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Offshore is relative. I’ve been able to receive a fix to within about 20 miles of accuracy near Bermuda. That’s better than nothing and about what you can expect with a sextant. This was done with a good LORAN, a Micrologic 9000S. Some of the less expensive units have a less sensitive receiver and won’t provide a fix that far out. Even though offshore coverage is sketchy, its worth having a backup for coastal navigation.
Here’s a chart that shows coverage.
http://en.wikipedia.org/wiki/File:World-loran-map.pngI was one of the many engineers who worked on the GPS satellite back in the late ’70s. The GPS chain can and will go down for a number of reasons. We’ve become so dependent on it that most folks can’t get home without it. Owners no longer prepare deviation cards for their compasses. Basic navigation equipment such as depthsounder and speed through water may be missing, inaccurate, or not working. They may not have the skill to get home even with the equipment. Even with these skills, operators might not really know where they are if the chain goes down. “Oh, I was following the GSP to Provincetown. I should be there in five hours, but I have no idea what my coordinates were were when the GPS stopped working. Please send out a coast-guard boat that I can follow home.”
Micrologic used to make a handheld unit that ran on batteries. You can still find them occasionally on ebay for short money. One of the nice things about this unit is that it will probably still work even if your boat gets hit by lightening. Its cheap insurance.
Regards
Rich
BlackSheep #47
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Er, ah, if you can only get within 20 miles with your sextant you probably shouldn't be using it as a primary means of navigation. You could very easily miss Bermuda altogether. Six miles is fair to middling and I know people who are within one mile most of the time. If you're headed to Europe or Africa, 20 miles is ok.
Here is the Naval Observatory's information on the current satellite status: http://tycho.usno.navy.mil/gpscurr.html you can check the status of the current groups. The newest ones were launched a this year and have a lifetime of seven or so years. The whole constellation seems to need replenishment every 10-15 years or so.
This summer I've seen the GPS go out for more than several minutes (once for almost an hour) at least three times. Made me wish I had cleaned my speedo…
Bob
Anyway, it pays to keep track of where you are…
Bob
On Wed, Sep 16, 2009 at 2:46 PM, < ([email][/email])> wrote:
Quote:Offshore is relative. I've been able to receive a fix to within about 20 miles of accuracy near Bermuda. That's better than nothing and about what you can expect with a sextant. This was done with a good LORAN, a Micrologic 9000S. Some of the less expensive units have a less sensitive receiver and won't provide a fix that far out. Even though offshore coverage is sketchy, its worth having a backup for coastal navigation.Here's a chart that shows coverage.
http://en.wikipedia.org/wiki/File:World-loran-map.pngI was one of the many engineers who worked on the GPS satellite back in the late '70s. The GPS chain can and will go down for a number of reasons. We've become so dependent on it that most folks can't get home without it. Owners no longer prepare deviation cards for their compasses. Basic navigation equipment such as depthsounder and speed through water may be missing, inaccurate, or not working. They may not have the skill to get home even with the equipment. Even with these skills, operators might not really know where they are if the chain goes down. “Oh, I was following the GSP to Provincetown. I should be there in five hours, but I have no idea what my coordinates were were when the GPS stopped working. Please send out a coast-guard boat that I can follow home.”
Micrologic used to make a handheld unit that ran on batteries. You can still find them occasionally on ebay for short money. One of the nice things about this unit is that it will probably still work even if your boat gets hit by lightening. Its cheap insurance.
Regards
Rich
BlackSheep #47
Original Message
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Actually, before GPS, getting within 20 nm of your position when approaching Bermuda was not all that bad if you were running a DR most of the way. Our Loran fix on the way to Bermuda was better than that, but we were probably just lucky. Now everyone drives right up to St. Davids following their GPS. In the 80s (I know more old fart lore) we used the Gibbs Hill Light and RDF beacon to approach the reefs from a safe direction. We did it at night on those races, but that was racing. Without GPS and cruising I would have waited until daylight.Â
Scary thinking about using an RDF bearing to approach reefs. A longer time ago I was approaching Cape May, NJ from about 50 nm off-shore and I wanted to get a RDF fix using the Cape Henlopen and Atlantic City beacons. The LOP from Atlantic City looked OK, but the Henlopen LOP put me somewhere on the Garden State Freeway.On Wed, Sep 16, 2009 at 3:02 PM, Robert Fine < ([email][/email])> wrote:
Quote:Er, ah, if you can only get within 20 miles with your sextant you probably shouldn't be using it as a primary means of navigation. You could very easily miss Bermuda altogether. Six miles is fair to middling and I know people who are within one mile most of the time. If you're headed to Europe or Africa, 20 miles is ok.Here is the Naval Observatory's information on the current satellite status: http://tycho.usno.navy.mil/gpscurr.html you can check the status of the current groups. The newest ones were launched a this year and have a lifetime of seven or so years. The whole constellation seems to need replenishment every 10-15 years or so.
