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Military Tech: GPS and Networking
king of birds writes "The New York Times has an interesting article on the present military use of GPS. While some units have rather modern system that can graphically display locations of other troops, others rely on 10-year-old 5 channel receivers. Kind of odd when I can 12 channels on my civilian model (with admittedly lower spatial accuracy)." aaronvegh writes "From the Canadian Press, a story about how a US infantry division uses a system of transponders and servers to track friendly and enemy units, from the headquarters to inside individual tanks. Talk about total information awareness! No friendlies were harmed in the making of this story."
It just tells you exactly where you are lost.
Kind of odd when I can 12 channels on my civilian model
Of course, your civilian model probably fails 1% of the time, and wouldn't survive a day in a sandstorm, in part due to it's fragile electronics.
The Military version, while only 5 channels, is probably much more robust then your puny little civilian model.
When all you have is a hammer, everything looks like a skull.
WW II: 21,000 (16%)
Vietnam war: 8,000 (14%)
Gulf War: 35 (23%)
Afghanistan (2002): 4 (13%)
The difference today is instant communications. And the small number of total casualties allows the media to focus on each death.
Many military radios can do frequency hopping - changing frequencies many times a second. So unless you have a similar device AND you know the algorithm, AND you know the starting frequency, AND you know when the radios were turned on...
Come on, I know someone works in a Comm MOS and can 'splain it better ;-)
A pilot, in those days, was the only unfettered and entirely independent human being that lived in the earth.-Mark Twain
Many military radios can do frequency hopping - changing frequencies many times a second. So unless you have a similar device AND you know the algorithm, AND you know the starting frequency, AND you know when the radios were turned on...
I use to work on military communications. The version I worked on switched frequencies about 10,000 times a second. That was ten years ago. Not only is this harder to track, but even more importantly it's harder to jam. Keys were changed daily.
Isn't it a little risky to put location transponders on all your military units? If the enemy cracks your transponder codes, they can easily target you.
Similar concerns can be raised about almost any military technology or activity. Don't use radio - the enemy might hear what you say! Don't use radar - the enemy will know where you are! Don't open fire - you will reveal your position!
Military winners are willing to take such risks in pursuing their objectives. They know that being aware of the situation and acting proactivly and agressively is more important than never revealing anything to the enemy. There are of course circumstances where one should be stealthy, but wars are not won by armies remaining completely hidden in cover.
Tor
From the article:
The new system will also track all 12 G.P.S. satellites in each hemisphere at once. The old units can only track five satellites at once, and signals from four satellites are required to establish a three-dimensional position. In addition, current G.P.S. receivers are somewhat vulnerable to enemy equipment that beams false G.P.S. signals to indicate the wrong location, a technique known as spoofing.
Here's the thing: the article is correct about the PLGR needing four locked satellites to establish a three-dimensional position. However, a PLGR can also establish a two-dimensional position with two locked signals and one intermittent one. The important part here is that the PLGR's most common use (determining position for individual soldiers and vehicles) doesn't need a 3D position. Your position (including elevation) can be plotted on any map using only two coordinates. 3D positions are only important for aircraft, air defense, and artillery. And for the most part, those guys aren't using PLGRs. Oh, and PLGRs can track up to 10 satellites.
This corrective post brought to you by a US Army Cavalry Scout. (None of this information, by the way, is classified or restricted. The reporter just didn't check sources very well.)
Arr! The laws of physics be a harsh mistress!
While some units have rather modern system that can graphically display locations of other troops, others rely on 10-year-old 5 channel receivers. Kind of odd when I can 12 channels on my civilian model (with admittedly lower spatial accuracy).
The fact that some units are using a "10-year-old 5 channel receiver" does not surprise or concern me in the least. The military has prerogatives other than "latest and greatest nifty stuff" when procuring equipment.
Those old units probably contain custom hardware to cope with un-obfuscating GPS signals for back when the signal was still (and could again) being obfuscated. Those devices survive generation after generation of soldiers who are expected to use the things in all combat environments. In other words, this is not some plastic Taiwanese el-cheapo GPS receiver you paid $300 for at wiggliesneatshit.com. Do you have any clue how much time and money it takes to build one-off mil-spec equipment in low volumes that the military routinely requires?
I've actually found detailed technical information about the unit you're talking about. It's here and it's a damned interesting read. For instance, does your spiffy little 12 channel unit happen to have any anti-jamming/spoofing features? Exactly how many artillery shell concussion shock waves will your unit survive while your crew is firing the ol' 155mm? The DoD is so happy with the things they are trying to extend the warranty!
The fact that some units have more modern equipment than others is a perfectly normal, healthy way to run a military. Some of you paying attention to our recent deployment to Iraq have learned that the Army's 4th Infantry Division has only just now arrived in theater. This happens to be the Army's "showcase" Division. If it's the latest, the 4th ID has got it. It's not that our government didn't want to deploy the 4th, but Turkey didn't cooperate and the whole outfit had to be floated around the Mediterranean. Basically, the most advanced ground force on Earth arrived just in time to become traffic cops. Meanwhile, the old fashioned 10-year-old PLGR units are probably exactly what the 3rd ID used to actually get the job done.
You show me someone astonished by military procurement practices and I'll show you an ignorant fool. The next time you have the urge to compare your knowledge of equipment/technology to that of a military, just assume your wrong and shut up.
Maw! Fire up the karma burner!
Slow? resource intensive?
GPS uses triangulation, essentially, although it's a lot easier since it sends out a timestamp. To triangulate a unit, you would have to have 3 stations be time-synchronized and all would have to know they heard the same signal -- which is undoubtedly coded making it EASIER to know it was the same.
In other words, tank A sends out an encrypted digital message of "here is my location". If 3 stations hear the signal and timestamp it to the nanosecond, they can them compare the signal--without knowing what it actually broadcast--and tell it was the same broadcast. Using the time data and and the exact location of each station, it's a simple matter to plot the location of the transmission. The farther apart the 3 stations, the better the accuracy. More stations would lead to more accuracy, plus you'd couldn't shut it down by bombing a single tower as long as 3 remained.
This would essentially be a reverse-gps. It's only resource-intensive and slow if you have a single unit driving around with a directional antenna, like the FCC did to locate pirate stations. If you can synchronize the clocks and timestamp signals accurately, it's almost trivial to pinpoint the location.