state officials also needed accurate elevation point data to make the photos useful for mapping, engineering and planning. So, the state contracted with Dayton, Ohio-based Woolpert to collect digital aerial imagery and LiDAR points, color digital orthophotography and color infrared digital orthophotography to create a LiDAR DEM.
The LiDAR data — billions of points representing three-dimensional (3-D) terrain, waterways, roadways, buildings and tree cover — was used to create 3-D DEMs. Two-dimensional aerial images can be draped over the DEMs so the scale of the imagery is uniform, to create maps that can be used to measure true distances.
OSIP provides the data to each Ohio county and posts it online for public download from the OGRIP Web site (http://ogrip.oit.ohio.gov). Using a variety of off-the-shelf GIS software, counties can view the LiDAR and DEM data in 3-D, rotate it and view it from different angles, and analyze it.
The imagery and LiDAR data already are being used for many federal, state and local projects. For example, the Ohio Department of Transportation and the Ohio Department of Natural Resources (ODNR) are using the information to predict landslides and model scenarios for dams.
Williams County engineering crews have been using the data to identify problems in watersheds, and plan construction and maintenance for ditches, roads and bridges. “We still, as a matter of safety, verify with field survey as necessary and compare it to the LiDAR, but the new data is so accurate, it is replacing a lot of field surveying, often at time-savings of 75 percent,” County Engineer Dennis Bell says.
The DEM data is being integrated into the U.S. Geological Survey (USGS) National Elevation Dataset, improving the national map’s accuracy. Additionally, all of OSIP’s LiDAR data will be integrated into USGS’s Center for LiDAR Information Coordination and Knowledge, a national database for disseminating LiDAR data for scientific needs. Federal partners will use the data for urban line-of-site models, flood studies, terrain modeling, and production of new topographic maps and integrated framework data in Ohio. “OSIP has become a blueprint for a larger goal to create a seamless and highly accurate imagery dataset for the nation,” says Stu Davis, administrator for OIT Enterprise Shared Services and OGRIP chair.
Statewide imagery collection
Office of Information Technology (OIT), Ohio Geographically Referenced Information Program (OGRIP)
Dayton, Ohio-based Woolpert
2006 – 2009