FAQ: Locations

Q: How are locations specified?
A: Locations may be ICAO, IATA, or FAA location codes or latitude and longitude.
Q: How do I enter a location by latitude and longitude?
A: The site will accept a variety of formats. Degrees alone may be specified or degrees and minutes, or even degrees, minutes, and seconds. The last value may also have a decimal and a fractional portion. Directions must be specified; latitude and longitude may be specified in either order. For example, the following are all valid ways to specify the location of San Francisco International Airport:
37.618817 N 122.375427 W 3737'07.74"N 12222'31.54"W 37d37'07.74"N 122d22'31.54"W 37d37m07.74sN 122d22m31.54sW 37 37 07.74N 122 22 31.54W 37 37N 122 23W N37 37 W122 23 W122 23 N37 37
Q: Can locations be specified by city or airport name?
A: If you use a city or airport name instead of a code you will be taken to the location database search. You can select the code you wish to use from the results, or change the spelling and search again.
Q: How can I find an airport's code?
A: You can find an airport's code using the site's search feature.
Q: Why do some airports have such goofy codes?
A: This is nicely answered in an excellent article by Dave English, Airport ABCs: An Explanation of Airport Identifier Codes, published in the December 1994 issue of the Journal of the Air Line Pilots Association, Air Line Pilot.
Q: What are the differences between the ICAO, IATA, and FAA location codes?
A: ICAO location indicators consist of four letters and are assigned by the International Civil Aviation Organization and published in ICAO Document 7910. They are assigned to aviation and certain other facilities worldwide.

IATA codes contain three letters and are assigned by the International Air Transport Association to airports and other transport-related facilities around the world.

FAA codes are assigned by the Federal Aviation Administration to airports within the United States of America, including its possessions and territories. FAA codes for airports with scheduled airline operations consist of three letters. Other FAA airport codes consist of three or four alphanumeric characters.

For US airports which have an IATA code, the IATA code is usually (but not always) the same as the FAA code. However, a US airport which does not have an IATA code may have a three letter FAA code which is the same as the IATA code for a non-US airport. One such airport is CBG. See What happens if the same code appears in several sources? for more information.

Q: What happens if the same code appears in several sources?
A: The same code can somtimes have different meanings according to different authorities. If IATA and FAA use the same code to refer to different locations, the Great Circle Mapper uses the IATA meaning of the code
Q: What if I want the FAA meaning of a code instead of the IATA meaning?
A: You can append .FAA to a code to use the FAA definition of that code if it differs from the IATA definition. For example, CBG (and CBG.IATA) refer to Cambridge, England. Use CBG.FAA if you want Cambridge, Minnesota.
Q: Why are IATA codes preferred over ICAO codes in many parts of the site?
A: The Great Circle Mapper has a very diverse user community. Some are pilots, and most or all of them prefer ICAO codes but understand IATA codes. Others are non-pilots, frequent-fliers and others who know IATA codes but often are unfamiliar with ICAO codes. A preference for IATA codes results in less overall confusion, even though it is inconvenient for some users.
Q: What point is the location of an airport?
A: A single latitude-longitude pair is a point, or a circle a few tens of meters in diameter if expressed to an arc-second of precision. Airports are a lot bigger than that, so what point is chosen to represent an airport's location?

The most common choice is the Airport Reference Point (ARP), which is the average of the latitude-longitude of each runway's center. For an airport with one runway, that's the middle of the runway, but with multiple runways it can be in seemingly odd places: for many years the ARP for Chicago's O'Hare (KORD/ORD) was in the parking structure.

Other choices are plausible and not uncommon. Sometimes different sources use different points to define an airport's locations, which leads to ambiguity as to where an airport is actually located. For example, when the Great Circle Mapper switched from using DAFIF data to AIP Algeria for DAOR/CBH the airport "moved" about 1.7 km. DAFIF used the ARP; AIP Algeria uses the apron right in front of the middle of the terminal.

Q: What does Part 139 certification for an airport mean?
A: Part 139 refers to 14 CFR Part 139 which requires the FAA to issue an airport operating certificate to US airports which serve scheduled air carrier operations with 10 or more seats or unscheduled (charter, not diversions) operations with 30 or more seats. There are four classes of airports which can be summarized as follows:

Class Scheduled Large
(30+ seats)
Scheduled Small
(10-30 seats)
Unscheduled Large
(30+ seats)
 Class I okokok
 Class II -okok
 Class III -ok-
 Class IV --ok
Q: What does "customs landing rights" mean?
A: The United States has several types of "international" airports, defined by Title 19 Part 122 of the Code of Federal Regulations. Specific internationl airports of entry are listed in 122.13. Landing rights airports can also provide customs and immigration services for international arrivals but require permission to land and are subject to other conditions as detailed in 122.14.

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