On Fri, 19 Dec 2003 05:54:28 +0000, phil hunt wrote:
On Thu, 18 Dec 2003 20:53:21 GMT, Kevin Brooks wrote:

"The programming for this isn't particularly hard"?

Read the rest of the sentence: "...once you've written software
that can identify a vehicle (or other target) in a picture"

I could probably have phrased that better.

Like, say, "The programming for this isn't particularly hard,
once you've waved your hands and assumed all the really hard
bits are already done"?

[...]

You have a rather optimistic view of the capabilities of most nations to
handle development of truly accurate x-y-z topo data sets. And once you do
have that data, you have to have a guidance system that can read it, remain
compact enough to fit in your missile,

You do realise, you can get hard disks small enought otfit in your
hand, that store tens of gigabytes these days?

Of course you can. Just because you have somewhere to put the
data doesn't mean the data is easy to acquire, though.

You can get detailed digital elevation data for the United States
(horizontal resolution of 30 meters for the lower 48, 90 meters
for Alaska), but that's because the United States Geological Survey
has gone to a great deal of effort to compile it and make it
available.

How many other countries have done the same? Does the
Royal Elbonian Survey Office even have decent 1:24,000
topographic map coverage of Elbonia to use as a starting
point for compiling a digital elevation model?

[...]
Your LORAN system bites the dust when the curtain goes up.

No, because you use multiple transmitters, which aren't all switched
on at once, plus large numbers of fake transmitters there to be
targets for bombs.

LORAN transmitter sites are not small. Check out

http://www.megapulse.com/lorsys.html

for a picture of a modern solid-state transmitter -- they
don't need water cooling systems any more, apparently, but
you still need a large room with a HVAC system capable of
handling "moderate air-conditioning loads".

That's nothing compared to the size of the antennas, though.
A LORAN transmitter station typically has multiple guyed
antenna masts with heights ranging between 300 and 1,000 feet.

You are not going to be able to build lots of them,
and you definitely can't move them around.

The transmitters can shift frequencies and use
short transmissions, to further reduce the probability of being
detected.

Great -- now all you need to do is figure out how to
hide a forest of immobile antenna masts that are hundreds
of feet tall.

Automated celestial tracking/guidance is not the purview
of the amateur, and I doubt you would get the requisite
accuracy from such a system mounted on such a
small platform.

Why is the platform size an issue?

You need a stable platform for accurate celestial navigation.
A small aircraft-sized HLCCM isn't it, and semi-accurate celestial
navigation only tells you your position to within 5-10 miles.

You also need to be able to see the stars, so using celestial
navigation would mean your HLCCM would only be able to navigate
to its target if it was night and the weather was clear.

Automated celestial navigation is really only practical for
vehicles that operate outside the Earth's atmosphere --
spacecraft and ICBMs.

DR is a non-starter--again, you don't just hurl a few
missiles in the general direction of the bad guys and
say, "Gee, that was tough--time for a beer!"

Again, why would DR not work?

Because dead reckoning is the least accurate form of
navigation. Do you really want your HLCCMs to miss
their targets by miles because the wind changed
direction after they were launched?


ljd