Fish Finder with GPS: Maps, Waypoints and Combos

A fish finder with GPS is really two instruments in one box: the sonar that looks down, and a chartplotter that tracks where you are and remembers where the fish were. The confusing part is that GPS, self-made maps and preloaded charts are three different things sold under similar names. This page sorts them out and shows which combos put sonar and a map on one small-boat screen.

What does GPS add to a fish finder?

GPS turns a fish finder into a chartplotter: it shows your boat on a map, saves waypoints over spots, records tracks, and on most units builds its own depth-contour map as you drive. The sonar still looks straight down; the GPS answers where you are and how to get back.

The three everyday uses:

• Waypoints: drop a mark over a brush pile, drop-off or school and return to it exactly another day.
• Tracks: record your path and retrace it, or avoid crossing the same water twice.
• Self-made maps: many units log depth as you pass and draw contour lines, giving a detailed map of water no commercial chart covers.

Without GPS, every spot you find is lost when you leave. That is why GPS is the first upgrade most small-boat anglers add after basic sonar.

What is the difference between GPS and charts on a fish finder?

GPS is the positioning that saves spots; charts are preloaded map detail layered on top of it. A unit can have GPS and self-made contours but no detailed charts. This distinction trips up buyers, because marketing uses GPS and maps loosely.

If you fish lakes with no good published map, a unit that makes its own contours matters more than preloaded charts. If you fish big named reservoirs or coastal water, preloaded detail saves time. Many anglers use both: a preloaded chart as the base and self-made contours to fill the gaps.

Which mapping systems do the brands use?

Each brand has its own chart and contour system, and they are not interchangeable between units. Knowing the names stops you buying a chart card that will not load.

Garmin’s Quickdraw and Lowrance’s Genesis build contours with no subscription or map data, straight from the sonar as you drive. Preloaded charts come either built into the unit or on a card you add. Pick the ecosystem before the exact model, because the maps follow the brand.

Can a fish finder show sonar and a map at the same time?

Yes, any GPS combo with a screen of about 5 inches or larger splits between sonar and the map, and larger screens show sonar, down imaging and the map in three panes. This is exactly what the small-boat angler asking for down imaging and GPS maps together needs.

On a 4 inch screen a split is cramped, so one view usually fills the screen at a time. A 5 inch screen handles a two-pane split comfortably, and a 7 inch screen shows three panes without squinting. For a bass boat that wants down imaging on the left and the map on the right, a 7 inch combo is the practical floor.

The down imaging view itself is explained in side imaging vs down imaging, and how to read each pane is in how to read a fish finder.

Which GPS combos suit a small bass boat?

A 7 inch combo with CHIRP, down imaging, GPS and either self-made or preloaded maps covers a small bass boat without going to a networked system. The sweet spot balances a readable split screen against console space and price.

A single 7 inch combo at the console, or one at the bow and one at the console on a bigger rig, covers most small-boat fishing. How screen size, mounting and GPS fit a small hull is covered in fish finders for a small boat. The transducer that feeds all these views is in fish finder transducers.

Do you need a subscription or a phone for GPS?

No. The GPS works from satellites with no connection, no fee and no phone. Preloaded charts are included or bought once as a card, and self-made contour mapping is free.

A phone app is optional and only handles extras: transferring waypoints between units, sharing maps, or registering the product. The core job, showing your position and saving spots, runs entirely on the unit. Treat any app as a convenience, not a requirement.

How does self-made contour mapping work?

As you drive, the unit logs depth against GPS position and draws contour lines, building a detailed map of the bottom with no commercial chart data. Garmin calls this Quickdraw Contours, Lowrance calls it Genesis Live, and Humminbird calls it AutoChart Live.

The map builds in real time at one-foot contour intervals on most systems, so a few passes over a spot reveal the drop-offs, humps and channels. It works on any water the boat covers, which makes it invaluable on small or private lakes that no published chart details. The data saves to a card and, on some systems, uploads to a community map others can use.

Self-made mapping needs no subscription and runs from the sonar you already have. It is often more useful to a small-boat angler than preloaded charts, because the spots you fish most become mapped in the detail that matters to you.

How many waypoints and tracks can a GPS unit save?

Entry GPS fish finders typically save thousands of waypoints and dozens of tracks, far more than most anglers ever use. The exact numbers vary by model, but capacity is rarely the limit.

Waypoints and tracks transfer between units through a memory card or a phone app, so you can carry your spots to a new finder or share them. Treat the card as a backup, because losing a unit over the side should not mean losing years of marked spots. For picking the right screen size to show all this on a small boat, see fish finders for a small boat.

Who does not need a GPS fish finder?

Bank anglers, rental-boat users and anyone fishing one small familiar pond can skip GPS and save money. If you never need to find a spot again or navigate back, the chartplotter adds cost you will not use.

Castable and very small portable units also often lack useful GPS, and that is fine for their job of a quick look under the boat or through the ice. Those units are covered in portable and castable fish finders. For everyone fishing varied water and wanting to return to spots, GPS is worth the step up.