by Anthony Deen

NYC Solar Map

It was a little over one year ago that the NY Times wrote about a coalition between Office of City Planning, the City University’s (CUNY) CREST Center and the Sanborn Map Company to survey the entire five boroughs using LIDAR technology.

The acronym LiDAR stands for Light Detection And Ranging, it’s is an optical sensing technology that can measure the distance to an object by illuminating it with light. This technology allows surveys to be made directly from the actual terrain.

Flying at an altitude of 3,500 feet for nine consecutive nights from April 14-30, 2010, New York was “imaged” by a small twin engine plane equipped with a LiDAR gun, shooting 100,000 laser pulses per second, then measuring the time required for the pulses to return.

The benefit of the LiDAR system is that its enhanced images are more topologically accurate. It offers more accurate depth information than traditional imaging techniques, recording the distance between the ground, treetops and rooftops. Each and every solid nook and cranny in the City was documented.

The result is a three-dimensional map of the entire city with more than 900,000 buildings, even more accurate than the famous 9,335 square foot panorama architectural model of the city at the Queens Museum of Art commissioned by Robert Moses for the 1964 World’s Fair.

The imaging project, funded with $450,000 from Mayor Bloomberg’s PlaNYC 2030 has given us three tangible benefits. The first being an accurate map of tree cover in the City, that is helping the Parks Department and City Planning determine where trees are most needed in the City. In the summer trees provide shade and help offset the City’s “heat island” effect. There are several blocks in the Gowanus area that have already benefited from this study.

The second benefit is more accurate topology that helped the City identify areas where potential flooding may occur during hurricanes, storm surges and other tidal events. During Hurricane Irene, this was extremely useful when determining which areas of the neighborhoods surrounding the Gowanus required evacuation.

Unfortunately during the hurricane we also learned that mapping has its limitations. Without intelligent judgement mapping can actually be harmful as when the City directed Red Hook and Carroll Gardens residents to an evacuation center at IS 136 on 4th Avenue in Sunset Park. This required local residents to cross the flood zone (and the Canal) to get to higher ground. Certainly going to any of the schools along Court, Smith or Hoyt streets would have made a lot more sense.

The most recent benefit of the LiDAR imaging is a map showing the rooftop surface area for each and every building in the City that can be used to install solar power. The NYC Solar Map, financed with over $200,000 from the US Department of Energy, approximates the tangible benefits of going solar for building owners (cost of installing solar systems and government incentives ) and represents a viable starting place in doing research if one is interested in making the conversion to solar. The City’s new public private energy efficiency partnership, the NYCEEC, is currently developing ways for small building owners to aggregate their buying power to network and power entire blocks.

These are three impressive, real world benefits from this one mapping project. We look forward to what more will be produced from the LiDAR survey.

The Wall Street Journal has LiDAR images on their website here