openAIP for spotters: use airfields, airspaces and frequencies for free

Where is the nearest glider field, which frequency does the tower use, and which compass direction does runway 26R really point? For questions like these you don’t have to page through official handbooks. openAIP bundles airfields, airspaces, frequencies and much more in a free worldwide database that you can search in your browser, download or query through an interface. This guide shows you what’s in it, how to put the data to good use as a spotter and when you should go to the official source instead.

openAIP in one sentence

openAIP is a web-based, community-maintained platform for aeronautical information: volunteers from all over the world compile the data, anyone can use it for free, and developers can integrate it into their own applications through interfaces. The website names Garrecht Avionik GmbH as the operator. The name alludes to the AIP, the Aeronautical Information Publication – the official aviation handbook that every country publishes for its airspace.

The difference from the official AIP is crucial: there, authorities and air navigation service providers publish binding information, country by country, each in its own layout. openAIP merges this kind of information into a uniform, machine-readable format. That makes the data attractive for hobby projects, map services and flight navigation apps – and for spotters who need a quick overview.

What’s in the database

The website’s navigation shows the data categories at a glance. Each has its own searchable list and appears on the interactive map:

Category	What’s in it	Use for spotters
Airports	Airfields of all kinds with runways, frequencies, elevation, operating hours	Find fields, look up runways and radio
Airspaces	Airspaces with class, type, lower and upper limit	Understand where and why traffic flies
Reporting Points	VFR reporting points	See where small aircraft enter a control zone
Navaids	Radio navigation aids such as VOR or NDB	Get a rough idea of approach routes
Obstacles	Aviation obstacles	Orientation in the terrain around the field
Special Rules Areas	Areas with special rules	Recognize special zones
Hang Gliding Sites	Launch and landing sites for hang gliders and paragliders	Subjects beyond powered flight
Hotspots	Thermal sources, rated by reliability	Mostly for glider and paraglider pilots
RC Airfields	Model airfields	Side info, but handy for drone users

Airfields: more than the big hubs

What makes this exciting for spotters is the range of airfield types. openAIP distinguishes international airports, civil airfields, military airfields, glider sites, ultralight fields, civil and military heliports, seaplane bases, simple airstrips, mountain altiports and closed airfields, among others. Each entry can include the ICAO and IATA code, field elevation, traffic type (VFR or IFR) and notes such as prior permission required (PPR), private field, parachute operations or winch launch only.

Small fields in particular are barely visible on many flight tracker maps. If you’re interested in light aircraft, gliders or vintage planes, openAIP is a good starting point – there’s more in the guide on finding small airfields, glider sites and ultralight fields on maps. What you’ll typically encounter there is covered in recognizing light aircraft.

Airspaces: the invisible architecture

In openAIP, airspaces carry their ICAO class from A to G as well as a type. The list of types is long: control zones (CTR), terminal control areas (TMA), transponder and radio mandatory zones (TMZ and RMZ), restricted, danger and prohibited areas, temporarily reserved areas, glider sectors and more. On top of that come upper and lower limits, activation times, notes on activation by NOTAM and, where needed, frequencies or transponder codes.

For you as a spotter, this explains why traffic flies low in some places and not in others. The basics are in airspace classes A to G and in the practical guide recognizing airspaces on maps. Current activations and closures are published in NOTAMs – how to read and understand NOTAMs shows you how to read them.

Three spotter uses that are really worth it

1. Looking up frequencies

For each airfield entry, openAIP can keep a list of frequencies, each with the type of service. The types range from tower, ground, approach, departure and delivery through apron and ATIS to information, AFIS, Unicom or glider frequencies. Values are written with three decimal places, as is common in today’s 8.33 kHz channel spacing – the article on 8.33 kHz channel spacing explains why.

For listening in at the fence, that’s a quick cheat sheet. What the individual services mean and which frequency is active in which phase of flight is covered in understanding ATC frequencies. Before you switch on a scanner, please read listening to aircraft radio: the legal situation – receiving, recording and passing on transmissions are not regulated the same way everywhere.

2. Runway heading for light planning

For every runway, openAIP stores the designation, the true heading in degrees, length, width, surface and approach aids. At Munich Airport, for example, you’ll find for runway 08L/26R not only the dimensions of 4,000 by 60 meters but also the true direction of both ends – roughly 80 and 260 degrees.

