An equirectangular image is a 360-degree photo unfolded into a rectangle. It's the format almost every virtual tour uses: the camera or drone captures everything around it, the software stitches it into a sphere and that sphere is stored "flattened," just like a world map.
If you've ever opened a 360 photo on your computer and seen it stretched and curved, you were looking at an equirectangular image. In this guide I explain how to read it, why it looks distorted, what resolution you need, how it's created with different equipment and what to check before publishing it in a 360 tour.
What is an equirectangular image?
It's a way to store a full sphere in a rectangle. Each point in the image corresponds to a viewing direction:
- From left to right it covers the 360° around the camera.
- From top to bottom it covers 180°: from the sky directly above to the ground directly below.
Since 360 is twice 180, the image is always twice as wide as it is tall. That's called a 2:1 ratio. A panorama of 6000 × 3000 or 8192 × 4096 pixels is equirectangular; one of 6000 × 2000 is not.
The name comes from how the degrees are distributed: each degree of rotation takes up the same width in the image and each degree of tilt takes up the same height. It's the same projection as world maps where every line of latitude and longitude forms an even grid.
How to read an equirectangular image
- The center is the front. It's where the camera or drone was pointing during capture.
- The middle line is the horizon. In a good panorama it's straight.
- The edges touch. What you see on the left edge continues on the right edge: both show what's behind the camera.
- The top row is a single point. The whole top part is the sky directly above (the zenith).
- The bottom row is also a single point. It's the ground directly below (the nadir). In a drone shot, that's where the drone itself would be if it isn't corrected.
Why does it look stretched?
Because a sphere can't be flattened without distortion. At the horizon, a full circle is very long; near the sky or the ground, the circle gets smaller and smaller until it becomes a point. But in the image every row is the same width, so whatever is at the top and bottom gets stretched.
This has two practical consequences:
- It's not a mistake. The tour viewer projects the image onto a sphere and the distortion disappears. Whoever goes through the tour never sees it.
- Touch-ups near the top and bottom are delicate. A logo pasted "flat" at the bottom of the image will look distorted in the tour. To cover the ground or add a logo, you work in a view that corrects for the sphere or with the patch tool in the tour software.
What resolution does it need?
The measure that matters is how many pixels you have for each degree of view: the image width divided by 360. When the user zooms in, that defines how sharp it looks.
| Width × height | Pixels per degree | What it's enough for |
|---|---|---|
| 4096 × 2048 | 11 | Preview or social media. Looks soft when zooming in. |
| 6000 × 3000 | 17 | Interior tours and general views. |
| 8192 × 4096 | 23 | Drone tours where the user zooms in to see lots or roads. |
| 12000 × 6000 or more | 33 or more | High detail. Needs a viewer that loads the image in parts. |
Two clarifications:
- More pixels don't fix a bad shot. If the original photos came out blurry or underexposed, enlarging the image only enlarges the problem.
- File size matters on phones. A very large panorama takes a while to load on mobile data, and some phones can't display a single huge image well. That's why professional viewers split the panorama into tiles and load only the part being viewed, with more detail as the user zooms in.
How an equirectangular image is created
There are four paths. They all end in the same place: many photos or views covering the full sphere, stitched into a single 2:1 file.
1. With a 360 camera
Consumer 360 cameras, such as Insta360 or Ricoh Theta, have two back-to-back fisheye lenses. Each lens captures a bit more than half the sphere, and the camera app stitches them and exports the equirectangular image.
- Advantage fast, one shot per point. Ideal for interiors, model homes and ground-level tours.
- Limit the seam between the two lenses can show on nearby objects. Keep important things away from the sides of the camera and use a thin tripod.
2. With a drone's spherical panorama mode
Many drones have a spherical panorama mode: the drone hovers in place and the camera takes several dozen photos, rotating and tilting row by row until it looks straight down. The app delivers a stitched sphere and also saves the original photos on the memory card.
- For quick results the sphere the app assembles works fine.
- For the best quality it's better to stitch the original photos in specialized software like PTGui, which lets you control the seams, the horizon and the exposure.
It's the foundation of a 360 drone tour for land subdivisions: from the air you can see the whole property, the surroundings and the location of each lot.
