Juneau Nature

Natural & cultural history of Juneau & Southeast Alaska

Juneau Nature - Natural & cultural history of Juneau & Southeast Alaska

LiDAR: cartographic game-changer

If you clicked-open this page, you obviously have no fear of acronyms. In fact you’re probably more tech-savvy than me [RC]. My goal here is not to explain what LiDAR is, so much as what it can do for those of us in Juneau, Alaska, who—thanks to the foresight of land managers at the City and Borough—were suddenly gifted with this extraordinary technology in 2014.

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.

landforms on LiDAR bare-earth

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.

But what’s just “noise” to geologists is a goldmine to forest ecologists.

Oblique view and belt profile through the LiDAR 'point cloud.'

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.