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Lidar mapping is a technology of precision terrain measurement that uses laser reflection and time delay analysis to develop accurate surface modeling. It is sometimes referred to as laser-radar, but radar depends upon the reflection of radio waves while lidar relies upon light detection and ranging to gauge elevation data. It can be employed from helicopters and fixed-wing aircraft or ground-based systems. The speed of light is a constant, measured against laser pulses and reflections to determine elevation. Lidar produces near-infrared spectral data both night and day, which can map terrain despite above-ground features like trees or structures.
Applications of lidar mapping include any field in which terrain contour-mapping is essential. Sciences such as archeology, geology, and geography use the technology. Seismology and atmospheric physics benefit from lidar's sensitivity to fluctuating atmospheric factors. Lidar is used in floodplain mapping, in the calculation of forest biomass data, transportation mapping, and urban modeling. Bare earth lidar reveals underlying terrain characteristics, while reflective-surface lidar data enhance analysis in urban planning and visualization.
Advantages of lidar mapping over conventional photogrammetry include high vertical accuracy, more efficient data gathering and processing, and versatility in varied environmental conditions. Lidar mapping typically employs laser emission and detection technology, scanning and control mechanics, a global positioning system (GPS), and an inertial measurement unit (IMU). These calculate precise XYZ coordinates of the targeted reflective surface. Other components may consist of a high-accuracy timer, high-performance computer, and a high-capacity data recording device.
Another key difference between lidar mapping and radar is resolution. Unlike radar, narrow-beamed lasers permit high-resolution, precision reflections. Three-dimensional topographic images can be drawn from the data sets that illustrate many chemical compounds more clearly, due to their proximity to the visible spectrum. Lidar's shorter wavelengths make the technology a key tool in analysis of aerosols and cloud particles in meteorology and atmospheric research. By combining different types of lasers in remote mapping, it is possible to measure subtle changes in reflection intensities of wavelength-dependent atmospheric phenomena.
Laser range finding provides three-dimensional models of surfaces or structural features like buildings, trees, and natural boundaries. Lidar mapping relies not only upon multiple lasers, but also on multiple timing effects to measure first and last reflections in order to tell low and high points. This provides precision feature elevation data. While lidar cannot penetrate tree canopies, enough laser data finds its way through breaks in the foliage to measure distance to ground. Other applications include traffic enforcement using vehicle-specific speed guns, physics and astronomy, various environmental sciences, and land or property surveying.