I know that. Positive value is not the problem. The problem is the negative value in xsize itself when I tried to make it face the opposite side. I just posted an attachment so you can see what I mean. I get crash every time I set it negative. What build can I use that works well with negative values for xsize?
EDIT: Never mind. I just figured/realized that there's no need for nega value for xsize. I just adjusted amin higher and amax lower, and that works well for facing in opposite direction.
basemap 3495 579 46 3 52 0