Washington State Geological Survey is collecting, analyzing, and publicly distributing detailed information about our state’s geology using the best available technology – LIDAR – an acronym for Light Detection And Ranging. The main focus of this new push for LIDAR collection is to map landslides, but there are innumerable additional benefits and applications of this data both inside and outside of the field of geology. A number of amazingly beautiful and revealing images are featured on the WA-DNR website, along with a trove of information about the technology and it’s applications.
LIDAR is a surveying method that measures very precise distance to a target by illuminating that target with a pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital representations of the target. LIDAR is expensive, but it can easily remove vegetation/grass/trees as it uses an emitting source and interferometry criteria to find the “last echo return” that is assumed as the ground, even in very dense scenarios (forests, corn fields, etc). LIDAR uses ultraviolet, visible, or near infrared light to image objects. It can target a wide range of materials, including non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules.
LIDAR is widely used for many different applications. Some (but by no means all) of those uses include: Geology and Hazards, Forestry, Graphics, Navigation, Meteorology and Fir,e Land-use planning, Archaeology and Agriculture.
In geology, bare earth models allow closer study of geomorphology, which is the study of the origin of the topography of the earth. Floods, faults, landslides, erosion, and glaciers leave their mark on the landscape, and while these marks can be hidden by dense vegetation, they can’t hide from LIDAR.
LIDAR can be used in the field of archaeology to find things hidden by the forest canopy. Large features that would be indistinguishable on the ground are readily apparent in a LIDAR survey, leading archaeologists to sites they might not have otherwise found. For example, intensity returns can be used to detect features just below the surface that affect plant growth.