When looking at Dem4km.bgl with Tmfviewer it says it is LOD3.

But when you choose Lodgrid 3 you get squares of something like 500km.

You have to descend to lod grid 11 or more to get 4km squares.

What is the problem? Thank you

The toggling of the grid has nothing to do with displaying the data. It's the Level of Detail that will display properly. If the file loads at level 0 you see big, ugly blocks.