Additional notes on constraints

1. I love learning new technologies, especially in the context of a personal project, because under no other circumstance does a technology present itself so openly. At least, that's been my experience. For instance, I'm going to try and do a lot of the coding here in Python because:
   1. NodeBox, which I already mentioned
   2. I've been wanting an excuse to learn it
   3. this project feels like the right mix of light coding and quick development that I've heard lends itself to Python. It's also not doing anything super-fancy from a software perspective, so I won't be hitting my head on the language quirks right away.


2. I like to use open source software whenever I can. In addition to the financial benefits (yay free stuff), I like the philosophy of community driven software, especially for oddball projects like this one. :-)

Constraints

As I mentioned briefly in the first post, this task is not as trivial as it might at first seem. There are a number of constraints on the project:

1. Cost: Doing this in my spare time and not having a desire to shell out for hardware that would have little use in other projects, I'm looking to use off-the shelf general purpose hardware as much as possible, while keeping the costs down.
   Current thoughts: This constraint comes into play on all subsequent constraints.


2. Stabilizing: Our first thought when designing the coasterometer in our heads was to mount all the sensing equipment (camera and accelerometers) in a helmet and perhaps run cables down to a fanny pack or pocket to record the data. This base design was inspired largely by the easy availability of camera helmet-mounts for skydivers. However, on a typical roller coaster ride, the head is apt to move around quite a bit, which would skew the accelerometer data and the imagery.
   Current thoughts: Mount the accelerometers near the chest, since most coaster restraints cross either the hips or the shoulders, leaving the area around the sternum clear.


3. Size: Most amusement parks don't look kindly on folks trying to bring unattached items on the ride. A large sensor-bearing helmet would likely be frowned upon by the ride operator. So all of the equipment has to be small enough that it can fit underneath a person's clothing without making them so bulky that a ride restraint would fail to operate.
   Current thoughts: Essentially make this a wearable-computing application, and distribute as much as possible through the body so as to keep overall profile slim.


4. Data Recording: There are two sets of data being recorded on any one ride: the three-dimensional readout of the accelerometer, and the video feed from the camera. I had initially considered using a Phidgets accelerometer, having used Phidgets sensors on a previous project and thus being familiar with their programming interface. Unfortunately, Phidgets hardware requires a USB host port on its attached computer -- a USB host port is what is probably on your computer, a USB plug that allows your computer to communicate with other devices. Unfortunately, most computers small enough to conceal under clothing only have a USB device port -- they can only communicate with a real computer, not other devices. Tiny portables with USB host ports exist, but as of 2006 they are prohibitively expensive for the purposes of this project.
   Current thoughts: I ultimately discovered Spark Fun Electronics, who make a wide variety of sensors that can communicate over good ole serial connection. This discovery of serial sensors with an easy software interface allowed me to pursue a much more affordable recording device.


5. Computing Device: It has to be small enough to conceal, powerful enough to be easily programmable, and affordable enough for me to get one. I've currently settled on using a Sharp Zaurus 5500; it's an older device, which is why I was able to buy one for ~$50 off a friend. It runs Linux, which means a decently sized community has grown up around it to support development. The MIThril project at MIT uses a Zaurus for their applications, so I figure it should do the trick.
   Current thoughts: The Zaurus is currently the only component I currently have in my possession; hopefully it will work out. Otherwise it's back to the drawing board.
   Note: It has been suggested that I could reduce costs and complexity by creating a custom circuit with an accelerometer chip, a microcontroller, and an EEPROM to record the data. Unfortunately, I know little-to-nothing of electronics and circuits, and need a software interface. I'm always interested in learning something new, though, and am considering a custom circuit if I ever make a second version of the coasterometer.


6. Video Recording: There are two problems here.
   
   1. The first is camera placement -- I can't very well strap a camcorder to my head and keep it concealed.
      Current thoughts: Use a tiny camera along the lines of a micro board cam and conceal it behind a shirt button. This allows it to be mounted in the sternum, right near the accelerometer, so clutter and cables can be reduced in the final design.
   
