• Use canny, sobel or any edge detection method and allow detection of unwanted edges. Dilate the image to join edges. Run cv::findContours() then find the longest contours. Presumably the longest contours are my desired contours.
• Remove 'weak' edges by blurring the original image with a big kernel. Then run Sobel, cv::findContours() on the gradient magnitude. The problem is this assumes my landscape lines/depth lines are always strong which is not always the case.