GPS Map: AT5 File Extension

By G.D. Palmer

The .at5 file extension is associated with mapping and global positioning systems programs produced by Lowrance, a software and electronics manufacturer for anglers, recreational boaters and other sports enthusiasts. AT5 files work primarily with Lowrance MapCreate and NauticPath programs, but can be opened using other applications from the same manufacturer. These files are meant to work with the company's proprietary GPS and fish finder systems, and are not compatible with ordinary computers.


AT5 files contain mapping and GPS data, which Lowrance products interpret to show a map on screen. Depending on the kind of AT5 file, it can contain aviation information, coastal navigational charts or inland road, shoreline and waterway data. Lowrance devices allow users to customize the data in these files, including the information they need for boating or other outdoor sports.


Files for Lowrance devices provide a range of helpful features, including detailed maps of waterways, plus depth contours and elevations. Many AT5 files offer shoreline detail not found in other map types, which allows anglers and other sports enthusiasts to find their favorite locations easily. You can add your own points of interest, or POIs, to the file, and the device automatically pops up information boxes to tell you more about these locations. AT5 files work with databases on Lowrance devices to provide hotel, transportation, restaurant and emergency service information.


Lowrance GPS and mapping devices use a proprietary data format that doesn't work with any other mapping program or device. AT5 files are made exclusively for devices from this company, but should work across the Lowrance line, as long as you load them into the appropriate kind of device. For instance, you can open marine AT5 files using any compatible Lowrance marine mapping software, but these devices can't interpret the company's aviation AT5 files correctly.


Because Lowrance uses a special standard, sports enthusiasts transitioning to another brand of fish finder or GPS mapping system can't use their old maps. As of December 2011, no conversion utility between brands exists, making Lowrance a poor choice for people who regularly change device brands. Lowrance devices can import data from some other brands of GPS, however.