An obstacle detection system includes an object detection system, an alert system, and a controller. The controller is configured to store an electronic map containing a known obstacle, store known and unknown obstacle warning zones, and detect a detected object in proximity to the machine. The controller is further configured to compare the detected object to the known obstacle to determine whether the detected object is a known obstacle or an unknown obstacle, generate a first alert signal if the detected object is a known obstacle and within the known obstacle warning zone, and generate a second alert signal if the detected object is an unknown obstacle and within the unknown obstacle warning zone.