title: How to determine which regions, each defined by longitude , latitude and a radius, contain a given location?
body: <p>I have a large data set of regions , each of which is defined by a longitude, latitude and a given radius.  I have a location point with a  a latitude and longitude and I need to determine  which of the regions contains  my point.</p>
  
  <p>Currently I am using brute force : I compute the distance between the target point and  each region's center longitude and latitude ; if the distance is less than the radius of the region, I include the region in in my result.
  Obviously this solution is not tenable. </p>
  
  <p>Can GeoHash be used to formulate a solution ?</p>
  
  <p>Edit : The business problem is given a set of cell phone with known ranges and a fixed set of  available locations owned by a real estate holding, where is the place for a signal repeater.  There are other considerations of course besides location and distance. Otherwise someone will have drive around the country with a signal detection kit -- not optimal . Not a homework question. I have Comp Sci background but GIS is new to me and I am willing to learn. </p>
  
  <p>Edit : I will continue using brute force across several ec2 instances. Not the most optimum solution but it works. Thank you all for proposed solutions but unfortunately given the time and knowledge constraints and vagueness of the methodology, I am not going to be able to try them out.</p>