UMass Boston

DWEL: The Dual Wavelength Echidna Lidar


dwel, instrument, lidar, forest


The Dual-Wavelength Echidna Lidar (DWEL) collects simultaneous scans of forests with two lasers at different wavelengths, 1064 nm (near-infrared / NIR) and 1548 nm (short-wave infrared / SWIR). Power returned from leaves is much lower than from woody materials such as trunks and branches at the SWIR wavelength due to the liquid water absorption by leaves, whereas returned power at the NIR wavelength is similar from both leaves and woody materials. This spectral contrast between leaves and woody materials, along with spatial context information. discriminates leaves and woody materials accurately in 3-D space, thus allowing the measurement of separate leaf and woody area profiles. 

DWEL Design:

dwel, mirror, lidar


DWEL instrument schematic (Douglas et al., 2015). Thin lines represent the outgoing, coaxial beams. Gray lines represent the field of view of the instrument and the path of observed returns. The green laser serves as a marker for laser alignment and is not recorded.

DWEL Data: 



A bi-spectral point cloud generated from the simultaneous 1064- and 1548-nm
scans at a Harvard Forest plot in the leaf-on season. The color of each point
is rendered as the composite color from the apparent reflectance at the two
wavelengths, red as 1548-nm, green as 1064-nm and blue as dark constant.
Leaf points are greenish, woody points are yellowish. 



Two animations of the Pgap for the leaves (top panel) and woody materials (bottom panel)
changing as the range goes further. Dark red or dark green is the Pgap of zero, meaning a laser
beam is fully intercepted by woody materials or leaves respectively. The white is Pgap of one,
meaning a pure gap that the whole laser beam goes to the sky. Light red or light green means
a laser beam is partially intercepted. 


Professor Crystal Schaaf’s Lab

School for the Environment
University of Massachusetts Boston
100 Morrissey Blvd.
Boston, MA 02125