Sorry, but I don't understand what the Lock ICON does after reading the manual and playing a bit.
Could you elaborate about what is meand to "lock layer and allow to change zoom only in one layer"? How do you display multiple layers? I can switch between maps, but they do not appear to be layered.
When you enable lock on map, you can then zoom only in one zoom layer (the one on which you pressed lock button). Map will then be rescaled with every zoom in/ zoom out press. Just press lock and try to zoom in/ zoom out and you'll see what it do :)
Thanks for the explaination. I now understand what it does. The confusion was caused by the term "Layer". I was thinking of a layer in terms of a separate map layer as in Google Maps where you can enable and disable the map view layer on top of the sattelite view, or where you can add and remove a "My Tracks" layer on top of a map.
Here is an alternate way to describe the function of the lock button: "The lock button prevents the zoom function from loading new maps as you zoom in/out. Instead of loading new maps, the zoom function will simply enlarge or shrink the existing map. This may be useful if you have offline maps, do not have a particular zoom level and still wish to zoom in."