Sunday, December 23, 2007

The Marauder's Map of Olin

A friend and I have been planning this for a few months. On a laptop, we can find the signal strengths of wireless access points, and use this information to determine location. A few days ago, I sat down and coded it, in time for Expo. My poster probably says it best:

Instead of using triangulation, it simply acquires a lot of data. (Triangulation did not work as well, because of the many walls and windows in our dorm.) The database simply records associations of a set of wireless signals with a name ("AC Room 318") and a point on a map. To look up a position, the server looks for a similar set of values with a distance formula, and returns the closest match. When the program is run, it recieves feedback from users, and every time adds a new association. Over time, the results get better and better. From successful tests, I think room-level precision may be possible.

We were able to figure out the right WMI query to find signal strengths other than the current connection (in Windows). I then wrote a small C# app that runs the query and prints the results to stdout.

A Python program gathers this data, taking the average of three runs, and sends it to the server. A PHP script forms a vector, thinking of each of the 76 access points as an axis, and looks for nearby vectors in the database. The location of the user, and status, is also stored in a centralized database.

Finally, in a web app you can view locations of everyone who is logged in. Hovering over the icons tells you who and where the person is. (Only if you swear that if you are up to no good).

Monday, December 10, 2007


I'm in ProbStat this semester. I didn't feel like working so I wrote a quick little program.

Tools like SurfStat are nice, but they aren't quite what I want. So, I wrote a similar web app, Improbability. You can tab through the fields more easily and simply press Return to evaluate. Also, there is a graphical display of the area under the curve (using CSS and transparency).

So far, just the normal distribution until I'm satisfied with the interface, but other distributions will be pretty easy to add. I just wrote this, and am open to suggestions as to making it better.

Friday, December 7, 2007

Math Console

Here's my old Math Console.

Before I had ever used Matlab, I wrote something resembling it (in JavaScript, of all things). I used it at the time for my statistics class, and kept the code kicking around, but never got around to finishing everything that I had planned. (I had wanted to add many more statistics features). One of the factors was JavaScript's lack of support for overloading operators, which kind of stopped things. Also, there isn't really a convenient way to support complex numbers.

Today I made it (somewhat) cross-platform. Since this might be as complete as it will get, I'll call this the last version. Open the page and you can click a link to see a list of features and provided functions.

I still think this is a pretty cool project, and I am just now working on something similar in Python.