"Len Krauss" wrote in message
...
Having a little problem with my chart display showing my position approx
150
ft west of actual, I checked chart datum (NOAA BSB raster type) and found
it was NAD83, whereas my GPS (non-WAAS) had been set to WGS84. So just for
the heck of it I set the GPS to NAD83. That didn't correct the position
error. From what I understand, WGS84 and NAD83 are practically identical,
so is there any reason not to just leave GPS set to WGS84 (this is in SW
Florida, USA)?

Any advice on what else to check to correct the westerly error would be
appreciated. (using Capn nav software and Garmin GPS 48).

Thanks,
Len

My Garmin 182C with the latest Blue Chip puts my boat exactly where it
should be in my marina. Right on the correct finger.
I recently bought Ozi Explorer and a friend gave me a set of older charts on
CD. With this set-up my boat is 150 yards too far North-East. I thought it
might be the datums but no other datum gave better results than WGS4. I
bought the latest paper chart for the area and plotted the L/L shown on the
laptop. Exactly correct on the new chart. So the old chart on the CD was
inaccurate by 150 yards in terms of the location of my marina. I imagine it
is more accurate for navigational hazards but it makes you wonder.