He gives a very nice spectrum on slide 4 -- note the little bump at the bottom labeled "Starfire/Omnistar" -- that's the correction signal used by the John Deere precision GPS system, and others, broadcast by Inmarsat III. It's f*ing buried under the proposed LightSquared 10H signal at 1550.2, and still under the skirts of their 10L signal at 1531!
Yup, that has a nice picture illustrating the problem.
ANYTHING carried by Inmarsat III in that band just below GPS L1 is so screwed if LightSquared uses those frequencies!
this is also a pretty clear indication that FCC was bought off at a high level, and their technical types didn't get to look at it -- they would have screamed.
Yes, that seems to be happening a lot lately. Good, bottom-up technical analysis from FCC engineers get overridden by political concerns. Broadband over Power Lines (BPL) is another egregious example of politics forcing idiotic technical decisions. Spectrum sharing compatibility analysis seems to have been left back in the last millennium some how.
OK, I quickly looked over the excellent presentation that you link to. I don't see where it shows a GPS precision-enhancing signal in L-band getting swamped. It *does* show 15 kW (!) terrestrial base stations very near the GPS L1 band having the potential to get past the roofing filter in a GPS, as my previous post was attempting to yak about.
I was under the impression that differential GPS used short-range terrestrial VHF for a localization signal from another GPS receiver looking at the normal GPS signal -- is my understanding stale? Has something new come along when I wasn't looking?
But holey schmoley, 15KW at 1.5 GHZ? That's manly. That takes a moderate amount of effort. It also raises some RF safety issues -- what kind of antennas are they using with this? What is the EIRP?
Anyway, for whatever reason, my previous post has been generously modded "+5 insightful" at the moment, when it's really just speculation based on "here's how radios work in general"... I'm not a GPS expert. "+/-? Plausible BS" is probably a more accurate mod score.
It's very unlikely to be lightspeed signal bleeding over out of their channel. That is reasonably easy to control, and it would show up in 100% of tested receivers. More likely, this is "adjacent channel interference". It is much harder to get a receiver to reject signals in adjacent channels. It takes a difficult/expensive to construct filter. If you go back to the old days of television, you'll note that you don't find adjacent channels allocated in major markets, for instance, because in the early days it was essentially impossible to build a receiver that could reject a strong signal on an adjacent channel. So here we have a case of a receiver looking for a very weak signal, and on an adjacent channel there is a strong local transmitter that you are trying to reject. I'm no surprised that there are issues. Also, because GPS has up till now not had strong nearby, adjacent signals to reject, it could actually be that the first mixer is getting overloaded, so the damage is done before you even get to the first IF filter.
Continuing in the tradition of Forth programmers everywhere to define new words and compress the code until the entire application fits on one line, and is indistinguishable from modem noise:
Forth-sightful 1+
the word '1+' (or a variant) is often defined because incrementing the top of stack is so useful. And if you want to see the result:
Forth-sightful 1+ .
Forth has its place, but I'd hate to implement anything big using it.
In principal, I'm OK with some form of metered usage. But I don't want to pay for the bandwidth associated with advertising -- if all I want out of a page is the 2K of text that dispenses useful information, I don't want to pay for downloading all the Flash ads, video ads, css, scripts, and other cruft that is the overwhelming fraction of the data downloaded by the page.
Yes, interesting question, but difficult to ask correctly. x86 power consumption is all over the map, varying with features, and the same can be said for ARM. More interesting numbers are MIPS/Watt, FLOPS/Watt, and MACS/Watt. Then of course, MIPS don't translate directly into whether or not the platform "feels snappy". Some of those Watts might be better spent on fast display updates than on MIPS when you look at the total platform experience.
Yes, well, there are times when I've been going for funny and the first mod was insightful (!) so I got karma points for that, right?
But actually, my point was not that people like to be modded 'funny', it's that mods like to read funny posts more than they like to analyze the rhetoric in thoughtful posts -- that's too much work..
No, actually, not that one. That one was intended to be a snarky comment about people posting controversial topics as AC. It was unfortunately taken as a political rant. I don't deny having Libertarian inclinations.
