No matter how accurate your GPS lon/lat fix, it will never improve the accuracy of the underlying chart that you use. In some areas (like my home port) that charts seem to be highly accurate. In other areas (BVI) the charts can be off by as much as 0.5 nm, depending on which "chip" you purchase or charts you select (NOAA inaccurate, NGA accurate). I've posted many demonstrations of this before, but don't have time to hunt them down right now.
Originally Posted by Alex W
...For about the same price as the external NMEA 2000 GPS sensor you could buy a tablet that would give you a remote display from the A67 that is usable below decks. Any Android or iOS tablet will do it.
...or smartphone or Win8 tablet.
FYI, the Lenovo Miix 8" tablet that I have purchased (with internal GPS chip) has been seeing periodic price drops to $200 on Amazon. Just install OpenCPN, download NOAA's charts (preferably onto a 32GB microSD card), and install/configure GeolocationTCP
, and you've got a really nice portable chartplotter for US use: