Gd 1900c chart plotter



Have a problem I'm trying to work out on my chart plotter. I have verified that the vessel position is accurate, but if I enter a waypoint it appears to be about 200 yards off. The position data of the waypoint is correct, but the position of the waypoint is wrong.
Chart offset offsets the vessel position and the waypoint.
GPS offset makes the position data wrong.

Any suggestions.
Sounds like you are inputting the wrong GPS format type for your waypoints.
Lat/Lon can be in different formats like DD.DD.DDD,, DD.MMM.SS.S etc...
Make sure your points are in the same format as being used by your plotter.
The error looks a bit too large, but is it possible that it's caused by mixing WGS84 and NAD27 coordinates?

Another possibility is that your waypoint coordinate has been truncated. 0.1 min of latitude equals almost exactly 200 yards.
Thanks all. I had insured the entry format is identical, yes this added to the error until this was addressed. As far as WGS84 and NAD27, had not run across this option so will check.
Again, I am using Coastal Explorer with a GPS pod and live position data agrees exactly, even with inavX on my tablet. Taking the same lat/Lon numbers and entering those as a way point, this WP is off by about 200 yds. Cursor over the indicated way point shows different lat/Lon than the numbers I entered. Repeating the same steps on Coastal Explorer and inavX places the WP correctly which matches the live position.
Geold96........Where do I check for the WGS84 and NAD27 as you brought up?
What I wish to do is load my Route data so both my chart plotter, and related radar, auto nav all can be working together. It would seem now that when I do get the cable for data download, all the WP's will be off by the same error.

Thanks for the feedback, I have had this boat for 3years and always used the cursor to plot my course, so never was able to detect this error. I now am running predicted log contests Sotheby's blind turns made me dive deeper into the nav system on the boat, which I love and has done well so far.

My comment concerning NAD27 and WGS84 was a general observation on possible causes of position mismatches. In Southern California where I believe you are, the offset from NAD27 to NAD83/WGS84 will be equivalent to approx. -83m in longitude and +3m in latitude. As this is different to the error you see, it’s unlikely to be the cause. However when analysing position errors, it’s always useful to know the direction as well as the scale. In your case, is the waypoint error constant or does another waypoint say 50 miles away show a different error?

I am not particularly familiar with the 1900c, however the user manual shows an option to apply latitude and longitude offsets (see: 5.7.2)
On assumption that your charts are referenced to WGS84, is it possible that the GPS receiver is configured to output in a datum other than WGS84 and a previous owner has corrected for this by applying latitude and longitude offsets? This configuration may well plot your vessel in the correct position on the chart but put entered waypoints in the wrong place.
Good points and will follow up. So far, when looking at GPS offsets (currently set at o) it adversely effects live position. Chart offsets will do the same thing. My predicted log contest is tomorrow so will get back into this after the event, appreciate the input.