GPS positioning matching base map

[bmar444]

I am running an HDS-7 Gen-1 on my boat and have a 2009 LakeMaster chip. Problem I am finding is that my location rarely if ever matches up to the contour lines and it is not even close. I can run perpendicular to the contour lines and it can be 50 - 100 ft, before I reach the depth change.

Any ideas?

[3M TA3]

2 ideas. Have you added any keel offset and is the lake short on water this year. Water levels can sometimes change significantly over the course of the year. Also, I haven't ever seen any map that was right on, ever. Close but not on the money.

[bmar444]

So here's another perspective. Say you are out in 30 fow and you are trying to find that hump in the middle of the lake that comes up to 12 fow... not very accurate on finding this break. Sometimes off by 50 ft or more.

[Fastcat]

Go to a sporting goods store (Cabela's) and check out some of the Navionics chips on the demo units. Some maps are better than others, I have 3 chips for my area and use each for a different area of the lake depending on the area fishing. When I had my Lowrance HDS8 the lakemaster chip for Michigan was not very good compared to the Gold and Platinum ones I had, now the Lakemaster in my Hummingbirds are superior to the the Navionics on 80%the of the lake. I think you just need a chip upgrade, but go check them out for yourself first.


For kicks and grins, does this happen say at the dock? In other words is it the units gps thats off or the map? My guess is the map, but you never know I guess.