Low-Cost Photogrammetry Technique That Uses a Locally Defined Coordinate System to Model Meter-Scale Cavities or Vertical Features
Mya Thomas , Alison Graettinger
Affiliations: Division of Natural & Built Environment, University of Missouri-Kansas City, Kansas City, Missouri, United States
Presentation type: Poster
Presentation time: Monday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 135
Programme No: 3.1.27
Abstract
Photogrammetry is a useful technique in geoscience to generate three-dimensional models of geologic targets for detailed quantification. The proposed low-cost alternative relies on a local coordinate system to compensate for the challenge of collecting accurate GPS coordinates. This method is particularly useful to measure vertical surfaces, subsurface cavities, or other features at the meter-scale. Typical photogrammetry methods include the use of an unmanned aerial vehicle or terrestrial LiDAR technology. These methods can be impractical when GPS-based ground control points are challenging to define due to limited access, flight restrictions, or the target feature being underground. The proposed method uses 7.5-centimeter wooden cubes to define a coordinate grid within or around the feature of interest. X, Y, and Z coordinates are defined from an origin cube and photographs are captured then processed in AgiSoft Metashape to generate a digital three-dimensional model. This technique was executed to model three <2-meter diameter lava tubes (MT009, MT011, and MT012) in the 1961 lava flow at Askja, Iceland. The average percent errors of these lava tube models are as low as 5%, demonstrating the efficacy of the method in capturing subsurface cavities with high accuracy. This technique demonstrates an inexpensive approach to digitally model meter-scale geologic targets that are inaccessible. The generated models are proven to yield accurate measurements which enables detailed quantification that doesn't require physical revisitation.