[time-nuts] Lightsquared and a little math

Pete Lancashire pete at petelancashire.com
Wed Feb 2 18:12:50 UTC 2011


Go back to my orig post the FCC has given the go ahead .. to late ?

On Wed, Feb 2, 2011 at 9:57 AM, Bob Camp <lists at rtty.us> wrote:
> 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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