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Custom marine maps for 421S

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  • Custom marine maps for 421S


    I am trying to create a custom map from a hi resolution satellite image that i have for an area surrounding a small tropical island. I want to be able to see the small patch reefs on the Garmin 421s and also load a map that i have overlaid swept depth tracks tracks on top of the image in a GIS. I have tried a few forums and they say the unit should read a .img file and also a MAP file. I have create these and everytime i try to load these the unit says the map format is not supported?? Has anyone every created marine maps from satellite imagery and has anyone been able to load vector files (coastline shapefiles) onto the same unit??

    Any help will be very much appreciated.


  • #2
    I don't know what a MAP file is. The term ".img file" is ambiguous unfortunately. The .img extension is used for disk images and also for a type of raster images. But these are not the kind of .img files you need. Garmin's .img files are a proprietary format for vector based maps. They are not raster images (like satellite photos). The only tools you can use to create .img files have been reverse engineered by third parties because Garmin has never opened up the format.

    Have a look at Mapwel if you want to create .img files, it is pretty user friendly and should work well for a small map:

    If you want to use raster imagery however, I am not familiar with your device and don't know what formats it might use. This forum is intended for discussion of .kmz based maps for Garmin handheld devices. I sort of doubt that Garmin's marine units can use that kind of map. Here's an example of the "custom maps" that are the topic of this forum:



    • #3
      Originally posted by COLLINSP View Post
      I am trying to create a custom map from a hi resolution satellite image
      That kind of map you probably can create with Garmin software:

      If you prefer more available tools, than you could for example manually vectorize satellite image with GPSMapEdit and then compile into format acceptable by marine GPS using cgpsmapper.
      Dakota 20, 60CSx, nuvi 200, 1440t, 2340t, 3460t, 3540T, PL Topo, OSM, CN EU


      • #4
        The 421s is incapable of using KMZ files containing raster imagery as described here.