If you want to stick with arrays you could use offset x/y variables to pick the data directly from the big array.
ofcause you would have to make sure that the offset variables doesn't go past you max level size minus the number of data you pull. In the above example the limit would be 10000-100. That way you don't have to read the data into another array first.
dim level(10000,10000) for y = 0 to 99 for x = 0 to 99 leveldata = level(x+offsetX,y+offsetY) ; do whatever you need with the data. next next
ofcause you would have to make sure that the offset variables doesn't go past you max level size minus the number of data you pull. In the above example the limit would be 10000-100. That way you don't have to read the data into another array first.