3. With a regular camera and a panoramic head
It's the highest-quality method for interiors and architectural photography. You use a DSLR or mirrorless camera with a wide-angle or fisheye lens, mounted on a panoramic head that rotates the camera around its nodal point: the point in the lens around which rotating produces no parallax.
If the camera rotates around a different point, near and far objects shift position from one photo to the next, and seams appear that the software can't stitch well. With the head properly calibrated, the photos stitch without errors even with furniture nearby.
It's common to shoot several exposures per position (bracketing) so the windows don't blow out and the corners don't end up dark.
4. With a 3D render
When the project doesn't exist yet, it's modeled in 3D and rendered directly in equirectangular format. In Blender, for example, it's done with the Cycles engine and a panoramic camera in equirectangular mode, with a 2:1 output resolution.
It's standard for off-plan sales: the buyer walks through the finished house or amenity area before it's built. They can also be combined: a real drone panorama of the land with the project drawn or modeled on top.
Common mistakes before publishing
- Visible seams. Lines or cuts where the photos join, especially on nearby objects. They're fixed by stitching again with more control points or by repeating the shot with a better rotation.
- Tilted horizon. In the tour it feels as if the world were leaning. All stitching programs let you level it before exporting.
- The drone or tripod on the ground. At the bottom you're left with the tripod, the photographer's shadow or a blurry area. It's covered with a patch or a logo applied over the sphere.
- Objects that moved. People or cars that appear cut off or duplicated because they moved between photos. You pick the photos where they aren't there or wait for them to pass.
- A ratio that isn't 2:1. If the image was cropped or exported at another size, the viewer stretches it. Always check that the width is exactly twice the height.
- Different exposure between points. If one panorama is brighter than the next, the tour feels choppy. Adjust color and light for all of them together.
Metadata: why it sometimes doesn't display in 360
Besides the pixels, a panorama can carry information inside that says "this photo is a sphere." The most widely used standard is Google's Photo Sphere, which stores data such as the projection type (equirectangular) and the size of the full sphere.
Platforms that display 360 photos rely on that data to know they should open it as a sphere. If you lose it while editing or exporting, the photo will look flat. Stitching programs and 360 cameras write it automatically; if you edit the image afterward, check that the program preserves it.
Inside a tour built in tour software or a web viewer it isn't needed: there, each image is already marked as a panorama.
Equirectangular or cubemap
A cubemap stores the same sphere as six square faces: front, back, left, right, top and bottom. There's no stretching on any face, which is why some viewers and 3D engines prefer it.
In practice, equirectangular is the exchange format: it's what cameras, drones and stitching programs deliver, and what every tour program accepts. If a viewer needs a cubemap, it converts it internally.
How it's published on the web
A browser on its own shows the equirectangular image flat. To move around in it you need a 360 viewer, which projects it onto a sphere and lets you turn the view with a finger or the mouse. There are open-source options like Photo Sphere Viewer and full tour-building programs like 3DVista.
For it to load well:
- Export as JPG or WebP with medium or high compression. The quality difference is barely noticeable on the sphere and the file size drops a lot.
- Use tiled loading if the panorama is very large, so the phone doesn't have to download all of it before showing it.
- Load a light version first and then the detailed one, so the user doesn't see a blank screen.
What it's used for in a real estate project
In project sales, the equirectangular image is the raw material for several pieces:
- The 360 tour of the land, taken with a drone, so someone who lives in another city understands where the project is and what's around it.
- The interior tour of a model home or an apartment.
- 360 renders of what doesn't exist yet: the finished house, the amenity area, the access road.
- The lot layout over the panorama, so each buyer can find their lot on the actual land.
On its own, a panorama shows the place. To sell, it's combined with information that changes: which lots are available and how to request more details. That's the part that connects the tour with the interactive masterplan and with how to show lot availability on your website.
If you want to build your own tour from scratch, this step-by-step guide to making a real estate 360 virtual tour (in Spanish) covers the full process, from capture to publishing.
How we do it at Royaltor360
At Royaltor360 we capture the panoramas with a drone on site, stitch and retouch them, and build the 360 tour with the lot layout on top. The tour connects to the interactive masterplan and a CRM, so the availability the buyer sees is the same one the sales team records. You can watch the 1-minute demo.