Techniques are described for determining edge pixels from a depth map in order to identify edges of an object within an environment. The techniques may fit a plane to a group of pixels comprising a subject pixel and neighbors of the subject pixel. Each pixel of the group may then be classified as either an inlier pixel or an outlier pixel, and a ratio of inlier pixels to outlier pixels of the group may be calculated. The techniques then compare this ratio to a threshold ratio to designate the subject pixel as either an edge pixel or a non-edge pixel. Edge pixels designated in this manner may then be used to identify object edges and, hence, objects in the environment.