Positional Accuracy
When you use the map you will find that some of the information does not always line up. The reason for this is how the information was created. There are many factors that go into creating map information, including funding. Generally speaking, the more funds an agency has at its disposal the more accurate development methods it can use.
For example, you may notice that some contours cross onto land. If the agency creating the contours performed on the water surveys the contours the positional accuracy would have been much better. However, that method is pretty expensive. It is much cheaper to draw the contours in a computer-based environment using other sources such as older hard copy maps. When this process is used it can introduce positional error to the data.
Other factors such as coordinate systems and data transformation play a role as well. We are not going to go into detail here as it is pretty boring and technical and we can’t imagine you really want to know it. But in brief, there are many mathematical computations to determine location on the globe. When different computations are applied to the data slight variations in position can occur.
Locations in the map are therefore generalized. The planning you do here will get you close to the area you need to fish. We cannot guarantee the absolute accuracy but we can bet you'll be within 10-15 feet. Generally speaking the imagery provides your most accurate base layer to mark positions with.
