What is IMDF? The indoor map format, explained

IMDF at a glance

Where IMDF came from

Apple developed IMDF so that venue owners could describe the inside of a building in one consistent way, then show those maps in apps and websites through its MapKit framework. It was submitted to the OGC in July 2020 and approved as a Community Standard in February 2021.

A Community Standard is a specification written outside the OGC that the OGC adopts as it stands. The OGC document says so directly: the originating party may keep updating its own work, while the OGC text stays fixed. In practice that means two copies, and when a tool says it supports IMDF it is worth asking which one.

What is inside an IMDF archive

An IMDF dataset is a single ZIP file. Inside it, each feature type has its own GeoJSON file, and a small manifest says which version of IMDF the archive follows and which language its names default to.

wayvale-general.zip IMDF 1.0.0

File	Geometry	What it holds
manifest.json Required	n/a	IMDF version, creation time, default language, extensions used
address.geojson Required	none	Postal addresses the other features point to
venue.geojson Required	Polygon	The one venue: the whole site, its name and hours
building.geojson	none	Each building; its outline lives in the footprint
footprint.geojson	Polygon	Building outlines: ground, aerial or subterranean
level.geojson	Polygon	Each floor, with an ordinal for stacking order
unit.geojson	Polygon	Rooms, walkways, lifts, stairs, restrooms
opening.geojson	LineString	Doors and entrances on unit edges
fixture.geojson	Polygon	Fixed objects inside units, such as counters
section.geojson	Polygon	Areas within a level, such as a food court
geofence.geojson	Polygon	Virtual boundaries that can cross units and levels
kiosk.geojson	Polygon	Physical directory and map structures
amenity.geojson	Point	Services such as first aid, information, ATMs
anchor.geojson	Point	A point inside a unit that occupants hang from
occupant.geojson	none	Tenants and businesses, with hours and contacts
detail.geojson	LineString	Extra linework drawn on a level
relationship.geojson	varies	Traversals: lifts, ramps, escalators, one-way doors

How features point at each other

• unit.level_id → points to level
• opening.level_id → points to level
• level.building_ids → points to building
• footprint.building_ids → points to building
• amenity.unit_ids → points to unit
• occupant.anchor_id → points to anchor → unit

Three of the files are required: the manifest, the addresses and the venue. Everything else is optional, which is why two IMDF exports of the same building can look very different. One might stop at levels and units; another might add every door, counter and shop tenant.

How a floor plan maps onto IMDF features

The easiest way to read IMDF is to lay it over a floor you know. Here is the ground floor of a fictional hospital, with each part labelled by the feature type and category it becomes.

The level is the outline of the whole floor. Units fill it: rooms, the corridor, the restrooms, the lift lobby, each with a category from IMDF’s fixed list. Openings are lines, not shapes, and they sit on the edge between two units, which is how a reader knows that the pharmacy opens onto the corridor. Occupants such as a pharmacy operator or a café brand have no geometry of their own; they hang from an anchor point inside a unit.

What one feature looks like

This is a single unit from unit.geojson, the pharmacy in the drawing above. The coordinates are illustrative.

{
  "id": "8c5e6a72-3f1d-4b8e-9a47-2d61c0f3b915",
  "type": "Feature",
  "feature_type": "unit",
  "geometry": {
    "type": "Polygon",
    "coordinates": [[
      [77.2310421, 28.6395118],
      [77.2311733, 28.6395118],
      [77.2311733, 28.6393956],
      [77.2310421, 28.6393956],
      [77.2310421, 28.6395118]
    ]]
  },
  "properties": {
    "category": "room",
    "restriction": null,
    "accessibility": null,
    "name": { "en": "Pharmacy", "ar": "الصيدلية" },
    "alt_name": null,
    "level_id": "1f0b9d34-7c2a-4e65-b8d1-5a93e2c47f08",
    "display_point": {
      "type": "Point",
      "coordinates": [77.2311077, 28.6394537]
    }
  }
}

Three things to notice. The feature_type member says what the feature is, on top of ordinary GeoJSON. The level_id points to a level by its UUID, which is how features are tied together across files. And the name is a set of labels by language, so a bilingual directory does not need two maps.

What IMDF is used for

If you are writing a specification, require that the venue can be exported in an open format such as IMDF at any time, without a fee or a support ticket. Our vendor-neutral tender specification has a clause for it.

What IMDF does not cover

IMDF describes the building. It does not describe how people move through it, or what is happening in it today.

So an IMDF file is a good starting point for a wayfinding map, and a good way to get a map out again. It is not a finished wayfinding map on its own: someone still has to build and check the route network.

How DigiMaps works with IMDF

If your plans are in CAD rather than IMDF, start with the floor plan import formats instead. DXF is read directly, and our DWG to interactive map guide walks through the whole conversion.

Checking an IMDF file before you hand it over

Whether you are receiving IMDF from a contractor or sending it to Apple, a few checks catch most problems.

1. Open the ZIP and confirm that manifest.json, address.geojson and venue.geojson are there.
2. Check that the manifest version is 1.0.0 and that its language tag matches the language most of your names are in.
3. List the levels and their ordinals. They should stack in the order a visitor would ride the lift, with basements below the ground floor.
4. Spot-check that units sit inside their level, and that neighbouring units do not overlap or leave slivers between them.
5. Pick five rooms visitors need to reach and confirm that each has an opening on its edge.
6. If the archive was merged from several sources, look for repeated IDs. Every ID must be a unique UUID that is never reused.
7. Read the names in every language you will publish. Arabic names should not fall back to Latin room codes from the drawing.
8. If the file is going to Apple, load it into the IMDF Sandbox and work through the errors and warnings it reports.

Sources

Checked 24 October 2026.

• OGC, Indoor Mapping Data Format 1.0.0, document 20-094 (status, dates, feature types, archive and manifest rules)
• Apple, Indoor Mapping Data Format (Apple’s current copy of the specification)
• Apple, Indoor Maps Program (MapKit, the IMDF Sandbox and the Indoor Survey app)
• IETF, RFC 7946: The GeoJSON Format (coordinates on WGS 84)