I was referring to comments involving actual data -- for instance once I factually reported how a room full of pointy hair managers viewed open source software, and was accused of being a FUD-monger. No, sorry, I'm a huge and vocal proponent of open software and open hardware -- but because my factual reporting didn't align with people's word view, I was harassed and down-modded as an anti-GPL FUDster. That's simply a state of denial.
This conflicts with my actual experience. Most of the time when I am down-modded it is for one of two reasons: 1) I posted actual, fact-checkable data that is uncomfortable for some mod some where, or 2) I posted first-hand observations that are in conflict with some mod's world view.
It seems that for many mods, once they encounter data that is at conflict with their belief system, their reading comprehension and critical thinking skills evaporate.
On the other hand, if you want cheap Karma points, go for 'funny'. Especially if it is ambiguous as to whether you are going for 'funny' or 'insightful'. The post will zoom to +5. My conclusion: Mods enjoy being entertained, and dislike having their beliefs challenged. I'm shocked! Shocked, I tell you! Seriously: modding is what used to be call 'editing' and editing is hard work.
Correct, the taking clause is in there. Unfortunately, it has been bent to the breaking point. The only need to compensate you if the take the whole thing, but not say, if they take an easement for a railroad right of way but let you keep title to the land. Explain how that is fair. Also, they can take your land and give it to say, a mall developer, claiming that convenient shopping is for the public good.
My problem with eminent domain as it is practiced today is that it doesn't always go for a suitable public purpose, and land owners are not compensated for partial takings.
Mass transit wastes huge amounts of energy, and we can't afford it any more.
That's a bold claim. Where are your numbers?
Originally, from the US Dept. of Transportation. I first saw them in a presentation by one of the lead investigators on the Google self-driving car project. Actually, the figures are well known to everyone in the robotic vehicle community. Go poke around in US DOT data, or the robotic car papers.
Not just the suit situations.... I am partial to landscapes and wildlife -- just the sheer weight of a body, a bag full of lenses, and a tripod is something I am less inclined to carry as I get older. The knock-around point-and-shoot is with me a whole lot more often.
The camera that you will have with you. Whatever that is. In the old days, we used to say "f/8 and be there." -- in other words, 90% of getting the portfolio that you want is having a camera at hand when the action is happening.
You need to ask yourself what exactly is the limitation of your current situation? Resolution? Low light capability? Control over focal length? And you also need to ask yourself how much more hardware you are willing to carry around all the time.
But really, understand exactly what is limiting you in achieving what you want. I once had a lunchtime conversation at work, and a former coworker who had spent his college years working the sales counter in camera shops started going on about Leica lenses and how much better they were than Nikon or Canon. So I said this: Take a look at your last vacation photos. Now look any any random issue of National Geographic. Ask yourself honestly: "Am I being limited by the glass?"
Go learn composition. Learn how to analyze photographs. You'll know soon enough exactly what camera you want.
I notice that you didn't address my point. The government coercion is possible because of the policy of income redistribution. Now, I happen to believe in immunization, and my daughter has the shot records to prove it. Nevertheless, the end does not justify the means. Government coercion is not always bad, I'm glad the government coerces violent criminals into safe keeping. The philosophical argument is about how much government coercion is tolerable.
And my basic point is this: that if this cruft wasn't in the tax code, the government could not coerce you this way. Try to refute that, if you can. It's a statement of mechanics, not philosophy or politics.
I also notice that I was modded down -- hint: There is no "-1 disagree". Clearly that moderation was motivated by ideology, since in my original statement it is pretty difficult to find logical faults.
Sure, there is one place where it works. The London tubes probably do OK as well. But run that analysis for the mass transit system for *any* other metro area in North America. What numbers do you get then? Try it for Northern California. Include the San Francisco to San Jose peninsula, Oakland, Up through Marin, and out to Livermore and Sacramento. (Yes, people commute Bay Area to Sacramento daily). Now look at Cal Train, BART, the San Jose light rail, San Francisco transit buses and trams (you can include or leave out the cable cars as you wish, they are mainly a tourist attraction any more), and all the various municipal bus systems. I bet if you are honest over a 24 hour by 7 day period, you'll be shocked at how much energy is simply wasted on running nearly empty trams and buses around in circles during off-peak times.
