Over the last few weeks, new aerial photography covering both Kenton and Campbell Counties has been captured for LINK-GIS partners. This photography will provide some of the most detailed views of these counties ever seen, and will include the capability to measure the vertical heights of buildings, towers, and other objects on the ground.
While LINK-GIS partners have had vertical measurement capability for several years now, what’s different is the resolution of the new photography. These images, flown by Pictometry, are created using an updated, high resolution aerial camera system which captures finer detail than in the past. To enable the vertical measurement capability, an accurate model of ground elevation is essential, so LINK-GIS provided its highly detailed LiDAR elevation data to Pictometry for this element.
LiDAR, an acronym for Li
anging, is a highly-accurate method of measuring ground elevation using laser distance measuring equipment mounted in a plane. As the plane flies over an area, the LiDAR equipment sends out tens of thousands of light pulses per second, painting a pattern of dots on the ground, and then measures the time required for each pulse to bounce back to the plane. At the same time, the altitude, position and orientation of the plane is continuously recorded. The collected information is then processed to produce a detailed elevation model of the earth’s surface.
“The camera system Pictometry uses captures five images at a time – one each in the forward, backward, left, and right, or ‘oblique’ perspectives from the plane, and another facing straight down,” said Tom East, Senior GIS Specialist at NKAPC. “At the time of each exposure, computers on board the plane capture the plane’s exact position over the earth using GPS and the exact time of exposure.”
“Also captured are its altitude, bearing, tip, tilt, and roll angles so that all perspectives of each image exposure are known. Later, during processing, this information is used to reduce or eliminate distortions in the imagery,” according to East.
The final result is a model consisting of thousands of images, assembled so that the viewer has a “birds-eye” view of the ground from all five cameras. The user can then move to nearly any location over the ground and see a detailed view of the earth below.
Local law enforcement and emergency response agencies find this information valuable when responding to dangerous situations. The images can also save time and money for county property valuation administration (PVA) offices by reducing the need to go into the field.
Delivery of the new imagery is expected to be complete by the end of July.