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I've never heard that or seen any evidence of it. We've met Canadians just recently that cruise to Cuba quite frequently and they reported no such issues. It would be technically difficult to jam GPS signals over any distance other than by satellite or high altitude airplane. I understood that "selective availability mk2" (or whatever it's known as) is the capability to selectively deny access to GPS signals over limited geographical areas, maybe this has some bearing ? Boo |
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On Sat, 17 Jul 2010 11:22:42 +0100, Boo
wrote: I understood that "selective availability mk2" (or whatever it's known as) is the capability to selectively deny access to GPS signals over limited geographical areas, maybe this has some bearing ? It would be limited mostly to "line of sight" distances, and Cuba is not known for being a technical power house with unlimited financial resources. |
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Wayne.B wrote:
On Sat, 17 Jul 2010 11:22:42 +0100, Boo wrote: I understood that "selective availability mk2" (or whatever it's known as) is the capability to selectively deny access to GPS signals over limited geographical areas, maybe this has some bearing ? It would be limited mostly to "line of sight" distances, and Cuba is not known for being a technical power house with unlimited financial resources. You and the previous poster are giving the appearance of not knowing what selective availability (SA) is. SA is a feature of GPS that permits the civilian positioning feature of GPS to be subject to a psuedo random position error. This error affects all GPS units within a particular area and is only "line of sight" in that it affects all units within line of sight of particular satellites, so the area can be huge or indeed global as it was until 2000 when the feature was turned off. Your comment makes it appear that you are confused between jamming and SA. At present GPS is denied in particular areas using other means which are less susceptible to correction. SA could be defeated by the use of dGPS and the US have stated it will never be turned back on again. You seem to have been attempting to claim that GPS cannot be jammed or denied, in this you are wrong. The methods used are not however public knowledge although from time to time NOTAMS and similar publications will indicate in which areas GPS is being denied for trials. |
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On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth)
wrote: You seem to have been attempting to claim that GPS cannot be jammed Incorrect. I am claiming that it is unlikely that GPS is being jammed by the Cuban government. |
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Wayne.B wrote:
On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth) wrote: You seem to have been attempting to claim that GPS cannot be jammed Incorrect. I am claiming that it is unlikely that GPS is being jammed by the Cuban government. Well no, and you had to trim a lot from my post to cover up the mistakes you made. FWIW, jamming is low tech and the Cuban government is probably able to do it as well as the British government. OTOH if GPS is being jammed near Cuba, I'd point the finger towards another government with a rabid hatred of Cuba. |
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On Sat, 17 Jul 2010 20:52:41 +0100, (Steve Firth)
wrote: Incorrect. I am claiming that it is unlikely that GPS is being jammed by the Cuban government. Well no, and you had to trim a lot from my post to cover up the mistakes you made. FWIW, jamming is low tech and the Cuban government is probably able to do it as well as the British government. OTOH if GPS is being jammed near Cuba, I'd point the finger towards another government with a rabid hatred of Cuba. Have you ever looked at the age and detail level of the commonly available Cuban charts? If so, you'd know that the problem is not with GPS. I was cruising within 40 miles of the Cuban coast just a month ago and our GPS was spot on with up to date electronic CMAP charts of the area. Cruise ships and commercial shipping transit within sight of the Cuban coast all of the time and they are having no issues. What *is* happening, is that some, but by no means all, cruisers are getting into trouble because of bad charts and/or inattention. When that happens it is much less embarassing to blame the whole incident on mysterious forces and conspiracy theories. PS, no one in the US really hates Cuba except for a small number of reactionaries who escaped after the Castro takeover. |