Back to my original point. Tell me again why people are pushing for more trains and trams? Jeebus, do the math. Most places it just doesn't work. Nobody is willing to build/operate variable capacity fleets to match the capacity to the load. Without that matching, we're wasting huge amounts of energy. Do. The. Damn. Math. And make it work in general, not just for one or two sweet and unique cases.
The inconvenient truth is that mass transit must be sized for peak loads, and therefore runs no where near capacity most of the time. A train, tram, or bus fully loaded is very energy efficient. A train, tram, or bus lightly loaded uses way more energy per passenger-mile than a car. No transit authority remakes trains between rush hour and mid-day, nor do they have two fleets of buses so that they can switch from long articulateds at rush hour to mini-vans during mid day. Mass transit wastes huge amounts of energy, and we can't afford it any more.
The answer is self-driving cars. We already have door-to-door infrastructure for cars. With self-driving cars road capacity increases because the cars can run closer together and at higher or at least more consistent speeds. A self-driving car is a self-valet-parking vehicle, so parking lots and structures can be moved further from office buildings.
People working on any kind of mass transit solution that involves large vehicles like trains are exactly the fools that are wasting our fossil fuels the fastest. Show me solutions that scale up/down with the daily load fluctuation, and you have my interest.
As a Sili Valley engineer, here is what I want to know: Who are the VC's and board members behind Zynga that told the CEO that this was a good idea? I want to avoid any company that those clowns are involved with. This is not how Silicon Valley works. Stock options are part of the compensation. At two companies I worked at, the stock options turned out to be worthless. That happens a lot. When the options turn out to be worth something, you darn well better let me keep them. If you don't do that, there is no way in hell that I will ever work at any company that any of those VC's or other financiers are involved with, fuck you very much. That is the Silicon Valley social contract. The clowns that did this need to be outed and ostracized.
So I'm thinking... GPS, nice lithium battery, these sound like things I would like to part out so that I could hack the components into some of the robots that I fool with. So, anyway, once somebody puts that stuff on a car, it is a gift to the car owner, right? It's abandon property. So all we need to do is set up a marketplace to clear these things (heck, even eBay) and there are enough electronics hackers looking for cheap GPS units that there should be a ready market for the parts. Once every kid in the neighborhood decides that checking under cars for tracking devices is more lucrative that collecting pop cans, problem solved.
One of my pet peeves is open hardware projects that use closed source or free-beer-crippleware design automation tools. It seems very hard to get people to see how important it is to provide open hardware design files in formats that can be edited with open source DA tools. I even had Lady Ada tell me once in a forum: "Tools don't matter." I found that attitude shocking. I understand that a fully open source tool chain is neither practical nor appropriate for every open hardware project. But I am amazed that open hardware schematics and PCB files are still designed using cripple-ware when at least two good open source tool chains exist.
So several questions: 1) What is your personal take on necessity for open source DA tools where possible? 2) What is the Open Hardware Journal's policy? 3) Is there any hope of seeing a "recursively open artifact" license for open hardware projects? (That is: a license where the design is open, the design file formats are openly documented, and at least one open source tool exists for every step in the tool chain.)
Well, that is the opposite of my experience on Malaysia Airlines. 747 crammed with the maximum number of seats, every seat filled, minimum crew, each "worked" half the flight doing the bare minimum, and got surly if you asked for so much as a glass of water if it forced them to get out of their seats. Totally miserable 13 hour flight.
Slashdot Mirror
Sorry, also look at the Parkinson presentation from the same Stanford Precision Time and Position Conference --
http://scpnt.stanford.edu/pnt/PNT11/2011_presentation_files/01_Parkinson-PNT2011.pdf
He gives a very nice spectrum on slide 4 -- note the little bump at the bottom labeled "Starfire/Omnistar" -- that's the correction signal used by the John Deere precision GPS system, and others, broadcast by Inmarsat III. It's f*ing buried under the proposed LightSquared 10H signal at 1550.2, and still under the skirts of their 10L signal at 1531!
