Aerial Lidar – Case Study
NEW YORK CITY SOLAR MAPPING INITIATIVE
Sanborn was engaged to acquire, process and deliver a 3-Dimensional Lidar point cloud dataset critical to a New York City Program designed to improve the environment, build the economy, and enhance the quality of life for all New Yorkers. ‘PlaNYC’—is under way with the long-term goal of cutting greenhouse gas emissions by 30% by the year 2030. An important facet of this goal includes a critical solar energy program geared toward the development of cleaner, more reliable and renewable energy sources. The Solar Energy initiative is being championed by The City University of New York and the implementation and analysis is being managed at the Center for Advanced Research of Spatial Information (CARSI) at Hunter College, New York.
The project coverage and Lidar density demanded 440 flight lines, over 15 billion points and close to 1 TB of data. Two Aircraft and two Leica ALS 50 II Lidar sensors were utilized to complete the acquisition over a two week time period in April, 2010.
CUNY is using the final 3D-building model to calculate the intensity of Insolation for every building throughout NYC. The information will be used to calculate the return of investment for homeowners who install solar panels on their rooftops. Con Edison also was involved in the program and provided solar panel calibration information for making ROI calculations more accurate. The data is available through an interactive website for all NYC residents to evaluate the cost savings for solar installation on their homes, and contribute to the strategic goal of making NYC greener. In addition to being utilized for Solar Energy initiative applications, the data will be shared with other City agencies and utilized for any variety of additional GIS applications.
LIDAR ACQUISITION SPECIFICATIONS
- Altitude – 1066m/~3497 ft (The Empire State Building stands at 1,453’)
- FOV – 28 degrees
- Air speed – 120 knots
- Laser Power – 94.7 Khz
- Normal Collection Window – 1-5am
- Base Stations – Five utilized to support/verify the accuracy of the AGPS
- Checkpoints – Twenty-two
- Flight Lines – 440
To develop the accurate 3D Building Models required for the project, Sanborn executed aerial missions to acquire Lidar data over 15 days during April 2010. Two aircraft, each equipped with a Leica ALS 50 II sensor were deployed to acquire the Lidar over all five NYC Boroughs covering an area of approximately 360 square miles. An unprecedented density of points (8-12 points per square meter) were collected to accomodate the number of tall buildings and urban environment. The project required 440 flight lines that at times contained large areas of overlap and required independent calibrations.
LIDAR PROCESSING AND DELIVERY
Due to the complexity of the project area and different values applied based on the terrain slope, proximity of adjacent points and the structure of these points, the Lidar filtering process required adjustments for different algorithms. Localized processing and adaptations to the filtering process were paramount in guaranteeing a product that meets or exceeds the Lidar product specifications.
As part of the data accuracy QC, CUNY acquired 1,290 independent checkpoints distributed throughout the five Boroughs, surveyed by Con Edison to an accuracy of 2 cm. These ground control points were then used to determine a Root Mean Square Elevation (RMSE) vertical accuracy difference between the Lidar data and ground control points.
The final RMSE throughout the project area was 7.48 cm (planned accuracy was 10 cm).
SOLAR ENERGY AND INSOLATION
Calculating the intensity of INcident SOLar RadiATION (Insolation) is determined by several factors that include:
- Latitude and elevation
- Atmospheric condition
- Seasonal and daily shifts of sun angle
- Orientation (slope and aspect)
SOLAR MAPPING SAMPLE IMAGERY
LiDAR CASE STUDY
LiDAR OPERATING PRINCIPLES
For more information or to order Sanborn LiDAR products or services, call Sanborn customer service at 1.866.SANBORN (1.866.726.2676), or contact us by e-mail at firstname.lastname@example.org.
Read more about the New York City Solar Mapping Initiative in The New York Times, or click below to download a PDF New York City Solar Mapping information sheet.