1. An imaging system for determining a plane, comprising: a processor configured so as to receive a depth image, wherein the processor is configured so as to divide a portion of a depth image into a plurality of areas, fit a two-dimensional line to depth points in each of the plurality of areas, and combine two or more of the plurality of two-dimensional lines to form a three-dimensional plane estimate, and wherein the plurality of areas are greater than one pixel in each direction, the processor being further configured to fit the two-dimensional line by: dividing the area into a plurality of scan lines; selecting a depth point with a highest depth value out of a set of the depth points on each of the plurality of scan lines; discarding depth points which are not further away than a farthest depth point on an adjacent scan line of the plurality of scan lines; and fitting remaining depth points of the set of the depth points so as to calculate the two-dimensional line.