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I understood that "selective availability mk2" (or whatever it's known as) is
the capability to selectively deny access to GPS signals over limited geographical areas, maybe this has some bearing ? It would be limited mostly to "line of sight" distances, and Cuba is not known for being a technical power house with unlimited financial resources. True, but America is ? Boo |
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Wayne.B wrote:
Have you ever looked at the age and detail level of the commonly available Cuban charts? No, I looked at the bilge you were talking about GPS and pointed out that it was bilge. And for some reason (lack of balls, inability to admit fault?) you keep running away from your failure. No one mentioned "conspiracy" or "mysterious forces" before you started wibbling about them. PS, no one in the US really hates Cuba except for a small number of reactionaries who escaped after the Castro takeover. Right, so your government hasn't had sanctions in place against Cuba since the 1950s? Oh look, porcine aviation. Perhaps you could learn to read BTW. I pointed out that your government has a rabid hatred of Cuba. You then tried to turn that into a generalisation about Americans with your "no one in the US" bull. |
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"Steve Firth" wrote in message .. . Wayne.B wrote: On Sat, 17 Jul 2010 11:22:42 +0100, Boo wrote: I understood that "selective availability mk2" (or whatever it's known as) is the capability to selectively deny access to GPS signals over limited geographical areas, maybe this has some bearing ? It would be limited mostly to "line of sight" distances, and Cuba is not known for being a technical power house with unlimited financial resources. You and the previous poster are giving the appearance of not knowing what selective availability (SA) is. SA is a feature of GPS that permits the civilian positioning feature of GPS to be subject to a psuedo random position error. This error affects all GPS units within a particular area and is only "line of sight" in that it affects all units within line of sight of particular satellites, so the area can be huge or indeed global as it was until 2000 when the feature was turned off. Your comment makes it appear that you are confused between jamming and SA. At present GPS is denied in particular areas using other means which are less susceptible to correction. SA could be defeated by the use of dGPS and the US have stated it will never be turned back on again. You seem to have been attempting to claim that GPS cannot be jammed or denied, in this you are wrong. The methods used are not however public knowledge although from time to time NOTAMS and similar publications will indicate in which areas GPS is being denied for trials. Exactly right Steve, Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR |
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Steve Firth wrote:
Wayne.B wrote: Have you ever looked at the age and detail level of the commonly available Cuban charts? No, So you know nothing about Cuban charts. And you know nothing about GPS navigation in Cuban waters. Does that sum it up? Jim |
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WaIIy wrote:
[snip] Where did you go to logic school ? Two universities, and you? I note that you have avoided the issue again. You really are a eunuch, aren't you? You whine about a generalization and make one in the same paragraph. Untrue. |
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On Sun, 18 Jul 2010 11:32:55 +0100, (Steve Firth)
wrote (with clarity & insight): WaIIy wrote: [snip] Where did you go to logic school ? Two universities, and you? I note that you have avoided the issue again. You really are a eunuch, aren't you? You whine about a generalization and make one in the same paragraph. Untrue. Those universities should've illustrated to you that being an asshole isn't a good position to take when trying to make a point. But it's a great way to make it on a kill list. Congratulations. |
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On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote
(with clarity & insight): Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR I've been using plain ol' GPS devices in & around DC for years with no issues. What am I missing? |
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Wayne R. wrote:
Those universities should've illustrated to you that being an asshole isn't a good position to take when trying to make a point. So once more, nothing to contriute from you but blather. But it's a great way to make it on a kill list. Congratulations. Those who feel the need to ostentatiously announce the contents of their kill file (while not apparently knowing what a kill file is) are worthless prats, so why I should I care what you do? |
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Wayne R. wrote:
On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote (with clarity & insight): Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR I've been using plain ol' GPS devices in & around DC for years with no issues. What am I missing? a) A brain. b) A clue. Not necessarily in that order. |
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"Wayne R." wrote in message ... On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote (with clarity & insight): Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR I've been using plain ol' GPS devices in & around DC for years with no issues. What am I missing? I have a Ram Mount in my GMC Yukon we use as a travel car, On this mount I place a laptop and more recently a Netbook computer on the Ram and use MS Streets & Trips with a USB "puck" as the GPS receiver/antenna. On the many trips south from Pa to Fla as I use the DC Beltway and with the GPS in tracking mode it becomes "lost". The 1st time this happened I thought it was the unit itself and told it to recalculate the route from my current location. It couldnt determine my current location until we were merging back onto I-95. It simply didn't know where it was. Weather was not a factor (clear skies) nor was it a lack of GPS signal (it still showed as tracking 8 sats). This "problem" is repeatable 100% of the time on various trips thru the area. Similarly, During a trip for my daughters wedding and subsequent trips to Ft Hood, when approching base housing the same thing happens. Every time. When I asked my son-in-law about it he would only say "Yeah, kinda neat huh?" In conversations with my youngest daughters soon-to-be-husband who was home on leave from Jihadistan, he indicated that even there a few sites are so protected. Now, in northern NJ and northern Wi there are coverage gaps where the GPS can't resolve it's location, but these are a different situation as the unit tells me it can't find itself and why. Not so with the DC & Ft. Hood issues. Regards, JR |
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JR wrote:
Now, in northern NJ and northern Wi there are coverage gaps where the GPS can't resolve it's location, but these are a different situation as the unit tells me it can't find itself and why. Not so with the DC & Ft. Hood issues. Wayne is refusing to admit that jamming occurs, however here's a typical British NOTAM from 06-June-2007: "GPS SIGNAL JAMMING TRIALS. JAMMER LOCATED WITHIN 0.5 [nautical miles] OF 5016N 00516W (PORTREATH, CORNWALL). ACTIVITY MAY AFFECT AIRCRAFT WITHIN 6NM RADIUS FLYING BELOW FL300 [30,000 feet] ... DURING TRIAL PERIODS, GPS RECEIVERS MAY SUFFER INTERMITTENT/TOTAL FAILURE, OR GIVE INCORRECT POSITION INFO ..." Note the last part, it's not just jamming as in drowing out the signal with noise, it's more subtle than that the jamming may involve feeding the GPS incorrect position info. This, in the World According to Wayne, cannot happen and any claim that it does happen is some sort of appeal to irrationality. |
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On Sun, 18 Jul 2010 15:13:57 +0100, (Steve Firth)
wrote: any claim that it does happen is some sort of appeal to irrationality. Steve, with all due respect I think you've got all the claims to irrationality pretty well covered. Cheers. |
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Wayne.B wrote:
On Sun, 18 Jul 2010 15:13:57 +0100, (Steve Firth) wrote: any claim that it does happen is some sort of appeal to irrationality. Steve, with all due respect I think you've got all the claims to irrationality pretty well covered. yawn Anything to contribute other than vacuous abuse "Wayne"? No, that's obvious. |
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On Sun, 18 Jul 2010 09:56:35 -0400, "JR" wrote
