boomerangben
Well-known member
Problem is finding a pilot who can fly to 1cm accuracy
1cm GPS accuracy? Not really on a boat but...
- Thread starter GHA
- Start date
wonkywinch
Well-known member
I remember telling an instructor I couldn't fly to an accuracy of 1 degree heading. He told me to turn left 5 degrees then turn right 4 degreesProblem is finding a pilot who can fly to 1cm accuracy
LittleSister
Well-known member
Not as far as I could ever work out. There is simply a fast/slow toggle, but it doesn't make anywhere near enough difference.
If anyone knows how you can change it significantly, I'd love to know. I can live with it, but it's annoying, and is presumably consuming unnecessary power, doing calculations every couple of seconds.
johnalison
Well-known member
Before GPS came Decca, which I first had in 1987 but first saw a few years earlier. I vaguely remember something called Satnav long before GPS that relied on moving satellites and I think was somewhat intermittent. Decca was brilliant, though it took about 20 mins to find itself, and accuracy varied from place to place. Generally it was about 50m but could be much worse in places like Beachy Head, where the position lines crossed at narrow angles. You had to tune to a station within range, which meant changing to the Dutch chain halfway across the North Sea, but this happened automatically. I used to play with it and try to get a position from the Northumbrian chain, which would give about 5 miles accuracy.
My first GPS was a handheld set by Magellan, with ‘landmarks’ instead of waypoints. I first used this in 1999 when Decca was phasing out, and it was of great assistance when entering Braye in 50-metre fog. Although the readings were subject to fluctuation, you could mentally average out what you seeing and be fairly confident of being accurate enough. Nowadays it is ridiculously accurate. I won’t say that it takes the fun out of it, but there is nothing to compare with the felling of being in the middle of nowhere and having only the vaguest notion of where you are.
LittleSister
Well-known member
I used to sometimes sail on a friend's boat that had some charts with the Decca lattice marked on it, but have never used the kit.
I first got a GPS, a handheld, in the (mid?) 90s, and would only use it when I was crossing e.g. Devon to Brittany. If I recall correctly it didn't have a map, just gave you a lat/long, which you could then mark on a paper chart. I would switch it on to get a fix about half way across, to check progress and that I wasn't way off track, then quickly turn it off again - it got through batteries (dry cell, not rechargeable) incredibly quickly. I'd then turn it on again briefly a couple of times as I closed the coast. (I think I'd only ever turned it on a small number of times when it finally expired after a few years, by which time the technology available at budget prices was transformed.)
As well as reducing uncertainty on long crossings, and avoiding the need to approach a coast before dawn to be sure from lighthouses where I was, I thought it a safety measure - if I ever had to put out a Mayday I'd be able to give an exact position, rather than a not very confident notion of roughly where I might be.
I first got a GPS, a handheld, in the (mid?) 90s, and would only use it when I was crossing e.g. Devon to Brittany. If I recall correctly it didn't have a map, just gave you a lat/long, which you could then mark on a paper chart. I would switch it on to get a fix about half way across, to check progress and that I wasn't way off track, then quickly turn it off again - it got through batteries (dry cell, not rechargeable) incredibly quickly. I'd then turn it on again briefly a couple of times as I closed the coast. (I think I'd only ever turned it on a small number of times when it finally expired after a few years, by which time the technology available at budget prices was transformed.)
As well as reducing uncertainty on long crossings, and avoiding the need to approach a coast before dawn to be sure from lighthouses where I was, I thought it a safety measure - if I ever had to put out a Mayday I'd be able to give an exact position, rather than a not very confident notion of roughly where I might be.
srm
Well-known member
Decca made navigation so much easier, even with its errors and areas of uncertainty. Speeded up plotting by entering the middle of a compass rose as a way point. Then plotted reciprocal bearing and range to waypoint.
Before that electronics for most of us amounted to hand held radio direction finders and flashing light echo sounders. I once made a fog landfall in Norway with a running fix on an RDF beacon transmitting at 6 minute intervals, then crossed the guestimated track with a depth contour when the echo sounder lost the bottom. Mentioned this during my YM exam and was told I could not do that as it was not accurate enough. No reply though when I asked what they would have done.
