This story appears in the February 2018 issue of National Geographic magazine.
Satellite images let us see Earth from above. But a technology closer to Earth can give us a much more detailed look.
Aerial “light detection and ranging,” also known as lidar (rhymes with eye-dar), works by sending laser pulses from a plane, helicopter, or drone. The device then receives information back about the surfaces below.
In the past, the highest resolution for lidar was about 40 points per square yard. But a team of researchers at New York University has increased the resolution to 280 points per square yard, resulting in a view from above—especially in urban areas—that’s far more detailed than ever before and true to cracks, curbs, and building facades.
What’s wrong with traditional images from space or miniature scale models? Lidar produces not just an image but a high-resolution geometric representation of a city in motion. Slight slopes in pavement reveal how floodwater will move, and pockets of particulates can identify air pollution.
“Let’s say you worked in public health and you knew there was a high concentration of asthma in one neighborhood,” says NYU’s Debra Laefer, professor of urban informatics. You could start looking at corners where trucks idle, she says. Where is that pollution going? Can we change the vegetation on the roof, the water flow, which roads trucks use?
Collecting data from the air isn’t cheap. But a lidar scanner can be affixed to craft that fly for other purposes, such as police or paramedic helicopters. The team started with a scan of Dublin’s city center. Future flights are possible for more cities—as is releasing the data to city planners, businesspeople, and anyone else who might serve a community.
How lidar can be helpful
Building integrity: Tunneling under cities for subways or sewers can cause damage to overlying buildings. Evaluating building facades during excavation can help identify vulnerable parts of historic properties.
Urban planning: Where will shadows be cast? Will a street have too much wind for pedestrians to walk? Where is a flood likely to start? Developers can benefit from a detailed geometry of how a city lives and breathes.
Disability access: A high curb or a single step into a restaurant may prevent access by people with limited mobility. Data collected can help inform new development or be used in a mobile app that suggests the best route.
Tree trimming: A comprehensive map of a city’s trees can identify which ones are likely to interfere with power lines and which should be trimmed ahead of storms that could knock them down on houses or cars.