Automatic Detection of Orientation of Mapped Units via Directional Granulometric Analysis

Automatic detection of orientation of mapped units via directional granulometries is addressed in this letter. A flat symmetric structuring element (B) of size 3 × 3 with nine elements, which is a disk in eight-connectivity grid, is decomposed into four 1-D directional structuring elements (B
ⁱ
s). Multiscale opening transformations are performed on each mapped unit with respect to these four directional structuring elements to eventually compute direction-specific morphologic entropy values. Based on these values, the orientations of mapped units are classified into four classes that include those units with orientations of: i) South East-North West (B
¹
), ii) North-South (B
²
), iii) South West-North East (B
³
), and iv) East-West (B
⁴
). We demonstrated this approach on five model objects, and nine major river basins extracted from DEM of Indian peninsular. This approach yields quantitative results, based on which the mapped units could be automatically classified into four different orientations.