I am in need of a little help on my Humminbird 581i.It was on the boat I just purchased and while sitting in my driveway,in the boat and on the trailer the speed on the screen says 1.4 MPH.Is there a way to calibtrae this unit as I would think while sitting on a trailer, it should read 0 mph. Thanks in advance for any help.
you weren’t rolling downhill were you? 
Hi,
Are you “polaris-pete”? A member of Walleye Central posted the same question on that forum. The answer posted there is basically correct. Even though your boat may be sitting still in your driveway (as far as I know) the earth is still moving. Watch you GPS Status screen (you will have to enable it to be “viewed”), you will see satellites continually being picked up and dropped (signal strength(s) will also be changing). That is the way ALL GPS boxes work.
Take care,
Roger
Roger- yes same guy. I just find that there is alot more help on here than on some of the other forums. Thank you for the reply. PK
Nope don’t think so but at times I do have to wonder!!!!!!!!!!!!!
A friend had a speed issue on his bird, adding the external gps solved it.
Regarding the earth moving comment, it’s bogus. 3 lowrance units and a garmin in truck never give me a 1mph reading when I myself am stationary. Antenna issue.
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A friend had a speed issue on his bird, adding the external gps solved it.
Regarding the earth moving comment, it’s bogus. 3 lowrance units and a garmin in truck never give me a 1mph reading when I myself am stationary. Antenna issue.
Mark is correct, I’m the friend. Peter, go back on walleyecentral and read the post in the link that was posted.
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Hi,
Are you “polaris-pete”? A member of Walleye Central posted the same question on that forum. The answer posted there is basically correct. Even though your boat may be sitting still in your driveway (as far as I know) the earth is still moving. Watch you GPS Status screen (you will have to enable it to be “viewed”), you will see satellites continually being picked up and dropped (signal strength(s) will also be changing). That is the way ALL GPS boxes work.Take care,
Roger
That is a huge myth regarding GPS. They earth is moving, but not at 1.4MPH, it is moving at about 1000mph. So if it was picking up earth rotation, wouldnt it say 1000mph? GPS’s track your movement ON EARTH, they dont track the earth moving. GPS is a System that tracks your Position on the Globe. The satellites move with the earth in orbit.
This has been an ongoing issue with HB units that have internal GPS. You could get the external puck, or just be fine knowing that is the way it is. My 788ci reads fine once I get going above 2 mph. Perfect for regulating my trolling speed, which is usually never under 2 mph anyways. I just am aware of the issue and let it be.
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This has been an ongoing issue with HB units that have internal GPS. You could get the external puck, or just be fine knowing that is the way it is. My 788ci reads fine once I get going above 2 mph. Perfect for regulating my trolling speed, which is usually never under 2 mph anyways. I just am aware of the issue and let it be.
Just be fine with it the way it is? If everybody had that attitude companies would continue to put out products that don’t work properly, because people will buy them anyways.
Thanks again to all. It will have to be what it is with this unit..I just took my handeld Garmin GPS out in the baot and it to did the variations of .2-.4 MPH.
My Garmin hand held reads 0.0mph sitting still.
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My Garmin hand held reads 0.0mph sitting still.
As does mine.
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This has been an ongoing issue with HB units that have internal GPS. You could get the external puck, or just be fine knowing that is the way it is. My 788ci reads fine once I get going above 2 mph. Perfect for regulating my trolling speed, which is usually never under 2 mph anyways. I just am aware of the issue and let it be.
Just be fine with it the way it is? If everybody had that attitude companies would continue to put out products that don’t work properly, because people will buy them anyways.
Thanks for the advice on life Trav 
If I need any more advice I’ll be sure to ask. Until then
No problem 85Lund 
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