title: Calculating distance of an AP including signal-to-noise ratio
body: <p>For some reason a friend and myself were talking about calculating the distance between yourself (laptop, phone, etc.) and an AP based of the info you get from the devices (RSSI, freq, SNR, etc...).  So, after spending sometime researching about trilateration, triangulation, and free-space path loss. (with the help of some blog posts and wiki) I was able to get a distance in meters from the AP to my laptop and the results were a lot better then what I thought they would be. Whenever I'm in the same room or there's a line of sight to the AP, the accuracy is about a foot.</p>
  
  <p>But now, I want to take it one step further... I want to be able to account for walls and other obstructions. I think this might be possible or at least give me a better results then the FSPL formula when there is obstructions and I was thinking/researched that it might be possible by calculating in the signal-to-noise ratio. But, I was unable to find anything on how to do this correctly. There was always a problem but never a solution to this idea (or I was unable to find anything on the web because my knowledge about this subject is very little. about a days worth.). So, here I am turning to stack overflow to see if you guys can help me out in solving this.</p>
  
  <p>So, this is what I have so far (in python)....</p>
  
  <pre><code>import math
  
  freqInMHz = 2462
  levelInDb = -83
  SNR = -87
  
  result = (27.55 - (20 * math.log10(freqInMHz)) + math.fabs(levelInDb)) / 20.0
  meters = math.pow(10, result)
  
  feet = meters * 3.2808
  
  print meters
  print feet
  </code></pre>
  
  <p>I am from the US, so I printed both meters and feet out. Just because I can visually measure out feet better than I can meters.</p>
  
  <p>So, with that formula it does a great job of finding the distance in an open room or clear view of the AP. If anyone has any ideas or comments I would greatly appreciate it. Because I'm currently stuck on a wall! (joke punch line drums sound) </p>
  
  <p>Thanks,
  Throdne</p>