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LiDAR Derived Products

LiDAR SHORELINES - Click on the map below

LiDAR Data for other products

Lidar is a remote sensing technique that is a very valuable tool when working in coastal area (or any area); the acronym stands for LIght Detection And Ranging (it used be written as LiDAR). I will be using them for flood mapping, marsh migration, shoreline change and pretty much any final product - they can help out with lots of different processes.

I will not get too deep into the subject but just a couple things. Lidar is an ‘active’ sensor, which means the sensor provides the energy that it subsequently measures after bouncing off ‘stuff’ - a passive sensor (e.g., a aerial image) measures energy that is provided by something else (e.g., the sun). Lidar is like sonar and radar but uses a laser (light) source instead of sound or radio waves. It can not (!) go through trees, but so many laser pulses are fired (like 250,000 per second) that there are enough in most cases that some can get through and are reflected back. The images to left are examples of early lidar (c. 1997) and present day data sets (c. 2017). Some systems (blue-green wavelength systems) can penetrate water depending on the clarity, but most (infra-red systems) will reflect off the water surface. In SC the water is, as you know, not too clear so in most cases you can get a meter or so of water penetration.

In general Digital Elevation Models (DEM) are the primary outputs you will see, but there are also reflectance or ‘intensity’ images that can be used with the elevation data to provide information about what is being measured. In that regard, there are typically two types of DEM surfaces - a ‘bare earth’ DEM that has all ‘stuff’ on the earth’s surface removed and a Digital Surface Model (DSM) that captures the top surface. You would use a DSM if you were looking at installing a tower and interested in what the view-shed of it would be; I also like it for looking at tree and vegetation heights.

So, I must confess I am a lidar ‘geek’. I have been using it for over 20 years to look at coastal change (first time in 1999 to look at the effects of Hurricane Georges and culverts on Mississippi beaches). I have worked on a 2017 data set (the most recent) and will be using it to do a bunch of analyses. By the way, Sullivan’s Island is one of the areas in the US (world!) to have a twenty year history of lidar data - the earliest data, albeit a very early vintage, was captured in 1996.

As you can see in the adjacent figures lidar captures a lot more than just the ground. This data set has been classified (each point assigned a class based on what it reflected from) using a very thorough process (automated and manual). It is much more detailed data set than most, and maybe a bit overboard. My goal is to see what can be done with all that additional information. Of course I will use the points to make a DEM for inundation/flooding. But I would also like to see if I can use the additional information to aid in vegetation studies, marsh migration, and infrastructure risks - and hopefully more.