(with clarity & insight): "Wayne R." wrote in message .. . On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote (with clarity & insight): Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR I've been using plain ol' GPS devices in & around DC for years with no issues. What am I missing? I have a Ram Mount in my GMC Yukon we use as a travel car, On this mount I place a laptop and more recentlya Netbook computer on the Ram and use MS Streets & Trips with a USB "puck" as the GPS receiver/antenna. On the many trips south from Pa to Fla as I use the DC Beltway and with the GPS in tracking mode it becomes "lost". The 1st time this happened I thought it was the unit itself and told it to recalculate the route from my current location. It couldnt determine my current location until we were merging back onto I-95. It simply didn't know where it was. Weather was not a factor (clear skies) nor was it a lack of GPS signal (it still showed as tracking 8 sats). This "problem" is repeatable 100% of the time on various trips thru the area. Similarly, During a trip for my daughters wedding and subsequent trips to Ft Hood, when approching base housing the same thing happens. Every time. When I asked my son-in-law about it he would only say "Yeah, kinda neat huh?" In conversations with my youngest daughters soon-to-be-husband who was home on leave from Jihadistan, he indicated that even there a few sites are so protected. Now, in northern NJ and northern Wi there are coverage gaps where the GPS can't resolve it's location, but these are a different situation as the unit tells me it can't find itself and why. Not so with the DC & Ft. Hood issues. Regards, JR I've found places where I've seen repeatable problems with one type of receiver but not another. (Sometimes problems come & go, and in those circumstances I've attributed it to constellation/reflection variations.) I've spent a lot of time near the White House, Pentagon, Ft. Meade, Langley, etc., in DC without any loss of lock - some of the places that seem most likely to have constant jamming? When your receiver "tells me it can't find itself and why", what does it say? |
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In article ,
Wayne.B wrote: On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth) wrote: You seem to have been attempting to claim that GPS cannot be jammed Incorrect. I am claiming that it is unlikely that GPS is being jammed by the Cuban government. Not to dis Wayne, but MANY Governments that are NOT Allies with the USA, have purchased GPS Jamming Technology, from the Russians, for the simple Paranoid Reason, that they can turn it ON, and it will keep some of our Lower Tech GPS Guided Munitions from hitting their intended Targets, should we feel the need to go to War with them.... Most of the more Modern Guided Munitions now use other Primary Guidance Systems, and GPS is only a Backup Slave System, that can be set to be compared with the Primary System. These same Governments, test these Systems regularly... Our own Government DOES protect MANY of our most important Federal AREAS, using similar Technologies, for the same reasons. GPS is great, but it is NOT the One Size Fits ALL Munition Aiming System.... -- Bruce in alaska add path after fast to reply |
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Bruce in alaska wrote:
Most of the more Modern Guided Munitions now use other Primary Guidance Systems Great Random CaPitalisation tHere. FWIW, a great many Old Guided Munitions use other Primary gUiDancE sySteMs. |
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On Sun, 18 Jul 2010 12:19:23 -0800, Bruce in alaska
wrote: Not to dis Wayne, but MANY Governments that are NOT Allies with the USA, have purchased GPS Jamming Technology, from the Russians, It was never my point that GPS could not be jammed. My point was, and is, that such jamming would by necessity be relatively short range because of the microwave frequencies involved. The only exception would be some sort of systemic jamming that originated within the satellites themselves. It's my understanding that jamming of that sort would affect all users. |
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Wayne.B wrote:
On Sun, 18 Jul 2010 12:19:23 -0800, Bruce in alaska wrote: Not to dis Wayne, but MANY Governments that are NOT Allies with the USA, have purchased GPS Jamming Technology, from the Russians, It was never my point that GPS could not be jammed. My point was, and is, that such jamming would by necessity be relatively short range because of the microwave frequencies involved. The only exception would be some sort of systemic jamming that originated within the satellites themselves. It's my understanding that jamming of that sort would affect all users. You've already been given details of two types of jamming and SA which is not jamming. However at present you seem to be keener on jamming your head up your arse and avoiding admitting the fact. |
