February 21, 2013

Technical Issues Delay Fence Removal

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Two years after a string of suicides led the University to erect fences around bridges on and around campus, Cornell decided it would replace the fences with nets hanging under the bridges. Though work on the nets was scheduled to be completed by the end of 2012, the fences will remain on the bridges indefinitely until remaining issues with their technology are resolved, according to John Keefe, project manager.

Each bridge is equipped with cameras that are designed to detect heat so that emergency personnel can be notified when someone has jumped or fallen into the nets and needs to be rescued. Currently, however, the cameras are too sensitive, according to Keefe.

“The basic problem is we’re getting too many false alarms, and we need to calibrate the sensors so that they detect a human, but don’t detect a squirrel,” he said. “We’re trying to find the sweet spot.”

Winter Storm Nemo and other storms may have caused problems with the heat-detecting cameras by creating “optics of extreme temperature variance,” or drastic shifts in temperature, according to University Architect Gilbert Delgado.

“We had the system basically operational before the recent storms, and after the storms we had to calibrate, so the weather may have had something to do with it,” Delgado said. “The extreme weather revealed that we had to do some additional calibration work [on the thermal imaging cameras] before we commissioned the system.”

In addition to suffering delays caused by issues with the thermal camera, the nets’ installation was held up in part due to problems shipping materials for their construction, an issue which has since been resolved.

“The mesh system comes from Europe. There was a minor hiccup at one point that affected the delivery of the mesh systems,” Delgado said.

Keefe said that changes in weather may affect the effectiveness of the thermal imaging cameras in the future.

“If there’s a branch in the way and the breeze catches it the wrong way, it triggers the alarm,” he said.

The University is still in the process of determining how long it will take before the thermal cameras are fully operational and the fences can be removed, according to Delgado. Completion of the project was originally scheduled for the end of 2012.

On Monday, workers adjusted the sensors on four of the bridges for a trial period of several weeks, according to Keefe.

“We reset four cameras to the best of our capabilities, and we’ll track that for false alarms, and if that works we’ll do it for all the bridges and track them. If that works, we’ll link it to [the Cornell University Police Department],” he said.

However, the timeline for the changes is still undecided, according to Keefe.

“The timeline is really pretty variable right now,” he said. “If that works, it’s probably another couple of weeks [from now until completion]. If that doesn’t work, I’m not really sure what we’re going to do at this point.”

Although, Cornell’s net system is based off a similar system in use in Switzerland, the University’s use of thermal imaging cameras in conjunction with the nets is unprecedented. As such, Cornell does not have a model to follow when calibrating the cameras, Delgado said.

“The Swiss system did not have a detection system,” Delgado said. “This is a new application of the camera. This is the first installation of this type of mesh and this type of camera perhaps in the world. We are developing and testing this system before anyone else is.”

Come summer, Cornell may need to readjust its thermal sensors, Keefe said.

“We’re not sure if the differences in temperature are going to affect it. The summer and winter are a little bit different, obviously, so we need to look again in the summer to see what it looks like,” Keefe said.

Unlike the six other bridges, the Suspension Bridge will not have nets installed directly under it. Instead, a similar system — in which the mesh is wrapped around the bridge — will be installed at the site at the end of March.

“It is sort of [like] wrapping a sock around the entire bridge,” Keefe said.

Original Author: Joseph Niczky