Unbeknownst to most of us, there is a world of difference between an aerial photograph and an orthophotography. In fact, enough of a difference for the State of Connecticut to get behind an initiative to photograph the entire state.
The results are to be made publicly available through the state’s Open Data Initiative. The orthoimaging of Connecticut, now complete, was undertaken by the Sanborn Map Company, under a contract with the Capitol Region Council of Governments made possible by a grant from the state’s Office of Policy and Management. It will provide Connecticut with its first statewide acquisition of datasets at this high level of accuracy, according to those involved with the project.
The Sanborn flight team overcame challenging spring weather conditions to successfully collect high-resolution imagery of the entire state of Connecticut and its coastline in just five weeks, according to the company. Altogether, the firm collected more than 42,500 4-band, 3-inch resolution images during March and April, including more than 6,000 coastline images during low-tide conditions.
The Sanborn team, which included subcontractors, also collected more than 5,200 square miles of high-density light detection and ranging (LiDAR) data covering the entire state during the same time period. All of the data were collected during snow-free, cloud-free and leaf-off conditions, which makes them ideal for a host of products and applications.
A conventional perspective aerial photograph contains image displacements caused by the tilting of the camera and terrain relief, or topography. It does not have a uniform scale and one cannot measure distances on an aerial photograph as if it were a map.
In orthophotography, the effects of tilt and relief are removed from the aerial photograph by a computer rectification process to create an orthophoto, which then becomes a uniform-scale photograph. Since an orthophoto has a uniform scale, it is possible to measure directly on it, as with traditional maps.
The product combines the image characteristics of a photograph with the geometric qualities of a map; thus, it is possible to get direct measurements of distances, areas, angles, and positions.
That distinction can make a big difference for governments and businesses seeking such images. Brad Arshat, Sanborn director of strategic accounts in the Northeastern United States, estimates that statewide collaboration on the project will result in several million dollars in tax dollar savings, as opposed to each of the state’s 169 municipalities acquiring its own data.
Sanborn is now creating mapping products from the data, which will be delivered later this year. These include 3-inch ground sample distance (GSD) orthoimagery; U.S. Geological Survey (USGS) QL2 LiDAR data; bare Earth digital elevation models (DEMs); and 1-foot contour maps.
Individual municipalities and state agencies also have options to purchase additional products as needed, such as 3-D building footprints, planimetrics, landcover maps, impervious surface maps and more, according to company officials.
“We need to support our communities by giving them the tools to do their jobs in a modern, efficient and effective way,” Gov. Dannel Malloy pointed out in a Sanborn news release. “As a former mayor, I know how valuable this information is to municipalities. In addition, this information is critical to our state agencies.”
Sanborn is a preeminent innovator in the geospatial industry, the company website indicates, delivering state-of-the-art mapping, visualization, Web GIS™ and 3-D solutions to customers worldwide. The firm, which marked its 150th anniversary in 2016, operates a fleet of 14 aircraft located strategically across the United States.
“Our flight team did an exceptional job of outmaneuvering the unusual weather present during the collection period (in Connecticut),” says Shawn Benham, Sanborn project manager. “The savings truly are astronomical when you merge many smaller project areas into a single large project because of the fixed costs associated with each mobilization,” added Arshat in statement released by the company.