This summer I've seen the GPS go out for more than several minutes (once for almost an hour) at least three times. Made me wish I had cleaned my speedo…
Bob
Anyway, it pays to keep track of where you are…
Bob
On Wed, Sep 16, 2009 at 2:46 PM, < ([email][/email])> wrote:
Quote:Offshore is relative. I've been able to receive a fix to within about 20 miles of accuracy near Bermuda. That's better than nothing and about what you can expect with a sextant. This was done with a good LORAN, a Micrologic 9000S. Some of the less expensive units have a less sensitive receiver and won't provide a fix that far out. Even though offshore coverage is sketchy, its worth having a backup for coastal navigation.Here's a chart that shows coverage.
http://en.wikipedia.org/wiki/File:World-loran-map.pngI was one of the many engineers who worked on the GPS satellite back in the late '70s. The GPS chain can and will go down for a number of reasons. We've become so dependent on it that most folks can't get home without it. Owners no longer prepare deviation cards for their compasses. Basic navigation equipment such as depthsounder and speed through water may be missing, inaccurate, or not working. They may not have the skill to get home even with the equipment. Even with these skills, operators might not really know where they are if the chain goes down. “Oh, I was following the GSP to Provincetown. I should be there in five hours, but I have no idea what my coordinates were were when the GPS stopped working. Please send out a coast-guard boat that I can follow home.”
Micrologic used to make a handheld unit that ran on batteries. You can still find them occasionally on ebay for short money. One of the nice things about this unit is that it will probably still work even if your boat gets hit by lightening. Its cheap insurance.
Regards
Rich
BlackSheep #47
Original Message
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That's pretty funny (probably scary at the time). My first sun sight off of Block Island, when reduced, put me just off Norfolk. Ah, I'm glad I had loran. Oh, and a sunny day.
Bob
On Wed, Sep 16, 2009 at 3:23 PM, John Stevenson < ([email][/email])> wrote:
Quote:Actually, before GPS, getting within 20 nm of your position when approaching Bermuda was not all that bad if you were running a DR most of the way. Our Loran fix on the way to Bermuda was better than that, but we were probably just lucky. Now everyone drives right up to St. Davids following their GPS. In the 80s (I know more old fart lore) we used the Gibbs Hill Light and RDF beacon to approach the reefs from a safe direction. We did it at night on those races, but that was racing. Without GPS and cruising I would have waited until daylight.Â
Scary thinking about using an RDF bearing to approach reefs. A longer time ago I was approaching Cape May, NJ from about 50 nm off-shore and I wanted to get a RDF fix using the Cape Henlopen and Atlantic City beacons. The LOP from Atlantic City looked OK, but the Henlopen LOP put me somewhere on the Garden State Freeway.On Wed, Sep 16, 2009 at 3:02 PM, Robert Fine < ([email][/email])> wrote:
Quote:Er, ah, if you can only get within 20 miles with your sextant you probably shouldn't be using it as a primary means of navigation. You could very easily miss Bermuda altogether. Six miles is fair to middling and I know people who are within one mile most of the time. If you're headed to Europe or Africa, 20 miles is ok.Here is the Naval Observatory's information on the current satellite status: http://tycho.usno.navy.mil/gpscurr.html you can check the status of the current groups. The newest ones were launched a this year and have a lifetime of seven or so years. The whole constellation seems to need replenishment every 10-15 years or so.
This summer I've seen the GPS go out for more than several minutes (once for almost an hour) at least three times. Made me wish I had cleaned my speedo…
Bob
Anyway, it pays to keep track of where you are…
Bob
On Wed, Sep 16, 2009 at 2:46 PM, < ([email][/email])> wrote:
Quote:Offshore is relative. I've been able to receive a fix to within about 20 miles of accuracy near Bermuda. That's better than nothing and about what you can expect with a sextant. This was done with a good LORAN, a Micrologic 9000S. Some of the less expensive units have a less sensitive receiver and won't provide a fix that far out. Even though offshore coverage is sketchy, its worth having a backup for coastal navigation.Here's a chart that shows coverage.
http://en.wikipedia.org/wiki/File:World-loran-map.pngI was one of the many engineers who worked on the GPS satellite back in the late '70s. The GPS chain can and will go down for a number of reasons. We've become so dependent on it that most folks can't get home without it. Owners no longer prepare deviation cards for their compasses. Basic navigation equipment such as depthsounder and speed through water may be missing, inaccurate, or not working. They may not have the skill to get home even with the equipment. Even with these skills, operators might not really know where they are if the chain goes down. “Oh, I was following the GSP to Provincetown. I should be there in five hours, but I have no idea what my coordinates were were when the GPS stopped working. Please send out a coast-guard boat that I can follow home.”
Micrologic used to make a handheld unit that ran on batteries. You can still find them occasionally on ebay for short money. One of the nice things about this unit is that it will probably still work even if your boat gets hit by lightening. Its cheap insurance.
Regards
Rich
BlackSheep #47
Original Message
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Rich,
Shooting from the deck of a small sailboat on the open sea, a decent sextant-generated fix is typically accurate at least to within 3 miles, and often much less, i.e., much closer to the true mark than that. A Loran “fix to within 20 miles of accuracy” isn’t a fix at all. It’s not even good DR. Or did I misread your sentence?
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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