Combining that with GPS
When you cap those features with GPS capability, you're really cooking! (Pardon the pun.)
Most fishfinders have the GPS antenna built-in, with the exception of a few models, like the Humminbird 1158c, which has an external antenna.
But before we get more into GPS, let's quickly talk about charting packages. Most gps fish finder combo units come with some sort of charting package pre-loaded, and they can usually be expanded with a memory card for better or more specific charts. Let's talk about some of the more common ones:
Basemap: Some units, such as this model of the Elite-5 by Lowrance, come with basemaps preloaded. As you can guess from the name, this is the most basic map - in the United States, most "basemap" units ship with a basemap of the United States - basemaps do not have any contour, depth, or extra data. You can just expect to see blue for water, brown/green for land.
ContourXD: ContourXD is Humminbird's version of a basemap. It covers 3,000 U.S. lakes, and shows depth contour lines, U.S. lights/markers, and interstate highways. This charting package is provided by Navionics - and is a pretty decent package, found on Humminbird 700, 800, and 1100 series models.
Navionics Gold: What I like to call the "king of charts", these charts can cover an entire continent, and still be able to zoom in down to 3 meters. They show tides and currents, port plans, depth contours, marine services contact information, and marsh areas. Navionics Gold charts are available on select Lowrance units, such as the HDS multi-function displays.
BlueChart g2 Vision: This is Garmin's answer to Navionics - BlueChart g2 Vision features auto-guidance technology, where you enter a waypoint and the charts will automatically search for the safest and fastest route customized to your boat size. You can also view satellite images of the bigger ports and shorelines, as well as a 3D view of the land and an underwater view as would be seen from the waterline.
Lowrance Lake Insight: These charts have incredibly detailed views of 650 lakes from the Midwest, with 1-3 foot contour data! As well as that, there are crowdsourced fishing hotspots on certain lakes, as well as contour and relief data for over 5,000 U.S. lakes.
Now that you are armed with GPS and your charts, there are a number of things you can do:
Get Navigational Data: The internal GPS can show your heading and average speed, as well as an ETA for your waypoint or destination.
Set Waypoints: You can save your favorite spots on your fish finder's charts as waypoints. A waypoint is like a "memory" on the whole chart. Next time you are on the same lake or river, you can just choose one of your saved waypoints and navigate straight to it.
Set Routes: A route is a collection of waypoints, from point A to B to C to however many points you want to go to! Routes are the most basic way of "true" navigation. Your fish finder will show your heading, and a suggested track to get to the waypoint.