LidarBoX: a 3D-printed, open-source altimeter system to improve photogrammetric accuracy for off-the-shelf drones

Drones provide a privileged birds'-eye view for collecting high-resolution imagery for morphometric and behavioral sampling of animals. Biologically meaningful measurements extracted from overhead images require an accurate estimate of altitude, but current commercial drones include inaccurate barometer estimates. Recent proposals for coupling altimeter systems to drones have provided customized, open source solutions; yet assembling such altimeter systems requires advanced technical skills, thereby potentially limiting their use. Here, we built upon recent advances to provide a 3D printed enclosure for an altimeter system that is inexpensive, self contained, easy to set-up, and transferable across commercial drones. We depart from a published, successful data logger system composed of a GPS and LiDAR sensor, and design a more compact and self-powered version ("LidarBoX") that easily attaches to a variety of commercial drones. We compare flight times with/without LidarBoX attached, test flight maneuverability and performance, and validate reliability of measurement accuracy. To make LidarBoX accessible, we provide an open-source repository with design code and files and a how-to assemble guide for non-specialists. We hope this work helps popularize LiDAR altimeter systems on commercial drones to improve the accuracy and reliability of drones as a sampling platform for ecology and wildlife research.