GmapTool 

Split your Garmin maps into mapsets, maps, and subfiles or merge multiple IMG files into a Garmin map. The tool includes the ability to install mapsets that work with other services such as BaseCamp, HomePort or Mapsource. It also adds information to the maps and keeps a log with all the operations it performs.

GMapTool is a free software program for splitting and merging maps in Garmin format. Its main purpose is to combine maps in img format and divide files in img format into mapset, maps, and subfiles of maps. Additionally, the application can install mapsets for use with programs such as Mapsource, BaseCamp, and HomePort. It also has the capacity to edit map features, for example, map type, priority, transparency, name, and creation date, and modify maps, transforming labels case, deleting national characters, and replacing TYP files. The Windows version of the program is available in multiple languages. Additionally, the command-line version gmt.exe can be utilized.