Created by Charles T Pett (pett@umd.edu) at the University of Maryland, College Park. This research is funded by NASA PICASSO Grant 80NSSC18K0936.

This file explains how to process raw images from the 'Experimental Method for Measuring Cohesion of Regolith via Electrostatic Lofting' experiment (submitted for publication in PSJ, 2024) and how to reproduce the results and figures in this work. The images were captured by a PCO Dimax CS3 high-speed camera at 945 frames per second.

The 'Run #.zip' files contain the raw image data from the experiment. Run 4 was too large and needed to be broken up into three zip files. Matlab was used to process the images and analyze the trajectories of electrostatically lofted object, namely clumps and individual grains.

Videos: In order to create videos from the images recorded in any of the six experimental runs, use 'writeVideo.m'. There is also an option to save a video of a cropped region. Making videos is useful for identifying lofted objects that can be tracked with 'trackLoftedObjects.m'.

Lofted Object Tracking: 'trackLoftedObjects.m' requires iterative manual input from the user, but the code is well documented to walk the user through. Please reference the commentary in the code for explicit directions. The user will select a beginning and end image within a 'Run #' folder to analyze a clump that the user has identified from the videos. The images are displayed upside down so that the y-axis origin is at the bottom of the image such that positive y-centroid values correspond to a rising object off the surface. The cropped region will then be selected to only include the lofted object of interest. The next section processes the first cropped image in the sequence and initializes the centroid of the object of interest. The following section tracks the centroid of the object over the span of the cropped image, over all images in the chose sequence. If the tracking is not successful, the code will not complete and the user may have to go back and adjust the tolerances, chosen cropped region, etc. If tracking is successful over the image sequence, 'Tracking complete!' will be displayed and the code will output the centroid coordinates of the lofted object over time, the input parameters to initialize the tracking tool, and statistics of the lofted object.

Trajectory Analysis and Cohesion: 'solveCohesion.m' is used to produce all the results of the submitted journal paper, specifically those in Figure 3 and in the Discussion section. The values included in the plots will be listed as workspace variables in Matlab once the code is run. The code directly references the folders in the 'Clumps lofted.zip' and 'Individuals lofted.zip' for quick reproduction of the results from already analyzed lofted object trajectories.

Pixel to mm ratio: The pixel to millimeter ratio was found by analyzing the images in 'Pixel to mm scaling.zip'.

Lofted Clumps vs Lofted Grains: After creating a video of one of the experimental runs, the user manually counts the lofted objects in the video and records the number of clumps and grains. 'grainsVSclumps.m' is used to produce the histogram in Figure 2(c) of the submitted manuscript.