In this task, you will be given a passage to read. A fill in the blank question will be given to you.  Your answer should fit the blank appropriately.
Q: The factors used in determining how an individual aerodrome is categorised by the GASAR study are based broadly on size and facilities . The six types of aerodrome are described , in size order , as : regional airports ( e.g. East Midlands ) ; major GA airports ( e.g. Oxford ) ; developed GA airfields ( e.g. Andrewsfield ) ; basic GA airfields ( e.g. Rufforth ) ; developed airstrips ( e.g. Tilstock ) ; and basic airstrips ( e.g. Chilbolton in Hampshire ) . The actual criteria used to categorise aerodromes were complex , using 28 different parameters , backed up with a peer review by experienced GA pilots .Airports generally have long , fully lit , hard @-@ surfaced runways , full air traffic control , and navigation and landing aids . They are usually located on urban fringes , support commercial and business operations , and often exclude certain types of light aircraft . At the more rurally located airfields , the lighter end of aviation , such as microlight and gliding activities , becomes increasingly prevalent , and there are few or no commercial operations other than flying schools . At this level runways are generally shorter , and grass surfaces are increasingly common . Navigation aids are increasingly scarce , being more basic where they are available , and informal ground to air radio communication replaces air traffic control . The smallest airfields are too small to feature on general purpose Ordnance Survey ( OS ) maps , and lack basic facilities such as fuel and maintenance . The majority of airstrips are basically single short grass runways with no supporting facilities , although the presence of a hangar is not uncommon at the larger examples . They do not feature on OS maps , and are owned by private clubs or , more commonly , individuals . fill in the blank  :The factors used in determining how an individual aerodrome is categorised by the GASAR study are __________________ broadly on size and facilities . 
A: 
 based 