Before I make a substantial diagnosis attempt, was wondering if others have experienced this issue ...
On each of Friday 12th (around 11pm), and Saturday 14th (around 8pm), I experienced my Raymarine e-series / GPS combination errantly giving me a position that was 50 or more feet from the actual. On Sunday 8th it was showing my position about 50 feet South of my actual. On Saturday 14th it was showing me 80 feet west of actual. On that Saturday I went to the GPS screen and verified I had enough sat's and everything appeared fine (7+ sats with strong signal, HDOP = 1.0)
I am certain earlier on both days, the GPS was accurate +/- 10 feet or better earlier in the day, as I have a rather narrow channel I traverse that would make GPS errors apparent.
When I experienced inaccuracies last year I determined the equipment was fine, since I had my Garmin handheld handy and had the identical (incorrect) coordinates appearing on the Garmin and Raymarine. For the same time period, at least one person on Panbo reporting they had no GPS signal, and a light discussion on extreme sunspot activity being the cause.
Before I make a substantial diagnosis attempt, was wondering if others have experienced this issue last weekend.
I assume the errors were temporary. Was WAAS operational on those dates? Do you enable WAAS on your MFD?
If not WAAS I can only conclude the USAF may have been performing some unscheduled bird maintenance on those days?
Butch
Yes, temporary. Earlier on both days the position accuracy was within 10 feet or better.
WAAS enabled.
Let's add Wed Aug 19th 9pm EST to the list. Showed me 50 feet east of where I actually was. Again over land while I was actually in 23 feet of water.
Dan, When you say 'actual' position - relative to what? Without understanding your reference is it possible these may be chart errors? We have become very dependent on gps - so we do not usually have a more accurate reference that we can hang a hat on.
Brian
Maybe I should just say your mfd is shifting the chart 50 ft. Brian
Dan,
It's clear it's not the equipment nor the mapping software. The temporary nature of the fault must be attributed to the satellites or the sun. I have no ides how to check for sun spot or storm activity but I'm sure there is a site out there that reports such information. As to satellite problems I believe the US Air Force controls the satellites and performs the maintenance on them to include data error corrections. Perhaps a search for NORAD or US Space Command would point to a site with satellite operational information. If I can get a little time I'll do some checking, too.
When you figure this out please let us know what was going on.
Dan, could you leave Tracking on and see if it jumps to a new position when this happens? It would be interesting to see the typical scatter from your stationary position and then perhaps a new scatter from a temporary fixed "wrong" position or positions. Since each point recorded in a track is logged we may see when and how long the position shifted, whether it was a drift or jump and when it returned to where it started.
Of course this may also explain the variable buoys in Camden Harbor.
Doug
GPS only claims 3-6m accuracy 95% of the time.
50ft is fine for marine navigation, in fact go back to the bad old days of SA and 100m was good enough to find a harbour in poor vis and navigate in using pilotage. But 50ft off is a bummer for car sat nav.
PS: Thought WAAS was partially offline over continental US due to one of the two WAAS sats failing earlier this summer. I find the errors more consistant with WAAS/EGNOS switched off.
Took some time Saturday to look at this closely, didn't learn anything.
First I got my Garmin handheld, found that my garmin handheld matches my raymarine. Checked three times during the day. Also checked that WAAS was active.
Second I left the track on for four hours while my boat was at the dock. The position on the charplotter was where I expected it to be before and after, and I saw little movement.
Third, I got a memory card into my Raymarine so I can take some screen captures. But everything appeared ok, no boat out of water / over land screen captures to take.
Next time the position is out of whack I will repeat.
Did some diagnosis, didn't find anything wrong. Verified with a handheld I am getting the identical position as my boat mounted GPS.
Brian - Looking past the chart itself, verified specific bouys have different coordinates on different days.
Doug - Used the tracking feature for three hours at a time, twice. Negligable drift and scatter. Probably worth repeating for a longer period of time.
OceanFroggie - Sure, given the range of inconsistency, it's possible the GPS signal is fine and the WAAS signal is the source of inaccuracy.
Not sure I am going to investigate this anymore since multiple pieces of equipment give the same result.