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Evaluation of Handheld Apple iPad Lidar for Measurements of Topography and Geomorphic Change
  • Peter Nelson
Peter Nelson
Colorado State University

Corresponding Author:peter.nelson@colostate.edu

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High-resolution topographic data are used in geomorphic and hydrologic research for many purposes, including topographic change detection, development of computational meshes for hydraulic models, characterizing channel and hillslope geometry, measuring vegetation structure and density. These data can be collected in a variety of ways, ranging from manual surveying with a Total Station or GPS system, airborne LiDAR, terrestrial laser scanning (TLS), and Structure-from-Motion (SfM) photogrammetry using images collected from drones or pole-mounted cameras. These methods can be very time consuming to collect, and the equipment they require can be very costly. With the release of the 2020 iPad Pro and iPhone 12 Pro, Apple added a LiDAR sensor to their devices, enabling them to be used as hand-held 3D scanners. This new technology has the potential to enable very rapid collection of high-resolution topographic data at low cost. Here, we investigate how well iPad-based LiDAR characterizes topography and topographic change in hillslope and fluvial environments. A 2020 iPad Pro using two apps (3D Scanner and Polycam) was used to collect topographic data over areas ranging from about 100 – 600 m2. These same areas were scanned with a Topcon GLS-2000 TLS system, and aerial imagery were collected with a UAV and processed with Agisoft Metashape to create SfM point clouds. Ground-based targets visible in the datasets were surveyed with an RTK-GNSS system and used to register and scale the datasets. The datasets were aligned using the ICP algorithm in CloudCompare, and cross-sections and topographic differences were extracted from each dataset and compared. Our analysis indicates that transects collected with the iPad LiDAR have mean absolute differences with TLS and SfM data within 3 cm, making these data comparable to other high-resolution topographic data collection methods.