   
   2. The second issue is the camera itself. I want to use a MiniDV camera so I can easily edit the footage later on a computer, but I need to be sure the camera has analog input capability so it can interface with the tiny camera. Sadly, not all cameras have this ability any more, and trying to figure out which ones do is a tricky proposition.
      Current thoughts: More research is required in this area. I would like to have a camcorder anyway, so the cost of this purchase is not considered a "project expense" per se. At the same time, I want to exercise the same careful, researched buying habits I have with all my electronics.
   
   
   
   
7. Wearables: Ultimately all of these devices will need to be mounted on my body, and the camera and computer both need to be accessible so I can turn them on at the start of the ride. Where exactly they should go is one question, but the other is how to keep them there?
   Current thoughts: Need to find some kind of tight-fitting, stiff vest for the tiny camera and accelerometer; either that or some good way of securely strapping something to my chest that doesn't involve duct tape and pain. I'm thinking of putting the Zaurus on my thigh, with a flap cut in a cargo pocket to allow access. How it stays there is still a question. And then where the heck should the camera go?


8. Data Processing: At the end of a run through a roller coaster, all I'll have from the accelerometer is a whole bunch of numbers. To work them into something meaningful, I'll need to do some post-processing and generate a visualization of the forces experienced on the ride.
   Current thoughts: I recently discovered NodeBox, a Python-scriptable image generation toolkit for Mac OS X. It looks like it has great-looking output. Unfortunately, my knowledge of Python is minimal at best, but what better time to learn? I'm a little concerned about limiting the portability of the data processing code, but if NodeBox proves to be too big a hammer for the task, I can always just make a generic ImageMagick script anyway.


9. Video Editing: After I have the beautiful output detailed above, I would like to overlay it on the first-person video from the ride, so someone watching can get a sense of the forces they would experience while seeing the coaster move around the track. I could do this with custom software, but it seems like more trouble than it's worth, and I want to edit the video anyway. I know there are simple video editors out there, but after working with real editors like Final Cut and Avid while I was getting my master's degree, I can't go back to simple editing. Unfortunately, I'm no longer a student and can't afford to shell out for Final Cut Pro at this point, nor do I own a Mac capable of running it well.
   Current thoughts: I do, however, have a pretty powerful PC (have to keep up with the industry for my day job), and have heard decent things about Cinelerra, an open source high-end video editing system. I'm still having some trouble getting it running on my Ubuntu install, but that phase of the project is a ways off yet.

Whew! I think that pretty much covers the set of constraints for this project. It's not an easy nut to crack, and I would certainly appreciate advice on any of the points. In particular, at the moment, I'm most worried about how to secure the devices to my body, but all of these constraints are difficult problems on their own.

How it all began

At my alma mater, the end of finals and graduation are separated by a week. A large portion of the population (though I hesitate to say a majority) spends this week at one of several beaches along the Atlantic coast in a tradition called, imaginatively enough, "Beach Week."

I went to Beach Week after my first year, but found it to be not quite my cup of tea. Having spent my formative years at another beach, I wasn't quite as gung-ho for the sandy brine as my classmates. The next year I joined a few of my friends on their long-standing tradition of "Alternative Beach Week." These wise folks spent the intervening time period riding roller coasters and (the year I joined, and most years since) seeing the movie premieres that typically abound during that early portion of the summer. Now this was something I could get excited about.

One year, while waiting in line, we got into the age-old (among coaster enthusiasts at least) debate as to whether the front, back, or middle of the train provided the so-called "best ride." While the quality of a ride is purely subjective (some people not enjoying bumps, others relishing them), we could not even come to an agreement as to where the forces of a ride would be the greatest. This was most bothersome, especially since our group is composed heavily of engineers.

So we created, in our minds, an apparatus that could measure the experience of riding on a roller coaster. It would contain accelerometers to measure the forces and a video camera to record the visuals. It sounded fairly simple.

It actually is not.

While it seems most of my group has since lost interest in such a project, I find myself now both gainfully employed and with a modicum of free time. And I still love roller coasters. Thus you have the Coaster Metrics Project. In this blog, I will be recording my efforts to build the measuring device (coasterometer?) and the results of my visits to roller coasters with the equipment.

Hopefully it will be interesting to someone.