November 30, 2005

Airspace Files

Worked out some glitches on getting the airspace files stored in the right directory / file for Flightgear to display the circular cores of B, C, and D class airspace. I'm only using an 8 sided cylinder for the circles at this point. Next, I'll work on routines to get the circular arcs and line segments in that make up the gerrymandering of the overal. airspace system.

The first shot is coming from Burlington, VT towards Lebanon, NH. Lebanon is 50 nautical miles off, and the blue band on the horizon is Lebanon's Class D airspace circle of 4.8 miles radius. The second shot is from the Manchester NH airport area toward Boston with Boston's inner and outer circular core of Class B airspace depicted. This is the classic upside down wedding cake airspace structure with a central core to the ground surrounded by an other shelf. There is a lot more complexity to the airspace system to put in, but this is a pretty interesting start. Generation of the airspace files is automated using the Defense Mapping Agency's DAFIFT data files to put together the airspace system into a flightgear compatable format. What a hoot!

As a low-time pilot, I always have a heck of a time pinpointing runways from far off and it sure will be nice to spot some by there airspace. Next, I want to see if I can modify the companion Atlas moving map software to display the airspace perimeter outlines, ala the way Klog does.

November 26, 2005

Class D Air

So far I have managed to automate generating files for displaying the circlular core of airspace around class D airfields. Here is Lebanon in a reverse contrast image and the conventional summer terrain texturing native to Flightgear. My old 2nd seat in the legislator, also an A/P, Phil Weber, came by over the holidays from Pennsylvania.

I have also finally gotten around to doing a rewrite of my website to put some of the synthetic vision material on there, including the sources for the revised hud and code to interface with the Crossbow uNAV device. I also have been looking into getting a mini-ATX computer board to make the synthetic vision system portable so I can run some field tests... But, it turns out the graphic accelerator cards are power hungry and I haven't found an mini-ATZ with a power supply big enough to support the graphics card. If I had my choice, I would go with a Panasonic ruggedized laptop, the ones with the sunlight readable display, but at $3500 clams, that's a bit much.

Now, back to burrowing into the DAFIFT database. This is the same database, by the way, the defense mapping agency claims to want to take out of the public domain and make secret? I'm still curious as to what the hell the big secret is as to the boundaries of airspace already depicted on sectional maps! This sounds more like an effort to force people to get their data from some congressional chairman's pet defense contractor... For a fee. Come to think of it, one of those folks just got clipped in Kalifornia for being ye olde bribe bait.

November 18, 2005

Predatory Visit

Have been working on automating decoding the defense mapping agency's DAFIFT database for airspace boundaries so I can display them in the synthetic image. Friday, two weeks ago, I was working away at the computer when up pops papa fox for a visit. As expected, he snooped his way around the corner to the (closed) chicken coop. Sorry pal, no chicken din-din today. This fella was pretty big, first time I've seen one with a white tipped tail.

November 17, 2005

Catching Up

Couldn't resist trying out a crude adaptation of a logitech joystick to the control stick on the plane. Mickey mouse, but it works if you hold it down with one hand. Serously though, it was a nice excercise to see what kind of ergonomic nightmares/opportunites are associated with a keyboard in the cockpit. Definitely needs some tuning, but it turns out the logitech joystick controller probably is doable to track stick status at the cost of a usb port. The controller will interface to regular ports so the next step will be to machine up some bracketing to hold the resister and linkage to the stick.

November 13, 2005

Sunday Flying

Sure got a tad hazy Sunday, but I wanted to get up anyway as I haven't flown since July 3rd. Was a bit rusty on the currency take offs and landings before taking Cathy and her mom up for some hazy sightseeing out towards Mt. Ascutney and Hawks' peak, the site of the 1947 B-29 wreck. The haze did not make for a perfect picture taking day. Here's a shot of the approach to 18 at Lebanon and a flightgear rendering of approximately the same position. Now, if I can scrounge up a laptop with an accelerated graphics board, I can get flightgear and the sensor running in an a portable unit.

For now, I'm still driving flight gear around to position the viewpoint and comparing them to photographs of the area. I'm pretty confident now that I can get the synthetic vision to work with Crossbow's certificied sensors in addition to their uNAV sensor... It is my understanding crossbow supplies the inertial device for the Chelton system. I also note that if other simulation software such as x-plane, or even (bannish the thought) microsoft publish an interface and support a documented socket programming protocol you could using sensors like the uNAV with a small programming translator to drive other simulation displays. A secondary issue arrises as to the pedigree of the terrain database(s) used by the flight sim, but that class of problem sure beats creating the display software from scratch!

November 08, 2005

From Canaan

I finally got my sensor talking to Flightgear in real time via socket programming. If you're willing to thrash around for a while you can learn to do just about anything by studying source codes. It turned out I only had to tweak the uNav/Stargate published source codes a bit and run Flightgear on the TCP protocol (until I figure out how to shift to others? ...If it matters). First you make things work, then you make them elegant!

The output jitters a bit with about (1) degree of variation over time in heading position. I think this may be a calibration issue, but it will a while before I burrow into things and check that out. I may be getting effects from the fact that the sensor is in a cardboard box on top of the Linux box. Of course, for an extra $10,000 to $15,000 you can get a sensor that doesn't jitter... Anyhow, the uNav definitely is sensitive to iron as readily illustrated by moving a small screw driver near the device. I think I swung the compass (and the display depiction) about 15 to 20 degrees with the screwdriver. I wanted to take the picture of the device next to the monitor but nixed the idea because of the steel used in the support frame the monitor sits on. Plus I figured it probably wasn't a great ideat to get it anywhere near a flyback transformer...

Progress only cost me two lock-ups of my machine and I have some file system cleanup to do from the wreckage, but it is nice to verify that you can combine an inertial sensor with a flight simulation package and produce a sophisticated cockpit display capability.

Meanwhile, back at the ranch... Joel Godston (retired from Pratt & Whitney) gave a talk on jet engines this evening at our EAA chapter meeting. Joel brought parts! ...From his development days when they tested engines, and that occasionally meant frying them... When you think of it, the development of gas turbines over the last 50+ years has produced the most reliable and fuel efficient high output engines ever produced.

November 02, 2005

Synth Vision

OK, so it takes a little spit chewing gum and bailing wire... But HOT DIGGITY DOG - It works! I have my uNAV sensor from Crossbow talking to my Linux box which runs the Kalman filtering algorithm stuff to output honest to goodness inertial data. I currently have the software writting a binary file in a Flightgear compatible format; then I feed the file into Flightgear to play it back and voila - the view from the house (which isn't all that interesting) so we artificially modified the altitude by adding 500 meters and presto... For your viewing enjoyment: The view from about 1500 feet above the house... And this is all with off the shelf technology!

Now, to get all this stuff working in a mobile package...