Position error - boat icon location not accurate


A customer of mine has a Dell laptop running the latest Coastal Explorer. The boat icon on the laptop is off by about 50 feet, compared to the Garmin plotter where the GPS data is coming from, and also just by looking out the window.

The lat/lon numbers match EXCTLY between the Garmin and the laptop. Yet, the boat icon on C.E. is about 50’ to the east, compared to the Garmin, and the view out the pilothouse window. Also, other boats on AIS are showing on land, when they are actually in the water in the first slip in the marina. Raster and Vector charts both have this issue. It is like the chart is shifted about 50’ to the west. Any suggestions?

This happens with both a Keyspan serial to USB converter, and an Actisense NGT1 N2K to USB converter.

I have only observed this while the boat is stationary in it’s slip. I have not been out on the boat while underway to see if this error goes away when the boat is moving.

I have pictures but cannot see how to attach them.


You can attach pictures here with copy and paste, by dragging them into a message you are editing, or by clicking on the Upload button at the top of the message editor:

It would be impossible to say what’s going on here with any certainty without more information (and possibly the pictures). However, given that both your own vessel and AIS vessels are appearing in offset locations, it sounds like the problem is not with the placement of the vessel icons, but with the location of the charts.

The only thing that should cause that would be using charts that are too small scale for the scale at which you are viewing them. If this is the case, you should see an “overscale” warning near the bottom of the chart where the viewing scale is displayed. If this is the case, then it’s possible you don’t have a complete set of charts for the area you are looking at, or that a detailed chart hasn’t been created for that area.