Laser “Radar” Maps NYC’s Solar Power Potential

Recently, New York City has been employing low-flying twin engine planes equipped with light detection and ranging (LIDAR) capability in order to determine which areas are best suited for solar energy as well as empowering the city to better prepare its emergency response system.

LIDAR will enable NYC to prepare a 21st century version of Robert Moses' "Panorama" to optimize solar panel installation.

“The purpose is to try to give people the tools they need to understand how to adapt solar technology,” Tricia Case, City University of New York (CUNY) director of sustainability told the New York Times. “With the Lidar data, we’ll estimate the solar potential for every building in the city.” CUNY is assisting in the venture.

The objective is to map structures, elevations, sun and shade, amongst assorted nooks and crannies unique to the city.

According to Rohit T. Aggarwala, director of NYC Office of Long-Term Planning and Sustainability, the project will result in a picture of New York’s physical space “in far more detail than what we had before.”

Part of Mayor Michael R. Bloomberg’s environmental agenda entitled PlaNYC, the project will cost approximately $450,000.00. The venture is financed in part with $205,470 from the federal Energy Department.

Among the many uses for the data, in addition to providing information for the most efficient placement of solar panels, is to create updated maps of the areas most prone to flooding.

New York City’s most recent flood plain maps date back to the 1980s and were made using contemporary aerial photography and ground surveys.  Aggarwala claims that these new maps will be far more accurate and comprehensive.

LIDAR uses a "small footprint" to measure topography. Each laser pulse usually measures a range from 6 inches to 3 feet in diameter at ground level.

Federal Emergency Management Agency officials claim that other cities such as San Francisco have already developed solar maps, using LIDAR. Images of surface terrain and structures are captured by shooting 100,000 laser pulses per second from an aircraft and measuring the time it take the pulses to bounce back, producing representations of what it hits.

LIDAR differs from conventional radar primarily in its use of shorter wavelengths.  In general, features of an object can only be imaged at the same size as the wavelength or larger.  LIDAR’s relatively smaller wavelengths enable finer imagery. However, LIDAR tends to be more susceptible to errors from aerosols or cloud particles.  Thus, the need for low flying aircraft to ensure accurate data collection.

The rooftop data accumulated through LIDAR can be used to create an online “solar map” that will help assess the city’s capacity for solar power and even enable New York to verify which buildings are suitable for solar panels.

For the 1964 World’s Fair, Robert Moses created the Panorama, an architectural model of the City over 9,000 square feet large depicting over 900,000 buildings, bridges and topography.

“It’s going to be that,” Mr. Aggarwala said, “but more accurate and digital.”

New York hopes that the solar and flood maps will be completed by the end of 2010.