[time-nuts] Lightsquared and a little math

Bob Camp lists at rtty.us
Wed Feb 2 17:57:33 UTC 2011


Hi

Let's see, a 13 mile circle is pi r squared = ~ 530 square miles. 
40,000 times 530 is ~ 21 million square miles. 
Wikipedia tells me that the area of the US is 3.79 million square miles.

On that basis, there's not going to be anywhere in the US that you *can* get
GPS to fly a plane. Jamming detected = could be a problem = you can't trust
it.

I suspect that there indeed will be remote parts of Alaska or the like that
you will indeed still have un-jammed coverage in a plane. 

Now for the "best case":

5.6 miles loss of fix = just under 100 square miles. That's 3.94 million
square miles of jamming. That's still greater than the area of the US. I'm
sure we'll have some left over to jam Canada and Mexico as well. Again,
there will be patches where you can get a fix, but they will be the
exception rather than the rule. 

File an IFR flight plan based on any of this - no way. Insure an airline
that does that - no way. Run an airline based on "VFR only" not going to
happen. Is everything GPS based - no, but there's a lot of the country where
it is.

Not at all clear how you will keep aviation going under those conditions
unless Lightsquared replaces all their gear with *type accepted*
replacements. Where do I sign up for my free gps? 

Let's suppose they have big pockets and do all that.

At the consumer level, you have 128 thousand square miles with urban canyon
issues. Good bet that's every place with an urban canyon in the country.
Essentially cross off GPS in every large city.

Out here in the sticks, things are a little better. Only a bit over 17
thousand square miles lost. Except ... do you have any hills or mountains
near you? Back to the paragraph above if you live anywhere other than
western Kansas.  

Why are they setting this up - to get internet to people. Where are the
transmitters going - where people live. The consumer numbers may not sound
as bad, but there's a lot of country that is pretty empty. Look at any cell
coverage map to get a good idea how much. You still nuke a lot of voters
with "only" 17 thousand square miles. Not to mention fire, police, EMS, and
the DHL guy. 

Then you have the federal law about 911 tracking on cell phones. How does
that work - GPS. Under what conditions - worse than an urban canyon (no sky
at all). You *at least* have the urban canyon area to deal with and likely
worse. Any bet your cell phone GPS is as RF rugged as the one in your car?
I'm not taking that bet. Bop up the coverage area a bit more.

So average urban canyon with airborne and what do you get - just a bit over
a half million square miles. My guess is that's the whole area of the
country that has a population dimensioned in multiple people per square
mile. 

So we have:

1) Multiple Airplanes running into mountains
2) Many houses burning to the ground
3) Lots of 911 calls getting miss directed and people dying as a result
4) Joe six pack getting lost on the way to the beer store

All could be what nukes this. I'm betting on number 4 ...

Bob





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