.img files are intended for direct placement into the /Garmin folder on a GPS device's micro SD card.
According to community feedback on similar topographical downloads: TOPO1a.7z
“I found that North America and Europe probably take about 4-5 hours to download over wifi. It's significantly faster to download the maps onto the watch using Garmin Express on a PC.” Reddit · 4 years ago TOPO1a.7z
: The .7z extension indicates a high-ratio compressed archive created with 7-Zip . You must extract this file to access the map data within. TOPO1a.7z
: Use Garmin MapInstall to select and send the map to your connected device.
: Use a tool like 7-Zip or The Unarchiver to decompress the .7z file.