I've built a map that I use for my Lowrance HDS Carbon unit and it works well. I recently found an old topographical map of the lake area before it was flooded and wanted to create a map with this as the background. I made a clone of my original map, added the topo map as an image with the countour lines above this. It displays nicely in Reefmaster but I can see I will want to be able to turn these on and off at different times depending on the detail I need for the background image. Is there a way to set this up so the major and minor contour lines can be turned on/off on the Lowrance unit? Is this possible? If so, do I need to do anything special or just have the contours as a layer on top of the background? Where does one go in the Lowrance menu to turn these on/off? Thanks in advance!

You can turn the major and minor contour lines on/off using the major map categories (MAJ_CAT) if they are available as separate names. However to turn on/off, you always have to find the chartcategories on the unit first a few clicks).
To change the MAJ_CAT, export the lines from RM as shape and us a GIS application to adapt (in the major and minor lines shape rename "NAUTICAL" in the field MAJ_CAT into 2 different names).
For AT5 vector generation directly use the IMC (set "auto create xml" for use over raster).

There is also an other/better solution over the DVOR function, but this is much more complicate.

Thanks for the information...not as simple as I had hoped, but I'll play around with this and see if I can get it to work. Thanks again!