The forecast: partially cloudy with a chance of... satellites

Gotta love science... In an effort to be completely meticulous about every possible source of systematic error that might creep into our positioning system, we have incorporated tropospheric corrections into our GPS satellite signal interpretation code.

What's the troposphere? Well, the big bubble of gas and crap floating around the Earth (held there by its gravity, by the way) can be divided up into a couple of different layers. The troposphere is the lowest of these layers, and it's made up mostly of air and a little water. Next comes the stratosphere, and finally the ionosphere, stuffed full of weird plasma and other charged things. A GPS signal originating from a satellite and going on its merry way toward our receiver needs to pass through all three of these atmospheric layers, and of course, it would be far too easy for this signal just to pass right through unaffected. No, instead it's curved and bent up in a very sensibly-nonsensical way, and if you don't account for that, then your computed position will be wrong. So what do we do?

We turn our position estimator into a weather station, that's what we do. Yes that's right, our position now depends on barometric surface pressure, ambient temperature, and relative humidity. If it rains, we want to know about it.

Sheesh, I feel like a weatherman. I swear at some point I was actually a Mechanical Engineer, honest!

So... it's definitely been a month and a half.

In this case, lack of news means good news. Since we visited the participants' conference, we wrote and submitted a DARPA contract proposal for the Urban Challenge. We've thought out all the critical parts of our solution, wrote them all down, and sent them off to the powers that be. I expect everybody to keep their fingers crossed.

Today we also got our first major win for the season: a sponsorship from Septentrio. Septentrio is a Belgian company that makes what are arguably the best and most robust GPS receivers in the world. Details are still in the works, but I'm hopeful that they'll let us use their tri-antenna single-clock receiver:

What makes it so good? In this case, more antennas is better. It means that we can track the same GPS satellites with multiple antennas, which helps us figure out where we are and where we're pointed more accurately. All three antennas are operated off the same clock as well, which reduces the amount of error in the system.

Now about getting those free cars...