Sniper vs. Sniper
A friendly sniper is generally the most effective counter-sniper tool. With similar training, knowledge of the surroundings, and equipment, the friendly sniper can offer advice to the squad, enhanced searching capability, and a means to combat the enemy sniper directly. When told what to watch for, the squad can 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. A sniper duel can frequently distract the enemy sniper from his mission.[citation needed]
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, his 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 only effective at distances of up to 450 meters; 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: The 'sniper detector' system, named Boomerang, was developed through the Defense Advanced Research Projects Agency 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 [1].