2 Garmins/2 Positions

[R29Sunshine]

I was out at anchor the other night....I set the anchor alarm on the left Garmin....and as the night went by, the winds shifted and I received an alarm. I initially looked at the left Garmin and I was still inside the area I had set....but the right garmin had me just outside the area. Are the two devices not synced together somehow to possibly average out a position ??

What should I do differently to avoid the discrepancy between devices?
Do I just need to turn one Garmin off when setting an anchor alarm or can the positions be pulled closer together some way by syncing them to get an average....?

Thanks,

Tim K.
R29Sunshine

 

[Submariner]

For us, the Garmin chartplotter uses about 27watts, so at anchor we shut it off to conserve power.

For an anchor alarm, I just got an app for my phone. There are plenty out there. (I went with Anchor Pro for an iphone). I just tell it "I'm anchored. If I leave 150' radius, wake me up".

 

[knotflying]

Ditto on Submariner.

 

[baz]

Ditto on knotflying.

 

[R29Sunshine]

LOL....got it!!! Getting the app.... 🙂

Now....how about the difference in position between the two Garmin devices....is that normal...?

Is there something I can do to get them more in alignment with one another??

Thanks again,

Tim K.
R29Sunshine

 

[baz]

LOL....got it!!! Getting the app.... 🙂

Now....how about the difference in position between the two Garmin devices....is that normal...?

Is there something I can do to get them more in alignment with one another??

Thanks again,

Tim K.
R29Sunshine

Is it a constant issue, or was it a one time event ?

 

[JamesTXSD]

I'm old enough to remember when GPS wasn't economically available. When I got that first GPS, I got some advice: if you want to know exactly where you are, get a GPS... if you want to know the general idea of where you are, get two GPSes. 😉

GPS is generally very accurate (within 9 meters). If the two GPS units do not utilize the same charting software, it is more likely that is where the discrepancy lies. Check the lat/lon on each and see if that agrees.

I have to chuckle when I see someone post: "My boat is in a narrow canal, and the GPS shows I am on land! How do I fix this?" Again, a charting error, not a malfunction of the GPS. If the area in question hasn't been surveyed in years (most often the case), the chartmakers are relying on dated info. That's why you have radar AND eyeballs. In spite of what some old salts will tell you about paper charts and a compass (yes, I remember those days, and then Loran C), GPS is still far more accurate than "the good ol' days." You still have to look out the windows.

I also have two GPS units in our motorhome (one built-in infotainment unit and a portable GPS), and they are occasionally a tiny bit off from each other. Nature of the technology and mapping software.

 

[Submariner]

LOL....got it!!! Getting the app.... 🙂

Now....how about the difference in position between the two Garmin devices....is that normal...?

Is there something I can do to get them more in alignment with one another??

Thanks again,

Tim K.
R29Sunshine

I once left my chartplotter in standby at the dock, moored. Came back the next day and the track it left had me +/- 50 feet around the boat, out in the channel next to my slip... I figured, what's the accuracy of GPS without the WAAS satellites? Garmin says it should be within 15 meters (49 feet). Also note, the tide goes up and down about 12ft. The track led me to believe the tide change also affected the track, which means it affected the GPS position. (Waas supposedly will improve accuracy down to less than 3meters, but I doubt I'd get waas signal sitting under cover at a marina in a slip).

15meters of accuracy on a boat that's 10 meters long. Good enough, but not precise.