To get a very high details map you need 2 things:1st: update youre Elite so you will be getting all the capabilities of the Navionics card and get a Navionics+ so you will benefit of the soanrchart: 1ft contour
If you want to see how it looks, get on that page and zoom in until the blue button on the left bottom corner is active and cllck on it.
http://webapp.navionics.com/?lang=en#@6&key=erqgGjmfrM