Yup, that has a nice picture illustrating the problem.
ANYTHING carried by Inmarsat III in that band just below GPS L1 is so screwed if LightSquared uses those frequencies!
this is also a pretty clear indication that FCC was bought off at a high level, and their technical types didn't get to look at it -- they would have screamed.
Yes, that seems to be happening a lot lately. Good, bottom-up technical analysis from FCC engineers get overridden by political concerns. Broadband over Power Lines (BPL) is another egregious example of politics forcing idiotic technical decisions. Spectrum sharing compatibility analysis seems to have been left back in the last millennium some how.
OK, I quickly looked over the excellent presentation that you link to. I don't see where it shows a GPS precision-enhancing signal in L-band getting swamped. It *does* show 15 kW (!) terrestrial base stations very near the GPS L1 band having the potential to get past the roofing filter in a GPS, as my previous post was attempting to yak about.
I was under the impression that differential GPS used short-range terrestrial VHF for a localization signal from another GPS receiver looking at the normal GPS signal -- is my understanding stale? Has something new come along when I wasn't looking?
But holey schmoley, 15KW at 1.5 GHZ? That's manly. That takes a moderate amount of effort. It also raises some RF safety issues -- what kind of antennas are they using with this? What is the EIRP?
Anyway, for whatever reason, my previous post has been generously modded "+5 insightful" at the moment, when it's really just speculation based on "here's how radios work in general"... I'm not a GPS expert. "+/-? Plausible BS" is probably a more accurate mod score.
It's very unlikely to be lightspeed signal bleeding over out of their channel. That is reasonably easy to control, and it would show up in 100% of tested receivers. More likely, this is "adjacent channel interference". It is much harder to get a receiver to reject signals in adjacent channels. It takes a difficult/expensive to construct filter. If you go back to the old days of television, you'll note that you don't find adjacent channels allocated in major markets, for instance, because in the early days it was essentially impossible to build a receiver that could reject a strong signal on an adjacent channel. So here we have a case of a receiver looking for a very weak signal, and on an adjacent channel there is a strong local transmitter that you are trying to reject. I'm no surprised that there are issues. Also, because GPS has up till now not had strong nearby, adjacent signals to reject, it could actually be that the first mixer is getting overloaded, so the damage is done before you even get to the first IF filter.
Actually.... Forth-sightful is just the address. So:
Forth-sightful @ 1 + !
is more correct. Or:
Forth-sightful @1+
which might not be quite right either.... this is why Forth has a blessedly small cult following.
Continuing in the tradition of Forth programmers everywhere to define new words and compress the code until the entire application fits on one line, and is indistinguishable from modem noise:
Forth-sightful 1+
the word '1+' (or a variant) is often defined because incrementing the top of stack is so useful.
And if you want to see the result:
Forth-sightful 1+ .
Forth has its place, but I'd hate to implement anything big using it.
In principal, I'm OK with some form of metered usage. But I don't want to pay for the bandwidth associated with advertising -- if all I want out of a page is the 2K of text that dispenses useful information, I don't want to pay for downloading all the Flash ads, video ads, css, scripts, and other cruft that is the overwhelming fraction of the data downloaded by the page.
Yes, interesting question, but difficult to ask correctly. x86 power consumption is all over the map, varying with features, and the same can be said for ARM. More interesting numbers are MIPS/Watt, FLOPS/Watt, and MACS/Watt. Then of course, MIPS don't translate directly into whether or not the platform "feels snappy". Some of those Watts might be better spent on fast display updates than on MIPS when you look at the total platform experience.
Just put the California Department of Fish and Game in charge of maintaining a self-sustaining breeding population of mosquitoes.
Yes, well, there are times when I've been going for funny and the first mod was insightful (!) so I got karma points for that, right?
But actually, my point was not that people like to be modded 'funny', it's that mods like to read funny posts more than they like to analyze the rhetoric in thoughtful posts -- that's too much work..
