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Google Street View Photography Virtual Tour Visual Storytelling

What is a photosphere?

A photosphere is a panoramic image that covers 360 degrees horizontal and 180 degrees vertical. In other words, it covers an entire sphere, which is where it got its name.

But the real question is how is it created? Images are shot with a camera on a special mount made specifically for the task. The details of how the mount works are very technical. If you’re interested in exploring them, here is a good article: Entrance Pupil Alignment. Using the special mount, four or more overlapping images are captured. The number of images varies depending on the lens used and the resolution required for the final image.

Images required to assemble photosphere

Capturing the images

These eight images where shot in two rows of four. Each image overlaps four other images. I also use a technique called HDR for capturing the dynamic range of the scene as explained in my previous blog. I take eight positions with five images each for a total of 40 images. The 40 images are fed into PTGui, which is a panoramic stitching program used to assemble the images. The resulting image is called an equirectangular projection and it has an aspect ratio of 2:1 or 360:180 degrees.

Resulting image from the 40 images

Stitching the images together

The bottom of the image includes an area that was obscured by the camera head and tripod. I bring the image into the program Pano 2 VR where a patch for the area lost to the tripod is cut out. A replacement image is created in Photoshop and used to replace the patch. There is also an option for creating a mirror ball that reflects the image onto a sphere.

Equirectangular image with nadar patch

You can see in this image that the brickwork has been cloned in. The image is ready for publishing.


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Creating the tour

This isn’t the end of creating a virtual tour. Once all the images have been uploaded to the server, they need to be connected and placed in their proper position on Earth. The moderation process is a science in itself. Each image is moved and rotated until it lines up. This ensures that the perspective doesn’t change as viewers move from one photosphere to another. For quality control, Google inspects each tour. If all the requirements are not met, the tour is removed from public viewing until the errors are fixed. This is one of the reasons why you need to be a hire a Google Trusted Photographer. Google wants the photographers who create virtual tours to be trained and capable of creating tours that the public and business owners will enjoy without any intervention required on the part of Google. Yes, you can get photospheres shot and hosted on other sites. But why not put your business in front of Google Maps users by working with a Google Trusted Photographer like Story In Focus?