I have an e7d MFD that shows SOG of 0.2 to 0.9 knots even when tied up in the marina. Latest Aug 2014 software with 5Hz GPS refresh speeds and medium damping. MFD is mouned in the cockpit with a clear view of the sky. While the Raymarine technical support has been awesome, I am skeptical about the corporate line that this is normal etc. An older Garmin 276C mounted below decks appears to give much better readings and does indeed show zero knots when stationary. The drift and course info is much more reliable and accurate when I use the older instrument than when I use the new e7d.
I posted my observations on the Raymarine site noting that others had observed the same thing. One suggestion is that the GPS sensor may be defective and that I can return the unit for warranty repair. Living on the north side of the 49th parallel makes this a probelmatic issue what with customs and duties - I am reluctant to ship it off again after the experience of a previous repair.
Has anyone else expereinced the same issue?
Can you plot your position and track? Position errors are well documented and explained. http://www.wirelessdictionary.com/Wireless-Dictionary-GPS-Errors-Definition.html
The error in position is random you'll see a wandering path in a somewhat circular.
http://home.earthlink.net/~cwkelley/gpsrftest.htm
Those errors mean phantom speed and direction readings.
The GPS works flawlessly and I am well aware of the errors inherrant in the system. However if an older Garmin 276C can deduce a speed of zero when moored why can't the more modern and allegedly sophisticated Raymarine e7d?
The e7d generally shows an HDOP OF 0.9 AND IMHOP should be able to figure out when the vessel is stopped. Could there be some merrit to the suggestion that the e7d GPS chipset is a dumbed down version since elevation calculations are not required??
The issue is merely an annoyance but since I sail in low wind conditions with tidal currents of up to 3 knots it would be nice to have an accurate SOG so that set and drift become meaningful.
What are the update frequencies of the 2 units? I have a similar issue with my Garmin 19x which has a fast update and reads all over the place, short-term, and an old (slow update) Micrologic 250 which reads more stable numbers. The Raymarine unit may average to zero, but since it only reads positive numbers you don't see it.
Hi Ian,
The Raymarine e7d has a 5 Hz update rate..... the old Garmin updates slowly perhaps once a second. Your 19x can be configured for slower updates and you may be able to apply damping in your chatplotter to effectively average your position.
I have played with the damping on the e7d and while it does improve things it still shows SOG as noted in the original post.
I was out sailing for 2 days this weekend and I was able to compare the two GPS receivers. The old Garmin 276C did a much better job overall and the set and drift numbers were very close to the tide/current tables for the area. The e7d GPS receiver on the other hand showed wide variations in set and drift numbers that point at poor SOG calculations by the unit.
Tony,
I concur with your observations. The upgrades to Lighthouse versions 10 and 11 on my e7D show much larger variations in SOG than previously even when filtered. Also, the cold start time to fix is now several minutes longer than before.
I guess that this is a case of one step forward... two steps back. The e7d is a great unit and the Lighthouse software is really slick. Does it just need a better GPS receiver? It is a little late for buyers remorse, I am getting used to the system but surely Raymarine can do better. I plan to try two other GPS sensors from Standard Horizon to see if I get better results. More later.
Jon, if you have the capability, can you try feeding the e7d with another GPS via NMEA 0183 or N2K?
Tony,
I doubt that it's the e7D's internal GPS since it did work better for me with previous Lighthouse releases.
I have hooked up one of the e7D's NMEA 0183 inputs to a Furuno GP-32 which gives better accuracy (it has an external GPS antenna) and shortens the cold start time. However the e7D occasionally looses this signal and issues fix alarms. I have not found the cause yet but suspect it's in my multiplexer wiring and not the e7D.
You may be able to get better results by adding an external GPS but I would wait to see what future software releases from Raymarine bring.
Hi Jon,
Thank you for confirming that you also get better results with an external GPS receiver. I am currently operating the system with the external Garmin 276C and I will post the results of my upcomming experiment with two other external GPS sources.
The aim is to get the best results for drift and set which requires accurate SOG - the e7d appears to have an issue with this. FYI I have left the unit running for several days with the internal GPS on and the track enabled. The resulting track furball is only about 10m in diameter which indicates very good position accuracy. A comparative test using the external GPS showed the same result. The big difference is that the external GPS always shows SOG as zero whereas the e7d does not.
So.... the problem is likely in the e7d internal software (Lighthouse) which is likely an easy update fix away. To further complicate my life I have just downloaded Lighthouse version 6.27 (the oldest version avaiable from Raymarine)and I will see how that performs.
I tried the previous software release and there was not really any difference in SOG performance, both stationary and moving. The external GPS receivers always give better performance. In order to get a better idea as to what was happening, I set up a simple test on the beach (see www.exotek.ca/Panbo) and compared the three units (full sky view, stable power etc.). The e7d was definitely the slowest of the bunch in aquiring a fix from a cold start. Not surprisingly, the other two units showed a SOG of 0.0 knots after several minutes, the e7d continued to show phantom speeds (between 0.2 and 0.9 kts.) even when the HDOP settled in below 1.0.
I went to the local Raymarine dealer and they pooh-pooh'd my concerns stating that when the vessel speed was greater than 0.5kts, the the error would not matter. My experience in comparing the internal GPS to an external one is contrary to their opinion. I demonstrated the problem on their display units.
While not a scientific test, I did note that their display e7d had the same issue as mine whereas one of the larger e Series units settled in nicely at 0.1 kts. This was indoors so not a good test. Meanwhile my smart phone GPS happily showed a zero speed.
I guess that I simply have to bite the bullet and call the unit defective and ship it back for repair/replacement :-(
After much to and fro, the unit was replaced and now all is well.