Creating your own personalized mapping on your favorite fishing hole is easier than you might think. Plus, you’ll have exclusive details that might put you ahead of
the competition—and the fish.
April 17, 2025
By Thomas Allen
There was a day when simple mapping—to the tune of 5- or 10-foot contours at best—were feared to be the downfall of modern fishing. The technology certainly shortened the learning curve and made staying on fish and replicating patterns much easier. Gone were the days of triangulating your position between the green pontoon by the tattered red-and-white-striped boat-lift cover with the tilted weeping willow on the secondary lake point. Now, it’s all digital and at your fingertips.
Funny thing is, we’re still fishing today, and most fisheries seem to be as good as they’ve ever been. However, even in a world of rapidly advancing technology, mapping still reigns supreme on many levels. Yet, there are countless fisheries across the country, especially in our neck of the Minnesota woods, where mapping is far from perfect—frankly, it’s poor on some lakes. It seems the best lakes full of the dumbest fish have the least-accurate mapping. By design, perhaps? Those kinds of lakes need to stay secret.
By investing in a little steering-wheel time and a full tank of petrol, you can generate your own highly detailed contour map to really dial in on the spot-on-the-spot. For the sake of our discussion, I’ll be referring to this technology as custom mapping that applies across the board with recognized freshwater brands of fishing electronics including Lowrance C-MAP Genesis , Garmin Quickdraw Contours , Navionics SonarChart Live , and Humminbird AutoChart Live .
Why Make a Map? At first, a single pass doesn’t seem to make much sense, but after you make several passes with overlapping tracks, the map will begin to reveal details you were hoping to acquire. Subsurface cartography is far from proprietary, although some brands do own portions of the technology and processes unique to their independent devices, so you’ll definitely find variations between the flavors of chartplotters. Some brands purchased contour maps from other companies only to build and improve on what existed, and some import custom mapping created by independent customers. Most have numbers of teams running numbers of boats rigged to scan tremendous amounts of water—it’s a full-time job.
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However, even with the objective and technology, there are still missed details in every map—subtle details that could put you on a mega wad of your targeted species. Consider a lake you’ve fished for years. There are indeed spots that very few anglers know the intricacies of, such as how a secondary point lines up with an inside turn, or exactly how sharp a weedline or river channel drops into the depths. Your time spent on those spots makes you an expert; now consider making an exclusive map of your favorite spots with enhanced detail and precision. The ability to zero in on accurate contours , identify bottom hardness, vegetation, and more only adds to the fish-locating equation.
Even on very popular and heavily fished lakes such as Guntersville, Lanier, Fork, the Great Lakes, among others, there are countless areas within those lakes that feature accurate readings but with plenty room for improvement. And don’t feel like you need to map every inch of every lake—it’s more important to focus on smaller spots to dial in critical details.
“Mapping interior lakes and reservoirs and coastal waters is a never-ending job,” says Tom Schultz, GIS Manager at Humminbird’s LakeMaster Mapping. “We have teams of boats on the water every day working to establish and provide the best detail within our mapping solutions. But there are certain spots on certain lakes that don’t indicate the full detail. There are times when an angler’s eye is key to seeing what additional data are needed for full detail. That’s when our AutoChart Live comes in very handy.”
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Schultz said the secret to getting the most out of your map-making process is to scan the area multiple times at consistent speeds, but not to overdo it, as too much data dilutes accuracy.
“I suggest keeping your boat at 4 to 5 mph to maximize your readings,” he says. “Making grid-like perpendicular passes at 50-foot intervals helps establish impressive detail on a lucrative spot-on-the-spot. Those data are plugged into an algorithm within the Humminbird graph and relayed onto the LakeMaster mapping interface to provide a custom map. It’s really amazing technology.”
Gridding the area not only covers all the nooks and crannies of the spot you’re graphing, it also enhances the details to fully take advantage of 1-foot contours. Give yourself 40 to 50 feet between tracks as the technology does read out to the side. Having a personalized map is critical to zeroing in on specific details in regard to a hump, ledge, point or any type of fish-holding structure. Plus, just like any sort of fishing application or presentation, the only way to get the most out of your efforts is seat time—the same applies to mapping.
“Don’t let yourself get overwhelmed with excess mapping,” he says. “Start with a few spots and build from there. Sometimes, a personalized look at a few locations might indicate a finite detail that was originally overlooked, and with experience you can begin to find potential details that other anglers may not so easily identify—again, time on the water is the ticket.
“Just be aware the units themselves don’t usually offer enough data storage for extensive mapping; an external storage device is necessary to manage large amounts of data. For example, LakeMaster’s Zero Line cards offer more storage than you’ll likely use. Beyond that, back up your data, waypoints included, on an external hard drive or additional SD cards.”
Don’t Over Scan “Another thing to consider is to not run the scanning technology when the boat is taking off or on plane,” Schultz continues. “I suggest scanning your targeted area and then shutting down scanning when moving to another location, sometimes an overlap in data at speed reduces the accuracy of your scanned areas. To maximize map production, there’s an element of being thorough, but not overly thorough. Leave a little breathing room between passes and you’ll have the most accurate mapping available.”
Settings to Consider While you’re sitting in your captain’s chair, spend some time looking through and working with the settings. Therein lies the power to maximize your mapping efforts. There are various settings adjustments to make, as with most technologies, but for mapping it comes down to where you save the data and an assortment of color palettes to choose from. Sometimes it’s worth considering a contrasting color palette to the color you may have selected on your general mapping; the color change will help draw your eyes to subtle differences that may deserve an extra cast or two.
There’s a setting adjustment in the AutoChart Live program called Max Range that’s worth playing with. As you cycle through the numbers or adjust down to a number that best fits the lakes you’re fishing, a newly created lake map will come to life with a few mild tweaks. In other words, if you don’t plan to fish any deeper that 18 to 23 feet, for example, maybe drop the Max Range down to 23 or 24 feet and you’ll see the depth shadings adjust to draw your attention.
I can’t overemphasize how important a contrasting color palette is when it comes to finding sneaky little spots that often get overlooked.
You can also change the Contour Intervals inside the AC Live options menu. By clicking into this section, you can adjust the intervals to be separated by a single foot to fully maximize the details of the area you intend to fish. You can’t put a price on these data. There are other adjustments to consider within those menu options, and that will take time on the water and extra experimentation.
Once you’ve covered all the angles and created an accurate map, you need to go back and fish it. Chances are good you’ll find some important details that nobody else knows about. Become a Map Maker “The technology is baked into the chartplotter,” Schultz says. “The secret is how you use it and where. An exclusive map, especially the kind generated on a lake that could use updated scanning, is a powerful tool for anglers looking to get an edge on the competition and catching more fish. Keep your efforts guarded and you’ll be the angler to beat most days.”
