LiDAR Archives | JuneauNature

If you clicked-open this category, you obviously have no fear of acronyms. In fact you might be more tech-savvy than me. My goal here is not to explain what LiDAR is, so much as what it can do for those of us in Áak’w & T’aakú Aaní, land of Auk and Taku people (CBJ), who—thanks to the foresight of land managers at the City & Borough—were suddenly gifted with this extraordinary technology in 2014. With Koren Bosworth, Cathy Pohl and Andrew Allison, I used LiDAR every day in the most intensive ground-truthing project of my career. It lifted our work to a new level of accuracy, efficiency, and interpretive sophistication.

Landforms from RD Miller’s 1972 surficial geology map, overlaid on LiDAR-generated ‘bare-earth.’ Streams are also predicted from the LiDAR digital elevation model (DEM). Our ground-truthing in 2014 found these to be quite accurate.

LiDAR is so arcane and geeky that people actually argue about what the acronym stands for. (“Although thought by some to be an acronym of Light Detection And Ranging, the term lidar was actually created as a portmanteau of ‘light’ and ‘radar”‘) For our purposes, think of a small plane at about 3000 feet, shooting down millions of light pulses, reflected back, carrying information about topography. For what’s called the bare-earth model, all the LiDAR returns from vegetation are filtered out.

But what’s just ‘noise’ to geologists is a goldmine to forest ecologists. The

Oblique view and belt profile through the LiDAR ‘point cloud.’ From our desks we can now measure the height of any tree in Juneau to the nearest foot.

LiDAR point cloud can be reassembled, for viewing either in a rotatable 3D model (upper example), or side-view profile (belt A-B, below). This example is from the formerly tidal uplift meadows near Eeyák’w, small rapid (Amalga Salt Chuck).

Since the CBJ LiDAR commission in 2013, other communities have jumped aboard. As of 2018, it’s available for the road systems of Ketchikan and Sitka. Hoonah has LiDAR for a much larger area—what they define as the Hoonah Community Forest. And even larger is the recent LiDAR project for the northern two thirds of Tàan, sea lion (Prince of Wales Island).

In the links below I’ve listed several slide shows that detail the use of LiDAR for different mapping and interpretive projects. New tools for old naturalists was a talk for the USFS Fireside series, with many examples of the use of LiDAR in wetland mapping, landform interpretation, and big-tree hunting. Supplement to the CBJ wetlands surveys gives more technical background.