No, actually, not that one. That one was intended to be a snarky comment about people posting controversial topics as AC. It was unfortunately taken as a political rant. I don't deny having Libertarian inclinations.
I was referring to comments involving actual data -- for instance once I factually reported how a room full of pointy hair managers viewed open source software, and was accused of being a FUD-monger. No, sorry, I'm a huge and vocal proponent of open software and open hardware -- but because my factual reporting didn't align with people's word view, I was harassed and down-modded as an anti-GPL FUDster. That's simply a state of denial.
This conflicts with my actual experience. Most of the time when I am down-modded it is for one of two reasons: 1) I posted actual, fact-checkable data that is uncomfortable for some mod some where, or 2) I posted first-hand observations that are in conflict with some mod's world view.
It seems that for many mods, once they encounter data that is at conflict with their belief system, their reading comprehension and critical thinking skills evaporate.
On the other hand, if you want cheap Karma points, go for 'funny'. Especially if it is ambiguous as to whether you are going for 'funny' or 'insightful'. The post will zoom to +5. My conclusion: Mods enjoy being entertained, and dislike having their beliefs challenged. I'm shocked! Shocked, I tell you! Seriously: modding is what used to be call 'editing' and editing is hard work.
Correct, the taking clause is in there. Unfortunately, it has been bent to the breaking point. The only need to compensate you if the take the whole thing, but not say, if they take an easement for a railroad right of way but let you keep title to the land. Explain how that is fair. Also, they can take your land and give it to say, a mall developer, claiming that convenient shopping is for the public good.
My problem with eminent domain as it is practiced today is that it doesn't always go for a suitable public purpose, and land owners are not compensated for partial takings.
Mass transit wastes huge amounts of energy, and we can't afford it any more.
That's a bold claim. Where are your numbers?
Originally, from the US Dept. of Transportation. I first saw them in a presentation by one of the lead investigators on the Google self-driving car project. Actually, the figures are well known to everyone in the robotic vehicle community. Go poke around in US DOT data, or the robotic car papers.
Oddly, people don't like to live that way.
Not just the suit situations.... I am partial to landscapes and wildlife -- just the sheer weight of a body, a bag full of lenses, and a tripod is something I am less inclined to carry as I get older. The knock-around point-and-shoot is with me a whole lot more often.
This.
The camera that you will have with you. Whatever that is. In the old days, we used to say "f/8 and be there." -- in other words, 90% of getting the portfolio that you want is having a camera at hand when the action is happening.
You need to ask yourself what exactly is the limitation of your current situation? Resolution? Low light capability? Control over focal length? And you also need to ask yourself how much more hardware you are willing to carry around all the time.
But really, understand exactly what is limiting you in achieving what you want. I once had a lunchtime conversation at work, and a former coworker who had spent his college years working the sales counter in camera shops started going on about Leica lenses and how much better they were than Nikon or Canon. So I said this: Take a look at your last vacation photos. Now look any any random issue of National Geographic. Ask yourself honestly: "Am I being limited by the glass?"
Go learn composition. Learn how to analyze photographs. You'll know soon enough exactly what camera you want.
But have it with you.
What government? Any government.
I notice that you didn't address my point. The government coercion is possible because of the policy of income redistribution. Now, I happen to believe in immunization, and my daughter has the shot records to prove it. Nevertheless, the end does not justify the means. Government coercion is not always bad, I'm glad the government coerces violent criminals into safe keeping. The philosophical argument is about how much government coercion is tolerable.
And my basic point is this: that if this cruft wasn't in the tax code, the government could not coerce you this way. Try to refute that, if you can. It's a statement of mechanics, not philosophy or politics.
I also notice that I was modded down -- hint: There is no "-1 disagree". Clearly that moderation was motivated by ideology, since in my original statement it is pretty difficult to find logical faults.
This is Slashdot, you collectivists are safe here. No need to hide your leftist opinion behind Anonymous Coward posting.
Get all this crazy cruft out of the tax code and then the government can't use it as a lever/hammer against you.
