MS-HLMO中Partial main orientation map(PMOM)是作为特征图以供后面统计直方图。其计算方法被称Average Squared Gradient(ASG)计算公式如下:
G P M O M = 1 2 a r c t a n 2 ( ∑ σ ∑ W σ G x 2 − G y 2 , ∑ σ ∑ W σ 2 G x G y ) G_{PMOM} = \frac{1}{2}arctan2(\sum_{\sigma}\sum_{W_{\sigma}}G_x^2 - G_y^2, \sum_{\sigma}\sum_{W_{\sigma}}2G_xG_y) GPMOM=21arctan2(σ∑Wσ