Used one like that. A year or so latter got an updated handheld GPS that had a basic track plotting function. It also had a 12v power cable and connector to a laptop so with some software from eBay I had a chart plotter.
Wansworth
Well-known member
East is least west is best!
B27
Well-known member
First GPS I had was a Magellan, it gave lat/long and stored a few dozen waypoints, so you had bearing and distance on a 'GOTO'. Mid 90s?
I still fall back to that in case of fog etc, I have a few key waypoints stored.
Many ports can be safely entered with just one or two waypoints.
I still fall back to that in case of fog etc, I have a few key waypoints stored.
Many ports can be safely entered with just one or two waypoints.
Farmer Piles
Well-known member
We have auto-steer GPS units on our tractors and they are accurate to about 30mm, RTK and farm based masts can make it even more accurate. We have had it when there was a NATO exercise in the Channel that the GPS went doolally - the Americans scrambling the domestic element.
The Q
Well-known member
I used to work on Tacan which was first used in the 1950s..
The Russians have been jamming GPS.. I was watching" flight radar" last Friday, and aircraft were shown approaching the Ukraine, then suddenly a 767 would do warp speed and change position almost 90 degrees and several hundred miles in a few seconds.
Don't depend on your gps if you near an American carrier or fleet either, the yanks jam local GPS..
The Russians have been jamming GPS.. I was watching" flight radar" last Friday, and aircraft were shown approaching the Ukraine, then suddenly a 767 would do warp speed and change position almost 90 degrees and several hundred miles in a few seconds.
Don't depend on your gps if you near an American carrier or fleet either, the yanks jam local GPS..
johnalison
Well-known member
I had RDF and although I practised with it often enough I don't think it ever really helped much. Before Decca, a typical Thames Estuary crossing would involve numerous detours to get close enough to the buoys to read their name/number, but post Decca and with GPS we can reasonably assume that each mark is what we expect it to be.
srm
Well-known member
I did my YM exam around 1980 in the Solent. One of the candidates for Coastal Skipper failed. In part because he did not go and check the name of a buoy that he was told could just be seen during a blind pilotage exercise.
GHA
Well-known member
and all this incredible accuracy reliant on so many discoveries about the patterns in the universe including Einstein figuring out time isn't the same for everyone, go really fast or be next to something really heavy your clock will not read be the same as another elsewhere.. both of which need to be factored in apparently. Not bad for a bunch of big brained monkeys!! Yet we don't really give it a second thought watching the little boat icon on a chart on a display..
onesea
Well-known member
Look for a function like smoothing or averaging. I normally go up to 15second to account for roll and pitch. On the basis that if I need a position more accurate I am doing it worng.
Dynamically Positioned ships actually have motion sensors to account for this and part of there set up is the location of each instrument relative to a set point. The a computer does clever stuff to work out where the ship is.
LittleSister
Well-known member
Oh, believe me, I did! If it's in there somewhere, I didn't find it. (I may have a fresh look again later.)
(Perhaps it's concealed with the function that allows one to have both current distance and CPA filters on the AIS alarm, rather than just one or the other.
)The Q
Well-known member
I too had RDF, which probably isn't a surprise as I was a radar Technician.. used it quite a lot in the Hebrides. Not too many buoys, but a fair amount of lighthouses I could get a fix on.
MADRIGAL
Active member
The last edition of the RIN's Navigation News quoted a report saying that aviators in the United States have been advised not to rely on GNSS for positioning owing to the the level of signal spoofing and jamming that has been detected.
Thistle
Well-known member
What's the difference between this and DGPS? Or is DGPS just this technology expanded to use a network of fixed base stations?.. the technology might be of interest to a small handful of people on here.
GHA
Well-known member
wonkywinch
Well-known member
Some clever bods have now produced a live GPS spoofing website so you can see where trouble lies -
Live GPS Spoofing Tracker Map
