Equirectangular projection is a way of flattening a full sphere of view into a single rectangular image that is twice as wide as it is tall. It is the standard format for 360 photos, in the same way a world map flattens the globe. Viewers wrap the flat image back onto a sphere so you can look around in any direction.
How the Flat Image Maps to a Sphere
Horizontal position in the image represents the angle around you, covering 360 degrees from left to right. Vertical position represents the angle up or down, covering 180 degrees from the top to the bottom. Because every row has the same width, areas near the top and bottom are stretched sideways, which is why a ceiling or floor can look distorted in the flat version but normal inside a viewer.
- Left and right edges meet at the same point in the scene.
- The top edge is a single point straight up, stretched across the whole width.
- The bottom edge is the point straight down, often where the tripod appears.
How a 360 Photo Gets Captured
- A 360 camera uses two or more wide lenses, each covering part of the sphere.
- The camera or software joins the overlapping areas, a step called stitching.
- The result is saved as an equirectangular image, usually in a 2:1 ratio.
- Metadata tells platforms that the file is a 360 panorama, so they display it correctly.
Another method uses a regular camera on a panoramic head, taking many overlapping shots that are stitched later. This can give more detail but takes longer and needs careful alignment.
Where Problems Come From
- Stitching lines: visible seams appear when objects sit close to the camera.
- Parallax: the lenses see near objects from slightly different positions, so keep subjects at a comfortable distance.
- Tripod and stand: they show at the bottom, and can be hidden by editing or a small patch.
- Tilt: if the camera is not level, the horizon curves, though many viewers allow correcting it.
| Format | Typical use |
|---|---|
| Equirectangular | Storage and editing of 360 photos |
| Cube map | Games and some viewers |
| Little planet | Creative flat view from the same data |
FAQ
Why is the file always twice as wide as tall?
The width covers 360 degrees and the height covers 180 degrees, so the ratio is 2:1.
Can I edit an equirectangular image like a normal photo?
Yes for color and exposure. Be careful with cropping, because it breaks the sphere, and with edits near the top and bottom where stretching is strongest.
The Short Version
Equirectangular projection is the flat map of a sphere used for 360 photos. Keep a 2:1 ratio, avoid subjects too close to the lenses, and let a viewer do the wrapping.
