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My latest Lowrance unit shows my location roughly 80 yards west southwest of actual. Is there any way to correct this?

How are you calculating the amount of error? If it's against a map be sure that the datum on your GPS is set the same as that noted on the map.

Results are the same for built-in Lowrance mapping and for Lake Master chip. Guestimating error amount based on distance shown from known point (rock, bouy, etc) to point shown on gps as current location. Trails consistently show boat crossing islands, rock piles, etc. well away from actual path.

Can you be more specific about how to check or correct....

Having a mismatch between the datum on a paper map and the coordinates given by your GPS might give the amount of error you're seeing but I don't believe that there's anything that can be done to correct the error for maps displayed on your GPS. Hopefully someone who owns a similar GPS might be able to comment furhter.

Datums are explained briefly here.

Realizing that the existing gps system can have varying amounts of error up to as much as I'm experiencing, it seems very strange that that amount of error can be built into a unit with no ability to correct it. I'm using it primarily on Lake of the Woods, Ontario. To be shown 80 yards away from a known rockpile just below the surface of the water, while I'm in fact on top (or imbedded in) it is not acceptable. Lowrance customer service should be an answer, but this is the real world, and they haven't heard of the term. My Lowrance experience goes back to the Green Box, and I've had about 15 units over the years. Time to find a new brand, I guess, as the lack of quality has been exceeded by poor-to-non-existent service.

PM

This is not limited to Lowrance as I see this type of error on Garmin's TopoCanada product too. 1:50000 topo maps in Canada are a mixture of NAD27 and NAD83 datums and somewhere during the conversion to digital mapping errors appeared.

So the Lowrance built-in map and the $150 Lake Master Canadian map are both equally bad? What a revolting development this is...!

Does anyone make a product that is more accurate?

PM