Sure, there is one place where it works. The London tubes probably do OK as well. But run that analysis for the mass transit system for *any* other metro area in North America. What numbers do you get then? Try it for Northern California. Include the San Francisco to San Jose peninsula, Oakland, Up through Marin, and out to Livermore and Sacramento. (Yes, people commute Bay Area to Sacramento daily). Now look at Cal Train, BART, the San Jose light rail, San Francisco transit buses and trams (you can include or leave out the cable cars as you wish, they are mainly a tourist attraction any more), and all the various municipal bus systems. I bet if you are honest over a 24 hour by 7 day period, you'll be shocked at how much energy is simply wasted on running nearly empty trams and buses around in circles during off-peak times.
Back to my original point. Tell me again why people are pushing for more trains and trams? Jeebus, do the math. Most places it just doesn't work. Nobody is willing to build/operate variable capacity fleets to match the capacity to the load. Without that matching, we're wasting huge amounts of energy. Do. The. Damn. Math. And make it work in general, not just for one or two sweet and unique cases.
The inconvenient truth is that mass transit must be sized for peak loads, and therefore runs no where near capacity most of the time. A train, tram, or bus fully loaded is very energy efficient. A train, tram, or bus lightly loaded uses way more energy per passenger-mile than a car. No transit authority remakes trains between rush hour and mid-day, nor do they have two fleets of buses so that they can switch from long articulateds at rush hour to mini-vans during mid day. Mass transit wastes huge amounts of energy, and we can't afford it any more.
The answer is self-driving cars. We already have door-to-door infrastructure for cars. With self-driving cars road capacity increases because the cars can run closer together and at higher or at least more consistent speeds. A self-driving car is a self-valet-parking vehicle, so parking lots and structures can be moved further from office buildings.
People working on any kind of mass transit solution that involves large vehicles like trains are exactly the fools that are wasting our fossil fuels the fastest. Show me solutions that scale up/down with the daily load fluctuation, and you have my interest.
As a Sili Valley engineer, here is what I want to know: Who are the VC's and board members behind Zynga that told the CEO that this was a good idea? I want to avoid any company that those clowns are involved with. This is not how Silicon Valley works. Stock options are part of the compensation. At two companies I worked at, the stock options turned out to be worthless. That happens a lot. When the options turn out to be worth something, you darn well better let me keep them. If you don't do that, there is no way in hell that I will ever work at any company that any of those VC's or other financiers are involved with, fuck you very much. That is the Silicon Valley social contract. The clowns that did this need to be outed and ostracized.
So I'm thinking... GPS, nice lithium battery, these sound like things I would like to part out so that I could hack the components into some of the robots that I fool with. So, anyway, once somebody puts that stuff on a car, it is a gift to the car owner, right? It's abandon property. So all we need to do is set up a marketplace to clear these things (heck, even eBay) and there are enough electronics hackers looking for cheap GPS units that there should be a ready market for the parts. Once every kid in the neighborhood decides that checking under cars for tracking devices is more lucrative that collecting pop cans, problem solved.
Bruce,
One of my pet peeves is open hardware projects that use closed source or free-beer-crippleware design automation tools. It seems very hard to get people to see how important it is to provide open hardware design files in formats that can be edited with open source DA tools. I even had Lady Ada tell me once in a forum: "Tools don't matter." I found that attitude shocking. I understand that a fully open source tool chain is neither practical nor appropriate for every open hardware project. But I am amazed that open hardware schematics and PCB files are still designed using cripple-ware when at least two good open source tool chains exist.
So several questions:
1) What is your personal take on necessity for open source DA tools where possible?
2) What is the Open Hardware Journal's policy?
3) Is there any hope of seeing a "recursively open artifact" license for open hardware projects? (That is: a license where the design is open, the design file formats are openly documented, and at least one open source tool exists for every step in the tool chain.)
Well, that is the opposite of my experience on Malaysia Airlines. 747 crammed with the maximum number of seats, every seat filled, minimum crew, each "worked" half the flight doing the bare minimum, and got surly if you asked for so much as a glass of water if it forced them to get out of their seats. Totally miserable 13 hour flight.