Thread: Dealing with odd-shaped maps (QCT to JNX conversion)

I'm trying to convert my Ordnance Survey Memory Map 1:25000 series maps in QCT format into JNX files for my Montana. Like this:

Load QCT file into Ozimaptrans, save as .MAP and .TIFF
Load .MAP into Global Mapper and export as JNX
Edit JNX (with a hex editor or jnxCustomizer) to set draw order and zoom level

The JNX maps thus made work fine when loaded onto my Montana (with the custom firmware). I have the Garmin 1:50000 maps and when I zoom in to 120m scale, the display switches to the 1:25000 JNX. Great!

But...

Many (most?) of the 1:25000 maps are oddly shaped, not rectangular. Ozimaptrans seems to write out a larger rectangular file that fits the whole oddly-shaped map within it, with any unmapped areas as blank white. From then on, everything sees these white areas as being part of the actual map.

So, if I move to the edge of the 1:25000 JNX map on the Montana, where there is one of these white areas, white is all I see on the screen. If I have two adjacent 1:25000 JNX files then the larger rectangles will overlap if their adjacent edges have a white area. Then, if the map currently on the Montana's screen has a white portion on the edge and the other (overlapping) JNX file has the actual map, then I still see the white until I am off the first map's file completely and into the second.

Have I explained that well enough?

Does anyone know how to get around this issue? Another work flow that I could follow to achieve the conversion (with the tools I have)?

The only thing I can come up with so far, and have tried successfully, is to simply save a cropped map either in Ozimaptrans or Global Mapper with the cropped rectangle within the bounds of the mapped region. I merged three maps in Memory Map to get the coverage I needed, loaded this into Ozimaptrans, then into Global Mapper, cropped in GM to the required rectangle and saved as JNX. That worked.

That will be a real pain in the bottom to do for the whole UK though, which it was my intention to have available. It takes long enough just converting each file without faffing about making perfectly adjacent rectangles out of them all.

Rick.