Answer: a GPS capable of accurately measuring elevations to within 10 cm (~4 in)

Answer: a GPS capable of accurately measuring elevations to within 10 cm (~4 in). In the summer of 2019, USGS organized a Light Detection and Ranging (LiDAR) survey of the Kīlauea summit and East Rift Zone, including both the Pu‘u ‘Ō‘ō and 2018 lower Puna lava flows. LiDAR utilizes an airborne laser (helicopter-mounted) to send pulses of light toward the ground, while a sensor detects their reflections back to the source. The precise return times are used to construct a digital elevation model (DEM) of the topography, with greater detail than DEMs derived from other common sources; in this case, the resolution is 25 cm (~10 in). However, the light often returns from objects above the ground, such as buildings, cars, trees, or shrubs. Computers can filter out these returns, but the "bare-earth" surface may still contain small errors. To verify accuracy before the DEM is released to the public, HVO scientists have recently been conducting field checks of the elevations. Here, the GPS in the shrubs is mounted on a 1-meter (~3.25-foot) pole, in order to accurately measure the ground elevation below the vegetation. No native plants were harmed duing the data collection! USGS photos by M. Zoeller.