also act as additional eyes and ears for the friendly sniper. Aside from watching over the squad, the friendly sniper also has the option to detach and engage the enemy sniper. Without any outside help from the squad, the respective skills of each sniper play a significant role in determining victory. You can also determine the enemy snipers skill by the accuracy of their bullets and their precision of their shots. This can also play a key role in determining victory. Triangulation: technique at two or more locations can more accurately identify the position of a sniper at the time of firing. Sound delay ("crack-bang"): The enemy's supersonic bullets produce a sonic boom, creating a "crack" sound as they pass by. If the enemy's bullet speed is known, their range can be estimated by measuring the delay between the bullet's passing and the sound of the rifle shot, then comparing it to a table of values. This is effective at distances of up to only 450 metres; beyond this, the delay continues to increase, but at a rate too small for humans to distinguish accurately. Also, in urban areas, the sound can give inaccurate results because the buildings in the area can relay false sound directions. Detector: A 'sniper detector' system, named Boomerang, was developed through DARPA and can determine the bullet type, trajectory, and point of fire of unknown shooter locations. The system uses microphone sensors to detect both the muzzle blast and the sonic shock wave that emanate from a high-speed bullet. Sensors detect, classify, localize and display the results on a map immediately after the shot. The system sensors are usually mounted on a vehicle. The United States military is also funding a project known as RedOwl, which uses laser and acoustic sensors to determine the exact direction from which a sniper round has been fired. The RedOwl system has been tested on the PackBot robot from iRobot Corporation. Counter-attacking the sniper Once a sniper's position is known or suspected, other options follow: Fire support: If the sniper's general position can be determined by other means, the area can be bombarded by mortars, artillery, or close air support. Rockets, guided missiles, anti-armor/anti-fortification weapons and other direct fire options may also be used by the forces in contact, as well. Smoke screen: In urban settings or other environments with limited movement and fields of view, smoke can be