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Credits

The Great Circle Mapper, including all software, data, and the compilation and presentation of the data is Copyright © 1996-2025 Karl L. Swartz. All rights reserved.

The Great Circle Mapperƒ‡ name is a registered trademark.

The Great Circle Mapper logo is a trademark of the Great Circle Mapper.

Additional credits, copyrights, and licenses apply as detailed below.

Software

Great Circle Mapper software incorporates several third-party software libraries:

• Portions of this software are copyright © 2009 The FreeType Project and are used under license.
• GIF image processing is loosely derived from parts of Netpbm (license and copyright terms).
• Geomagnetic information is implemented using GeographicLib (license) and World Magnetic Model (WMM) data (see below).
• AES encryption is implemented using software from Brian Gladman (license and copyright terms).
• SHA-1 signatures are implemented using software derived from RFC 3174 (license and copyright terms).

Geodesic calculations use custom software based on formulae developed by Thaddeus Vincenty, with modifications by Charles Karney based on work by Friedrich Bessel to improve performance and accuracy. (See How does the Great Circle Mapper calculate distances and paths? in the FAQ for additional information and references.)

Primary development of the Great Circle Mapper is done using an Apple Macintosh and servers running FreeBSD. The site is hosted using the Apache HTTP Server running on FreeBSD.

Made on a Mac

Mac and the Mac logo are trademarks of Apple Computer, Inc., registered in the U.S. and other countries. The Made on a Mac Badge is a trademark of Apple Computer, Inc., used with permission.

Map Data

The Great Circle Mapper uses pre-rendered maps, stored in a custom, high-performance image format. These maps are built offline from multiple sources:

• Plain maps and most political boundaries are derived from GMT (Generic Mapping Tools). No GMT code is used in the online portion of the web site.
  • The revised border between Saudi Arabia and Qatar is derived from Agreement on the Delimitation of the Offshore and Land Boundaries between the Kingdom of Saudi Arabia and Qatar.
  • The revised border between Saudi Arabia and the United Arab Emirates (UAE) is derived from the Agreement on the delimination of boundaries (UN Treaty No. 30250).
  • The updated border between Eritrea and Ethiopia is approximated using data from the Decision Regarding Delimitation of the Border between The State of Eritrea and The Federal Democratic Republic of Ethiopia from the Eritrea - Ethiopia Boundary Commission (EEBC).
  • The border between Sudan and South Sudan is based on U.S. Department of State data via WikiProject South Sudan, with additional information from an Ogle Earth article.
• Blue Marble and Night maps are based on Blue Marble: Next Generation (and Blue Marble) imagery from NASA's Earth Observatory.
• Lunar maps use public-domain imagery, based on data from the Clementine mission processed into images by the United States Naval Research Laboratory. Some Clementine imagery was obtained via Calvin J. Hamilton's Views of the Solar System.
• Mars maps are based on maps created by NASA's Jet Propulsion Laboratory (JPL/Caltech) and the U.S. Geological Survey (USGS) for the Solar System Simulator.
• Pluto maps are based on imagery from the New Horizons mission, processed and made public by NASA, The Johns Hopkins University Applied Physics Laboratory, and the Southwest Research Institute.
• Facebook connections maps are from the Visualizing Friendships work done by Paul Butler and are copyright Facebook.

Airport Data

The Great Circle Mapper's location database includes information about landing facilities (including airports) and other types of locations compiled from many sources including those listed below. Specific source credits are noted on the information page for the airport or location.

• The primary source for most landing facilities in the United States is the FAA's National Flight Data Center (NFDC), with additional data provided by Paulo Santos (AirNav).
• The primary source for most landing facilities in Iceland is the Icelandic Civil Aviation Administration, provided by Sigurbj?rn Ragnarsson (Flugnet) with translation help where needed.
• The primary source for landing facilities in many other countries is the Aeronautical Information Publication (AIP) of the civil aviation adminstration which regulates the facility.
• The primary source for some landing facilities is the facility itself, often based on AIP data which is not otherwise readily available.
• The primary or secondary source for numerous landing facilities is the last public release (cycle 0610, effective 28 September 2006 to 25 October 2006) of DAFIF^®, a product of the National Geospatial-Intelligence Agency. The Great Circle Mapper has not been endorsed nor otherwise approved by the National Geospatial-Intelligence Agency, the former National Imagery and Mapping Agency, or the United States Department of Defense (10 U.S.C. ƒ@ 425).
• Some airport information has been derived from the Bones Aviation Page with the permission of John Woodside.
• On-site surveys by the Great Circle Mapper are used for a few facilities where official sources are unavailable.
• Photogrammetry by the Great Circle Mapper is used for some airports where official sources are unavailable, low precision, or incorrect. The processes used have been verified using airports for which accurate, reliable information is available.
• Additional airport information has been contributed by Thomas Jäger, Iikka Meriläinen, Yann Gascard (Virtual Pilots Association), Nils Rennenberg, and many others.

Other Data

Magnetic variation information is derived from the World Magnetic Model (WMM), a product of the U.S. National Geospatial-Intelligence Agency (NGA) and the U.K. Defence Geographic Centre (DGC) which was developed jointly by the U.S. National Geophysical Data Center (NGDC) and the British Geological Survey (BGS). This data is in the public-domain and is not subject to copyright protection.

Time zone definitions including daylight saving time (DST) transitions use the public-domain Timz Zone Database (aka tz or zoneinfo). The time zone for a given location is derived from official airport data or other sources and may not be correct.

Flags

Flags used on the airport information pages are from one or more of the following vexillological sources:

• Mooney's MiniFlags, with the kind permission of Edward Mooney, Jr.
• The CIA's Flags of the World (part of the World Factbook).
• Roberto Breschi's Bandiere, used with permission.
• Flags from Australia at OzOutback, used with permission.
• flags-and-anthems.com.
• Various government and public-domain sources.