Obviously a bit of a newbie at this but I was looking at a chart of the other day and noticed a lot of three digit numbers in parentheses. What do the numbers mean?
It seems to be part of a grid but then, what is the grid?
I'm not entirely sure, but If I had to guess, I'd say they are Tract numbers (oil drilling leases) or something similar. Is the image from offshore in the Gulf of Mexico?
If I had to hazard a guess, I believe that's an Iphone (or similar) and the little pink ducks means that the map is overzoomed. It might be one of the Navionics Apps, but I'm not sure about that one.
Also, if you go to the Navionics website (go to Products > WebApp) you will see the grid and the bird icons. Just adjust zoom until they appear. I am looking at the gulf side of the lower part of Florida.
I believe the numbers in parenthesis are marking the quandrant. I'm not familiar with that marking on standard charts. I looked at ALL my paper charts and none of them have them. In your screenshot, notice there is only 1 per box and they are in numberic order going from left to right?
I'd say that is a function of the app your using and not a charting concept.
![photo[2].jpg](https://forums.iboats.com/data/attachments/150/150087-7b02ca617ad3189d5af8356a30d63f49.jpg "photo[2].jpg")
