There is a limit the increment of this function that it may take a long time to generate the label.

The function use global latitude and longitude to setup: ;n_lats = 1 + fix((latmax-lat0)/float(latdelta)) chang n_lats = 1 + long((latmax-lat0)/float(latdelta))

Later on, when the script draw all the label, the loop is like this:

FOR i=0,n_lats-1 DO BEGIN So, a small increment will lead to long run time.