Maps and charts for your GPS unit

I hear that many of you received new GPS unit from Santa. About this time you have probably installed the unit in your boat and maybe even tried it out.

I also believe some of you are not satisfied with the internal mapping images in your unit, as I have already received several requests that have expressed this very topic.

Most ask how to upgrade the images they see on the GPS screens and why wasn’t better mapping included in the unit?

Yes, I know some of you received GPS units preloaded with very good mapping images. You are the lucky ones. It shows what Santa really thinks of you.

But the rest of the units only have a primitive mapping system.

Why aren’t detailed maps included with the unit? I believe that part of the answer is “sticker shock.”

I believe most of the GPS manufacturing companies install a “base map” in their units as a means of getting you out with your unit. This base map is what the name implies: a basic map that probably can be used in the entire United States.

These base maps can produce maps from California to Maine, and of course includes Louisiana. This is because that the details of the area of coverage is really not what you would expect and requires very little memory compared to maps and charts that depict the images.

However, these images do not usually include the many, many bayous, lagoons, bays, rivers, canals and lakes that make up our marshes and fishing areas. In fact, some of the base maps do not even show some small towns and roads and many of the actual rivers, etc.

I believe this base-map configuration is a way of keeping the selling price down to a minimum, so as not to scare away buyers.

The top sellers of consumer GPS Combo units — Humminbird, Lowrance, RayMarine and Garmin — offer outstanding consumer combo GPS chart plotter/depth finder units. All will give you a very accurate GPS.

All will be able to deliver accurate positions to within 3 meters with the WAAS feature enabled.

Of course, the cost is also determined by the size of the screen and some other software, and if it can take a memory card and link to other units or a computer.

If your unit can accept supplemental mapping, and some units cannot, the crux of the dilemma is determining if the internal or accessory mapping will meet your particular mapping needs, exactly what kind of mapping you need or want, and the price of this add on feature. It is usually a feature vs. price matter.

I have seen some users who purchased a new GPS chartplotter and are totally dissatisfied with the internal mapping, and then learn that they cannot supplement the mapping or even update it with a download from the manufacturer.

So now you probably realize that you must get a supplemental mapping program for your unit.

As to the type of mapping software, I prefer in internal and/or accessory map programs that are based on USGS topographical maps rather than NOAA marine charts for my fishing needs in the coastal Louisiana marshes. Ortho (corrected) aerial photo maps that have corrected datum irregularities are a plus.

But remember that these are all only electronic images. They can be distorted or erased by a number of conditions. Always, always bring a decent hard-copy map for the area.

Yes, I know, NOAA marine charts are the best in the world for depicting the established commercial marine channels etc. These waterways are the ones marked with aids to navigation (NAVAIDS) consisting of lights, buoys, cans, nuns and day markers. However, I find this type of mapping lacking in showing the land, bayou, lagoon, lake and bays away from these marked channels.

Some of the manufacturers do not offer any thing other than NOAA chart-type mapping. Some units can only accept their own manufacturer’s version of mapping, while others can accept after market mapping programs such as Navionics, etc.

So the bottom line is check the mapping. Take time to note the type of mapping available for the GPS you intend to purchase or have, and see if mapping software for that unit will suit your needs.

I suggest that you visit a stocking GPS dealer and actually view the units that are available but, more important, actually view the mapping software available for that unit.

I have even found that many new purchasers first select the mapping software they want and then match its availability to a GPS unit that will suit their needs.

NOAA chart-type mapping software usually is designed for specific areas of coverage. Some of this mapping might have the Gulf Of Mexico divided into only one zone area, where others divide the Gulf into several different zones.

Many topographical mapping software packages are sold by states or in some cases by zones of the U.S., such as Southeast that covers Louisiana, Arkansas, Mississippi, Alabama, Florida and Georgia. I noted that one manufacturer offers these topo-type mapping in a scale of 1:24000. This is excellent detail for maps.

Many manufacturers also offer some type of Ortho aerial photo maps. However, you should note that photo images require a lot of data space. This means that you might run off the aerial map before reaching your actual destination.

Some manufacturers offer the aerial maps as a yearly subscription, which allows you to download the images to your computer. The selected areas are transferred form the computer memory to a spare memory card.

The largest consumer GPS manufacturers that have a line of fixed, mounted units are Garmin (, Lowrance (, Raymarine ( and Humminbird (

Find your unit and ascertain what mapping is available. If you see some mapping that would suit your needs, snoop it out and visit a stocking dealer to actually view your unit with the mapping software you want. Many dealers are listed in the Louisiana Sportsman Magazine.

When you find the mapping software, go to a location that you are familiar with and check that location on the screen. Zoom in on the location and see if the mapping software meets your needs.

Some of the software is pre-installed on a memory card, while some are only available for computer storage. From the computer, the user selects the area of coverage and user installs the data on a spare memory card.

Do your investigation and your homework. Doing so will save you a lot of money, and give you the type of unit and mapping you need for your type of navigation.

Should you have any questions, please submit your concern in the posting section under the Ask Captain Paul GPS section on the, and I will be happy to respond to your questions.

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About Captain Paul Titus 192 Articles
Capt. Paul Titus has been responding to G.P.S questions on since 2000. He has been fishing and hunting in Louisiana since 1957. Titus holds a USCG license and conducts instruction courses in the use of GPS for private individuals and government agencies.

1 Comment

  1. Capt. Paul,
    I just purchased a second boat that has a Humminbird G2 Chirp GPS unit. My primary boat has a Simrad GPS. The Humminbird unit only has a base map, so I need to purchase charts/map, and am considering the Navionics+ map. I would also like to update/upgrade my Simrad unit with the same map, if possible. I fish south Louisiana and Toledo Bend. I’m wondering if the Navionics+ is a good solution or if you might recommend something else.
    Your thoughts and comments would be much appreciated.

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