This might have been answered before - I have exported my bathy/elevation data to a global mapper grid. Then I zoom out the non surveyed areas become red (zero elevation or possibly maximum elevation which is close to zero). These areas don't have any elevations associated with them and GM doesn't give elevations for these areas. The red area does cover some other layers. When zoomed in the red areas dissappear. Is there a way to prevent this from happening? Is there another grid format that will provent this from happening?