Equirectangular Panoramas Explained
An equirectangular panorama is a 360° photograph stored as a flat rectangle exactly twice as wide as it is tall. Longitude runs along the width, latitude along the height, so the top and bottom edges — the zenith and the nadir — are stretched across the full width of the image. It looks distorted in a photo viewer and correct in a 360° viewer, which wraps it back onto a sphere. Every consumer 360° camera exports this format, and it is what virtual tour software expects.
If you have opened a file straight off a 360° camera and found a wide, warped image with a smeared sky, nothing is wrong. That is the format working as designed.
Why the image looks stretched
The projection is the same idea as a world map. A globe cannot be laid flat without distortion, so cartographers pick which distortion to accept. Equirectangular picks the simplest rule available: horizontal position is longitude, vertical position is latitude, both spaced evenly.
The consequence is that a point at the pole — straight up, straight down — has to occupy the entire top or bottom edge of the rectangle. The ceiling light directly above the tripod becomes a smear across the whole width. On a sphere it is a point again.
The 2:1 ratio is not a style choice
360 degrees around, 180 degrees top to bottom. Twice as wide as tall, exactly. If your file is 16:9 or 3:1, it is not a full sphere, and a viewer will either refuse it or wrap it wrongly.
What a good file looks like
| Property | What to aim for | Why |
|---|---|---|
| Aspect ratio | Exactly 2:1 | Anything else is not a full sphere and will wrap wrong |
| Resolution | 5760 × 2880 or better | The visitor only ever sees a slice of it; a small file looks soft the moment they zoom |
| Format | JPEG | Universally supported and small enough to load over a phone connection |
| Horizon | Level, halfway down the frame | A tilted horizon in a 360° view is genuinely disorienting |
| Nadir | Patched | Otherwise the tripod and your shoes are in the floor of every room |
Resolution is the one people underestimate. A 6K panorama sounds enormous next to an ordinary photo, but the visitor is looking at maybe a tenth of it at any moment — roughly the detail of a 1.5 MP snapshot. That is why 4K panoramas look crisp in a thumbnail and mushy in the viewer.
Metadata, and when it matters
360° cameras write XMP tags that mark the file as a full sphere. Some viewers and most social platforms read them and refuse to show the photo as a panorama without them. A tour builder that goes by the 2:1 ratio does not care — but an editor that strips metadata on export can still break the file for everywhere else, so prefer editors that keep it.
Where equirectangular comes from
- One-shot 360° cameras — two fisheye lenses, stitched in the camera. The export is already equirectangular.
- A DSLR on a panoramic head — several overlapping frames, stitched on a computer. More work, more resolution, more control over exposure.
- Rendered scenes — 3D software can output a spherical camera directly, which is how furnished show-home tours of unbuilt properties are made.
Other projections you may run into
| Projection | Looks like | Used for |
|---|---|---|
| Equirectangular | One 2:1 rectangle, poles smeared | The standard for 360° photos and tours |
| Cubemap | Six square faces | Game engines and viewers that want cheap rendering |
| Fisheye | One or two circles | The raw frames before stitching |
| Little planet | A circular world seen from above | A stereographic view for social posts, not a tour source |
Little planet images come up a lot because they are eye-catching, and they are sometimes mistaken for the source file. They are a rendering of one, usually with the data outside the circle thrown away — not something a tour can be built from.
Using one in a tour
Upload the JPG, and it becomes a scene the visitor can stand in. The full process — shooting, naming, linking the doorways — is in how to make a virtual tour, and how the builder works shows what happens to the file after the upload.