The advantage over the runway number: the number is rounded to ten degrees and refers to magnetic north. The value in openAIP gives you the geographic direction directly. Combined with the sun’s azimuth, you can tell when the sun is behind you at a spot – the full calculation logic is explained in planning sun position. Which end of the runway is used on a given day is decided by the wind; there’s more in understanding the runway direction in use at an airport.

3. Discovering new fields nearby

Zoom the map into your region and you’ll quickly see how many airfields there are besides the big airport: glider sites, ultralight fields, special-purpose airfields. The detail view tells you whether powered flying takes place there at all, whether the field requires PPR and whether it is limited to winch launches. These are valuable hints especially for airfield festivals and small fly-ins; our overview of airfield festivals in Germany collects dates.

How to use openAIP step by step

If you can’t yet match ICAO codes with confidence, IATA and ICAO codes explained will help. For the location of fences, paths and parking lots at a field, OpenStreetMap for spotters complements the aviation data nicely – openAIP shows you the runway, OpenStreetMap the dirt track to get there.

Exports and API for tinkerers

If you want more than the map, the “Data Exports” page offers ready-made files, sorted by country and data type (airfields, airspaces, navaids, reporting points, obstacles). The available formats:

Format	Typical use
GeoJSON and line-delimited GeoJSON	your own web maps, GIS programs such as QGIS
JSON	your own analyses and scripts
SeeYou CUP and CUPX	gliding software and devices
OpenAIR (versions 1 and 2)	airspace files for flight computers in gliding and paragliding
openAIP v1 (XML)	older applications that expect the former format

For developers there is a Core API for the datasets themselves and a Tiles API that delivers geometries as Mapbox vector tiles. You generate the key in your own profile under “API Clients” and pass it as the HTTP header x-openaip-api-key or as a query parameter. openAIP points out rate limits and recommends caching responses. The service also asks that your own applications include a link to openaip.net as the data source.

On GitHub the project also publishes small tools, such as a parser that converts OpenAIR airspace files to JSON or GeoJSON and a converter for the simplified aviation data model YAIXM. If you already play with ADS-B data, you can use them to combine position data and airspaces on a shared map – tracking flights on your PC with tar1090 and Virtual Radar offers ideas.

License: what’s allowed

The openAIP data is released under Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). In practice, that means:

For a spotter blog, a private map or a club project, this is usually unproblematic as long as you credit openAIP as the source. As soon as money is involved, read the license terms carefully or ask the operator.

Limits: when openAIP isn’t enough

openAIP runs on volunteers. That’s its strength – and its limit. There are a few points you should know:

• Not an official source. The binding publications are the AIPs of the respective air navigation service provider, in Germany those of DFS. They are mandatory for actual flying; openAIP is a supplement at best.
• Varying depth of data. How completely a country or an airfield is recorded depends on how active the community is there. Frequency lists or operating hours can be incomplete.
• Time lag. Changes in the official AIP don’t automatically show up right away. Temporary closures are published in NOTAMs anyway, not in a static database.
• No drone clearance. For drone flights in Germany, the official map is what counts – more in geozones and the dipul map and drones at airports.
• No live data. openAIP shows infrastructure, not aircraft. Flight tracker services tell you who is landing right now; the flight tracker app comparison gives an overview.

Contribute yourself

If you find a wrong entry, you can correct it: with a free account you submit change requests. openAIP publicly shows the most recently submitted requests under “Latest Change Requests” – a look there tells you how lively the upkeep is at the moment. For discussion, the project lists a discussion group, Slack, Mastodon and GitHub.

Spotters are especially well suited to this: you often stand at fields that few people visit and can see whether a grass runway is still in use or a field closed long ago. Stick to facts you can back up, and don’t copy anything from protected sources.

Conclusion

openAIP is an underrated tool for spotters. In a few clicks, the database delivers what you need for a good spotting day: frequencies for the radio, the true runway heading for light planning and an overview of small fields that don’t show up on any flight tracker. With exports and the API, it becomes raw material for your own maps and analyses. There’s just one thing openAIP must not be: your only source when it comes to anything binding. That’s what the official publications are for.