Comments on circular vs. elliptical errors in automatic location identification

Currently foreseen automatic location identification (ALI) technology has allowed the FCC to adopt a requirement that service providers allow ALI within 125 m for a certain fraction of calls. We must take into account the fact that that is a large area; emergency units responding to a call may not immediately find the emergency due to intervening obstacles. In this case it may mean the difference between life and death that they be provided with an efficient search area. We find that a circular search area, as implied by the radial requirement, is often very inefficient. We analyze this situation and demonstrate that an elliptical area, which may be calculated easily from the measurements, is superior