Micro-terrain and canopy feature extraction by breakline and differencing analysis of gridded elevation models : identifying terrain model discontinuities with application to off-road mobility modeling

Abstract

Elevation models derived from high-resolution airborne lidar scanners provide an added dimension for identification and extraction of micro-terrain features characterized by topographic discontinuities or breaklines. Gridded digital surface models created from first-return lidar pulses are often combined with lidar-derived bare-earth models to extract vegetation features by model differencing. However, vegetative canopy can also be extracted from the digital surface model alone through breakline analysis by taking advantage of the fine-scale changes in slope that are detectable in high-resolution elevation models of canopy. The identification and mapping of canopy cover and micro-terrain features in areas of sparse vegetation is demonstrated with an elevation model for a region of western Montana, using algorithms for breaklines, elevation differencing, slope, terrain ruggedness, and breakline gradient direction. These algorithms were created at the U.S. Army Engineer Research Center – Geospatial Research Laboratory (ERDC-GRL) and can be accessed through an in-house tool constructed in the ENVI/IDL environment. After breakline processing, products from these algorithms are brought into a Geographic Information System as analytical layers and applied to a mobility routing model, demonstrating the effect of breaklines as obstacles in the calculation of optimal, off-road routes. Elevation model breakline analysis can serve as significant added value to micro-terrain feature and canopy mapping, obstacle identification, and route planning.

Tutorial : the DEM Breakline and Differencing Analysis Tool—step-by-step workflows and procedures for effective gridded DEM analysis

“…The following is a brief overview of the IDL Breakline Tool output product overlays and supporting algorithms. A more detailed treatment of the underlying computational approach can be found in the ERDC/GRL Technical Report "Micro-Terrain and Canopy Feature Extraction by Breakline and Differencing Analysis of Gridded Elevation Models" (Blundell 2021). A user guide for the Breakline Tool, providing a comprehensive description of GUI operation and functionality, is also available with the title "User Guide: The DEM Breakline and Differencing Analysis Tool" (Blundell 2022) and should be consulted before performing the tutorial exercises given here.…”

User guide : the DEM Breakline and Differencing Analysis Tool—gridded elevation model analysis with a convenient graphical user interface

“…The basic algorithms dedicated to creating output products perform calculations for (1) breaklines, (2) elevation difference, (3) slope, (4) terrain ruggedness, (5) breakline gradient direction, and (6) three types of surface optima: saddle points, peaks, and depressions. A more thorough treatment of the algorithms is provided in the ERDC/GRL Technical Report Micro-Terrain and Canopy Feature Extraction by Breakline and Differencing Analysis of Gridded Elevation Models (Blundell 2021).…”