Cell Phone Triangulation – The Basics
Cell phones have an amazing amount of data on them:pictures, call logs, contacts, text messages, etc. One of the things that most modern cell phones have is GPS (Global Positioning System) data. GPS information allows one (or anyone else for that matter) to find out where you are in the world. But what if you don’t have GPS? Your phone still knows where you are, albeit only roughly.
The process is relatively straight-forward, but the average citizen on the street rarely has access to this kind of information in order to determine a cell phone’s location.
First a lesson on how cell phones interact with towers. Cell towers are everywhere. They are what make up the network that we all use to communicate with each other by cell phone. The way you connect with these towers is generally by signal strength and how many people are connected to a tower at that point in time. This means (and what makes triangulation not an exact science) is that you can be standing right underneath a cell tower, but really be connected to one five miles away.
Depending upon the cellular carrier’s system, you may be connected to multiple towers at once. Alternatively, as you move around, you change towers. All the while, multiple towers may “see” the
phone as it moves.The way that triangulation can estimate your location, is by taking the tower that the phone is connected to (again, may not be the closest one) and drawing a circle around the tower which would depict the coverage area for the tower. The phone being located is somewhere inside that circle. This process is repeated with the next one to two towers, until you are left with overlapping circles. In theory, the phone being sought is somewhere in the middle of these circles. In an urban setting the circles would be small (a few hundred meters), in a rural area the circles would be bigger.
As stated before, it’s not an exact science. When GPS data is available that is preferable to use. But in those rare cases when it is not, this approximation can mean the difference between a person being in one place, when they say they are in another. A phone’s location can be narrowed down to within 100 meters or less.
ABOUT THE AUTHOR: Scott Greene of Evidence Solutions, Inc.
For over 30 years, Scott Greene of Evidence Solutions, Inc. has been helping companies meet the challenges of the swiftly evolving computer technology industry. Scott went to work for IBM. Scott studied Systems Engineering at the University of Arizona. He has since earned certifications in many products and programming languages.
The Evidence Solutions team analyzes data from Computers, Cell Phones, Black Boxes, Dispatch Systems, Medical Records, Email systems and more. Scott then explains the digital evidence in plain English.
Scott’s extensive knowledge draws clients to him from all over the United States as well as Internationally for consulting, Forensics and expert witness services. His extensive and diverse experience allows him to be an expert in many facets of digital and electronic evidence. Scott, a sought after speaker and educator, travels throughout the country sharing his knowledge and presenting to local, regional, national and International organizations.
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Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.For specific technical or legal advice on the information provided and related topics, please contact the author.
