Automating the production of GPS-compatible map tiles from georeferenced raster maps

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I have a set of TIFF maps that I want to load onto Garmin GPS 62s units. The maximum size for each tile on the GPS is 3Mb and less than 1 million pixels. I manually produced one tile, following this workflow:

1. Convert whole TIFF map to JPG using IrfanView
2. Manually crop the image to be less than 1 million pixels (i.e. 1024X1024) and compress to be less than 3Mb.
3. Add JPG to QGIS and georeference using the georeferencer tool.
4. Add same JPG image to Google Earth as an Image Overlay.
5. Use the Extent information from the georeferenced JPG in QGIS to fill out the extent boxes in Google Earth.
6. Save as KMZ file.
7. Add KMZ file to Garmin Basecamp.
8. Add KMZ to GPS unit with Basecamp.

This is obviously a slow and fiddly process which I am reluctant to repeat 100 times to produce all the tiles needed.

Is there a way to automate sections of this? Specifically I imagine the follow are possible, but don't know of any tools to do it:

• Automatically divide one georeferenced raster into multiple tiles of given dimensions, retaining geocoded information, in QGIS.
• Export multiple tiles into a KMZ file in QGIS

This would make the process a lot quicker. The closest tools I have found is the GarminCustomMaps plugin for QGIS, but this just takes a JPG image of your current map canvas - great for using with multiple vectors etc, but when zoomed out with large raster files, I just get a very pixelated image which is useless for reading on a GPS. Zooming in more to increase the resolution negates the point of it, as you'd have to repeat it multiple times.

Any suggestions of tools or methods would be appreciated!



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