I took a look at Aransas Pass. btw, I used to keep a boat at Mustang Island....Old stomping grounds
Anyway, the problem you see is real, and is a bug. The issue is that there are two cells of the same scale, one of which is entirely
contained within the outline of the other.
Our quilting algorithm fails in this case. Same thing going on at Tampa Bay.
Thinking about this some more, I conclude that this is yet one more of the more odd things about NOAA ENC
compilations. In this case, there is a "hole" in a chart cell of 1:20,000 scale, and in that "hole" should be another chart cell of 1:20,000.
Why are there separate cells if the scale is the same?
Up to some cartographer's judgment somewhere, I guess, related to the original cartographic data source. Anybody have any other reasonable explanation for this situation?
Anybody know of any other places where the same situation obtains?
Anyway, we can fix it of course. The fix will not appear in the upcoming Service
Release of OpenCPN V3.0.0. It should, however, appear in the 3.1 Beta series starting soon.
Meantime, if you really need the cells affected, you may run in non-quilted mode and select them individually.
Regarding your question of duplicate charts:
As the chart database is built, duplicates are identified, and the most recent Edition is selected for the database. So, there should not be any exact (i.e. filename) chart duplications in the database.
If you think you have found such a case, we would like to hear about it.