Electronic Charts - Need advice

[Paolaa]

We were sailing around Bahamas and we found that the Navionics charts were bad. When we arrived into Dominican Republic we dicovered that they were awfull. So we want to change into CMAP.

We saw Cmap NT+ and we think they have good details.
There is another one the Cmap MAX 11 , but we did not see them.

Does anyone know both?
What can you tell me?

[RichH]

Not the answer you wanted .... For the Bahamas the only valid/useful electronic charts are those based on "Explorer Charts" ... and do come preloaded in most newer Garmin plotters.

There is a forum of S57 charts on panbo.com ... and Forum Index - MacSailing.net - Powered by FusionBB which is mostly for MacENC, etc. charting systems but may uncover what youre looking for.

[hellosailor]

Awful? Does that mean, bad chart datum? Inaccurate? Lacking detail? Based on very old surveys?

And what do you expect from a competing product? The brand name won't buy you anything better, if the source data is the same and that's the problem. Or if the problem is from a local datum, which needs to be offset in every product.

[Minnewaska]

Lots of things move: shoals, nav aids, etc. Chart data rarely keeps up, especially in the Bahamas and Caribbean.

[Faster]

Electronic charts are usually based on the "official" charts, eg CHS in Canada, etc. We found in Mexico the charts were completely unreliable, often showing anchored a half mile or more inland - not the plotter's fault, but the fact that the charts available for it were based on long outdated, poorly surveyed Mexican govt charts.

Would anyone else's program be any better? I doubt that Ramarine, Cmap or whoever would want the liability of producing their own charts....

[svzephyr44]

Originally Posted by Faster

Electronic charts are usually based on the "official" charts, eg CHS in Canada, etc. We found in Mexico the charts were completely unreliable, often showing anchored a half mile or more inland - not the plotter's fault, but the fact that the charts available for it were based on long outdated, poorly surveyed ... charts.

As pointed out the underlying data for electronic charts can be quite old. Some Belize charts were surveyed in the 1890's and not updated since. As a general (or admiral) rule NGA (the people responsible for charts outside the US - their primary customer is the US Military) doesn't update detailed charts not of interest to military operations. The more you get off the beaten track the older the charts can be. It is also true that an approach chart for large ships (military and cruise ships) could be updated but all of the surrounding charts could be decades old. I too have found myself charted on land. There are Pacific Islands charted 10 or more miles from their actual location. This was not really discovered until GPS became prevalent.

The usual solution is to purchase a cruising guide (explorer charts being an example) of the area from someone who has made a post GPS survey. Frequently this will not get you a chart but will get you surveyed "safe" routes for passage.

[jackdale]

Another option is to forget using the GPS function. Use your chart and your eyes.

I have even used my raster charts and OpenCPN to do three bearing fixes.

[Paolaa]

Originally Posted by hellosailor

Awful? Does that mean, bad chart datum? Inaccurate? Lacking detail? Based on very old surveys?

The problem was
Bad chart datum - talking about depth. Instead , in Garmin it showed the real depth.
And we found they have not enough detail.

When we arrived at Dominican Republic there was not detail at all. Fortunatelly we were with another boats

As far we sailed we found less detail

[Lake Superior Sailor]

Sounds like an opportunity : Fill in the blanks !...Dale

[Faster]

Radar overlay really helps to show what errors are present in those suspect charts.. don't think I'd be making a landfall in the dark without radar in some of those areas....