Staff from the Michigan Department of Environment, Great Lakes, and Energy (EGLE) are using Light Detection and Ranging (LiDAR) technology to view the topography (elevation) of the state at a resolution that is 50 times greater than previously existed.
"In fact," says John Esch, geology specialist, "LiDAR has fundamentally changed how we view and interpret the landscape. Often subtle features can be seen in the high-resolution LiDAR topography data that are not visible on aerial photography, topographic maps, and in some cases right under our feet."
LiDAR uses technology that is like a police radar gun where the instrument emits an intense, focused beam of light at the ground and measures the time it takes for the reflected pulses to be detected by a sensor. This produces a densely-spaced network of highly accurate georeferenced elevation points called a point cloud with a point spacing of approximately two feet. Airborne LiDAR is the most common, but there also are terrestrial LiDAR and bathymetric LiDAR.
These elevation points are classified by what the LiDAR pulse was reflected from (ground, vegetation, water, buildings, or other objects). The ground elevation points are used to produce highly accurate Digital Elevation Models (DEMs) that can be used to generate three-dimensional representations of the Earth’s surface and its features, with elevation accuracies that are approximately four inches. An intensity map of the returned LiDAR pulse is produced, and common LiDAR products include DEM hillshade, slope, digital surface models, shaded relief, elevation contours, and automated building extraction.
These DEMs and point clouds can be useful in a variety of settings. Not only have they been used to assist in mapping wetlands, floodplains, and watersheds, but also in mapping coastal and inland dunes, coastal erosion, sinkholes, and in investigation of contamination sites. Many subtle features, especially geologic features, can only be seen using the LiDAR data.
LiDAR has revolutionized how EGLE staff and others view Michigan's topography, hydrology, geology, and land use. This better understanding of the landscape will result in better decisions across state government and will benefit the citizens of the state. LiDAR data collection is funded from a variety of state and federal sources and is publicly available. About 80% of Michigan has been scanned by LiDAR, with the remainder of the state to be scanned this year.
For more information about LiDAR mapping progress in Michigan, please visit the LiDAR status website.