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"Wayne R." wrote in message ... On Sun, 18 Jul 2010 09:56:35 -0400, "JR" wrote (with clarity & insight): "Wayne R." wrote in message . .. On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote (with clarity & insight): Washington DC and Fort Hood in upstate NY are just two places I have personal knowlege of where GPS is munged for security purposes. Regards, JR I've been using plain ol' GPS devices in & around DC for years with no issues. What am I missing? I have a Ram Mount in my GMC Yukon we use as a travel car, On this mount I place a laptop and more recentlya Netbook computer on the Ram and use MS Streets & Trips with a USB "puck" as the GPS receiver/antenna. On the many trips south from Pa to Fla as I use the DC Beltway and with the GPS in tracking mode it becomes "lost". The 1st time this happened I thought it was the unit itself and told it to recalculate the route from my current location. It couldnt determine my current location until we were merging back onto I-95. It simply didn't know where it was. Weather was not a factor (clear skies) nor was it a lack of GPS signal (it still showed as tracking 8 sats). This "problem" is repeatable 100% of the time on various trips thru the area. Similarly, During a trip for my daughters wedding and subsequent trips to Ft Hood, when approching base housing the same thing happens. Every time. When I asked my son-in-law about it he would only say "Yeah, kinda neat huh?" In conversations with my youngest daughters soon-to-be-husband who was home on leave from Jihadistan, he indicated that even there a few sites are so protected. Now, in northern NJ and northern Wi there are coverage gaps where the GPS can't resolve it's location, but these are a different situation as the unit tells me it can't find itself and why. Not so with the DC & Ft. Hood issues. Regards, JR I've found places where I've seen repeatable problems with one type of receiver but not another. (Sometimes problems come & go, and in those circumstances I've attributed it to constellation/reflection variations.) I've spent a lot of time near the White House, Pentagon, Ft. Meade, Langley, etc., in DC without any loss of lock - some of the places that seem most likely to have constant jamming? When your receiver "tells me it can't find itself and why", what does it say? Wayne, the receiver will tell me GPS signal not available (usually weather related), or will indicate not enough Sats to resolve position. And it will display how many sats it "sees". With the DC and Ft Hood issues it says nothing. It just doesn't work. Regards, JR |
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On Sun, 18 Jul 2010 20:19:22 -0500, Richard Casady
wrote: Just where are these areas without coverage? Hint: the G in GPS stands for Global. It's like taxes: everywhere. Apparently there is this conspiracy theory that "someone" is jamming GPS signals near the coast of Cuba. There is plenty of evidence that GPS normally works just fine in that area but when people run aground it is convenient for the ego to have some alternative explanation. |
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Richard Casady wrote:
On Mon, 19 Jul 2010 01:42:33 GMT, (patric albutat) wrote: So how exactly are we going to create superior charts in regions with no GPS coverage? Or what use would these charts be to a sailor trying to navigate a tricky coast without sat nav to give him his position? Just where are these areas without coverage? http://waas.stanford.edu/~wwu/papers...itch_stu95.pdf http://waas.stanford.edu/~wwu/papers...F/SeoIES08.pdf http://www.agu.org/pubs/crossref/200...RS003066.shtml http://www.fly-low.com/features02/gpsdenial.html https://www.fbo.gov/index?s=opportun...f11c050aeb be 7682bc9ba408a&tab=core&_cview=1 http://www.aviationkb.com/Uwe/Forum....Interference-T esting-711-reporting Note that the published radius of jamming by the USG is 180 - 400 nm (reported for both Maryland and China Lake) something that Wayne refuses to acknowledge as he repeats that jamming isn't possible over a large area. Presumably the NOTAMS stating that jamming was occuring over a wide area of sea off Cornwall previously posted doesn't mean anything to Wayne because it's happening somewhere foreign. Hint: the G in GPS stands for Global. It's like taxes: everywhere. Then there's the World Series ... so that according to you involves everyone in the world? It doesn't even involve a significant fraction of the world's nations. Does Universal Studios involve the entire Universe? |
