Posts by Robert Woodhead

Jules Verne creeps up on ISS

GPS basic facts

GPS constellation altitude is 20,200km. This is below geosyncronous orbit level; in fact, GPS sats make exactly 2 orbits a day. Furthermore, they are in highly inclined orbits, as opposed to communications satellites, which are in equatorial orbits.

GPS sats beam their signals in fairly tight beams down to the earth's surface (for efficiency purposes), but there is enough spillover that it can be used without problems in low earth orbit. The major modification that is needed to a standard GPS unit to work on the ISS is to remove the "sanity checking" code in the GPS ("gee, I'm several hundred kilometers high, and moving along at over 10,000km/hr. I must be broken!").

Ham radio enthusiasts put a GPS in one of their recent "Oscar" amateur satellites. They found it was even possible to get GPS to work above the level of the constellation, there is enough leakage of signal outwards (and you can detect GPS signals from sats near the edge of the earth) to get good readings.

With a decent antenna, you could get GPS to work on the moon -- well, the parts facing the earth, anyway.

Sweet, sweet smell of comments in code?

Comments are Literary Expression

I've been programming so long that I don't write code anymore, I just remember it and type it in again... So from that perspective:

Comments serve several purposes:

1) To explain what the code does.

2) Ummm.... no, to explain what you EXPECT the code ought to do, in a perfect world.

3) To remind you (and others) about what you were thinking about when you wrote the code.

4) To brag (even if just to yourself) about a particularly nifty bit of code, and to pass on that slelegant (sleazy & elegant) hack unto the next generation.

5) To explain (or make excuses for) why you perpetrated some abomination or another. There was a good reason, honest!

6) To provide clues to the poor bastard who will take your place after your fatal encounter with the BOFH.

With respect to the last of these items, one should always take a little extra time to make one's comments literate and entertaining. The poor bastard who comes after you (heck, it may be you 5 years down the line) will be suffering enough, anything you can do to reduce the pain will be appreciated. At the very least, it will reduce the number of times someone visits your grave to piss on it.

Those who claim that good code does not need commenting should be sentenced to have to rewrite some of their own 15-year old code in a different language and operating system... oh wait, that's silly... they haven't been programming long enough for that!

Is an artificial eye close to reality?

The Blind Seeing Colors scam

This is an old trick.

First of all, since they are putting a blindfold on the woman, she's probably legally blind but not totally blind.

Second, unless the blindfold is put on by someone who knows what they're doing, she's probably seeing the color by looking down her nose - this is how almost all the people doing this trick do it.

Finally, if she really can do this under proper scientific conditions (in other words, with some real magicians around to make sure they aren't being fooled), The Amazing Randi (www.randi.org) has $1,000,000.00 to give to her.

http://www.randi.org/jr/021502.html and http://www.randi.org/jr/022202.html contain a two-part article about a girl who claimed she could do this, and how the trick is done.