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(Steve Firth) wrote in news:1jlv6sr.1b9ejr91nd0q9uN%%
: Richard Casady wrote: On Mon, 19 Jul 2010 01:42:33 GMT, (patric albutat) wrote: So how exactly are we going to create superior charts in regions with no GPS coverage? Or what use would these charts be to a sailor trying to navigate a tricky coast without sat nav to give him his position? I guess it had to come......No GPS, no way to fix your position... |
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In article ,
Richard Casady wrote: On Mon, 19 Jul 2010 01:42:33 GMT, (patric albutat) wrote: So how exactly are we going to create superior charts in regions with no GPS coverage? Or what use would these charts be to a sailor trying to navigate a tricky coast without sat nav to give him his position? Just where are these areas without coverage? Hint: the G in GPS stands for Global. It's like taxes: everywhere. Casady Just about ANY Military Nuclear Site in the USA. Most of the FEMA Bunkers. Most of the SAC Bases have that capability, but only test it unless at DefCon 2 or higher. White House & Capitol Building, depending on the immediate Threat Level. Places like that here in this country. Overseas, Many of the National Parliament buildings, and Presidential Palaces, and major Military installations, and places like that. Global means Global Coverage from the Sky, not global coverage on the Ground when local Jammers are active. This isn't Rocket Science, and many Militaries around the world can, and do Jam the Civilian Datastreams, within their boarders. The P-Code & Military Datastreams, are a lot more resistant to such Jamming. -- Bruce in alaska add path after fast to reply |
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On Mon, 19 Jul 2010 11:48:28 -0800, Bruce in alaska
wrote: Just about ANY Military Nuclear Site in the USA. Most of the FEMA Bunkers. Most of the SAC Bases have that capability, but only test it unless at DefCon 2 or higher. White House & Capitol Building, depending on the immediate Threat Level. Places like that here in this country. Overseas, Many of the National Parliament buildings, and Presidential Palaces, and major Military installations, and places like that. Global means Global Coverage from the Sky, not global coverage on the Ground when local Jammers are active. This isn't Rocket Science, and many Militaries around the world can, and do Jam the Civilian Datastreams, within their boarders. The P-Code & Military Datastreams, are a lot more resistant to such Jamming. Good information. Do you have an estimate of how far offshore a local jamming effort might extend? |
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NOTAM:
Oakland Center (Fremont CA) [ZOA]: April NOTAM #31 issued by Gps Notam OA [GPS] Navigation GPS is unreliable and May BE unavailable WITHIN A 375 nautical miles RADIUS of 393101N/1175659W LOVELOCK / LLC / VORTAC 141.25 DEGREE radial at 46.65 nautical miles, at FL400; decreasing in area with DECREASE in altitude to 290 nautical miles RADIUS at FL250; 220 nautical miles RADIUS at 10000 ft. mean sea level, and 220 nautical miles RADIUS at 4000 ft. above ground level. effective from April 09th, 2010 at 06:00 AM PST (1004091400) - April 09th, 2010 at 11:30 AM PST (1004091930) |
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On Mon, 19 Jul 2010 23:18:19 -0500, cavelamb
wrote: NOTAM: Oakland Center (Fremont CA) [ZOA]: April NOTAM #31 issued by Gps Notam OA [GPS] Navigation GPS is unreliable and May BE unavailable WITHIN A 375 nautical miles RADIUS of 393101N/1175659W LOVELOCK / LLC / VORTAC 141.25 DEGREE radial at 46.65 nautical miles, at FL400; decreasing in area with DECREASE in altitude to 290 nautical miles RADIUS at FL250; 220 nautical miles RADIUS at 10000 ft. mean sea level, and 220 nautical miles RADIUS at 4000 ft. above ground level. effective from April 09th, 2010 at 06:00 AM PST (1004091400) - April 09th, 2010 at 11:30 AM PST (1004091930) Those ranges quoted are for aircraft thousands of feet above sea level. The jamming range would be much shorter for boats, probably 10 miles or less. |
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Wayne.B wrote:
On Mon, 19 Jul 2010 23:18:19 -0500, cavelamb wrote: NOTAM: Oakland Center (Fremont CA) [ZOA]: April NOTAM #31 issued by Gps Notam OA [GPS] Navigation GPS is unreliable and May BE unavailable WITHIN A 375 nautical miles RADIUS of 393101N/1175659W LOVELOCK / LLC / VORTAC 141.25 DEGREE radial at 46.65 nautical miles, at FL400; decreasing in area with DECREASE in altitude to 290 nautical miles RADIUS at FL250; 220 nautical miles RADIUS at 10000 ft. mean sea level, and 220 nautical miles RADIUS at 4000 ft. above ground level. effective from April 09th, 2010 at 06:00 AM PST (1004091400) - April 09th, 2010 at 11:30 AM PST (1004091930) Those ranges quoted are for aircraft thousands of feet above sea level. The jamming range would be much shorter for boats, probably 10 miles or less. aSSuming it's a linear relationship, I get 202 mile radius... -- Richard Lamb |
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On 7/20/2010 1:41 AM, cavelamb wrote:
Wayne.B wrote: On Mon, 19 Jul 2010 23:18:19 -0500, cavelamb wrote: NOTAM: Oakland Center (Fremont CA) [ZOA]: April NOTAM #31 issued by Gps Notam OA [GPS] Navigation GPS is unreliable and May BE unavailable WITHIN A 375 nautical miles RADIUS of 393101N/1175659W LOVELOCK / LLC / VORTAC 141.25 DEGREE radial at 46.65 nautical miles, at FL400; decreasing in area with DECREASE in altitude to 290 nautical miles RADIUS at FL250; 220 nautical miles RADIUS at 10000 ft. mean sea level, and 220 nautical miles RADIUS at 4000 ft. above ground level. effective from April 09th, 2010 at 06:00 AM PST (1004091400) - April 09th, 2010 at 11:30 AM PST (1004091930) Those ranges quoted are for aircraft thousands of feet above sea level. The jamming range would be much shorter for boats, probably 10 miles or less. aSSuming it's a linear relationship, I get 202 mile radius... Not linear: for a ground level jammer, The line of sight estimator for distance versus height above sea level goes something like this: distance n.m. = 1.2 sqrt (Height ft MSL) |
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Those ranges quoted are for aircraft thousands of feet above sea level. The jamming range would be much shorter for boats, probably 10 miles or less. aSSuming it's a linear relationship, I get 202 mile radius... Not linear: for a ground level jammer, The line of sight estimator for distance versus height above sea level goes something like this: distance n.m. = 1.2 sqrt (Height ft MSL) ...and of course that assumes that the emitter is at sea level, so if it is at any appreciable height (or in another aircraft) then you have to add the result of the same equation again!! Jeff |
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brian whatcott wrote:
Not linear: for a ground level jammer, The line of sight estimator for distance versus height above sea level goes something like this: distance n.m. = 1.2 sqrt (Height ft MSL) That calculation follows directly from the Taylor series for Cosine: 1 - x^2/2! + x^4/4! - ... It means that for very small angles, the height above the sea is 1 - (1 - x^2/2!) = x^2/2! = x^2/2 (when R == 1) Insert the radius of the Earth (in nautical miles, 3500 or so) and multiply the result by the number of feet in a nautical mile (about 6000+) and the 1.2 factor should pop out. Terje -- - Terje.Mathisen at tmsw.no "almost all programming can be viewed as an exercise in caching" |
May a "landlubber" comment? - was[ Help create better charts]
On 25/07/10 10:54, Jeff wrote:
Those ranges quoted are for aircraft thousands of feet above sea level. The jamming range would be much shorter for boats, probably 10 miles or less. aSSuming it's a linear relationship, I get 202 mile radius... Not linear: for a ground level jammer, The line of sight estimator for distance versus height above sea level goes something like this: distance n.m. = 1.2 sqrt (Height ft MSL) ..and of course that assumes that the emitter is at sea level, so if it is at any appreciable height (or in another aircraft) then you have to add the result of the same equation again!! and ignores the surface effect that allows UK TV & VHF signals to be picked up as far away as in the Netherlands. |
May a "landlubber" comment? - was[ Help create better charts]
The line of sight estimator for distance versus height above sea level goes something like this: distance n.m. = 1.2 sqrt (Height ft MSL) That calculation follows directly from the Taylor series for Cosine: 1 - x^2/2! + x^4/4! - ... It means that for very small angles, the height above the sea is 1 - (1 - x^2/2!) = x^2/2! = x^2/2 (when R == 1) Insert the radius of the Earth (in nautical miles, 3500 or so) and multiply the result by the number of feet in a nautical mile (about 6000+) and the 1.2 factor should pop out. Terje For a more exact result you only need to use Pythagoras. Jeff |
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