Throughout the web app, our mobile app, our website, socials, forum, etc. you may see the same vocabulary repeatedly frequently. Some of these terms have been coined by the Mapillary team, and thus need to be defined! 

 

Mapillary-defined terms:

Image key

Every image on Mapillary gets assigned a unique key distinguishing it from other images. This key is present in the URL when viewing an image on the web, in the snippet "pKey=IMAGEKEY" (potentially between ampersands (&)).

You can also find the image key when you click on the three dots icon (...) at the bottom right of the viewer and open the "Advanced" section

If you have the key of an image and want to view it on the web, use the following shortcut URL: https://www.mapillary.com/app/?pKey=[IMAGEKEY]

 

Sequence key

The images on Mapillary are arranged into sequences based on when they were captured/uploaded by a user. Each image is assigned a sequence key to link it back to their parent sequence.

You can find the sequence key when you click on the three dots icon (...) at the bottom right of the viewer and choose Advanced Options. 

 

Spatial arrows

The spatial arrows are displayed at the bottom center of an image and enable you to “look around” among the total pool of images around a particular place.

Spatial arrows find the best next matching image in the area, regardless of who has contributed it. The image is not necessarily in the same sequence as the one you are currently viewing (as it is when you use sequence arrows).

Spatial arrows might skip images if they are too close, or disappear altogether when there’s no image close enough to make the transition between the two smooth enough.

 

Playback arrows

Playback arrows are seen at the top center when looking at an image on Mapillary. Use these to automatically play up or manually browse through a capture.

Browsing through a capture with playback arrows replicates the track of the person who captured it. That means that you will not be able to “look around” among all the images at the particular place like you can with spatial arrows.

 

Other definitions to know:

EXIF

Exchangeable image file format, a standard for storing data in images. This can be thought of as image metadata: annotating the location, timestamp, type of device used to capture the image, and more. Typical cameras (including smartphones) save EXIF data automatically, but the specifics depend on the device—for instance, the device needs to have GPS in order to write location information into the EXIF data upon capture. There are programs that enable to add information to EXIF post-capture (e.g. add geotags to images).

To upload an image to Mapillary, the minimal information required in the EXIF data is the GPS position and the capture time of the images.

• GPS position—both GPS GPSLongitude and GPS GPSLongitude are required.
• Capture time—one of the following fields is required: EXIF DateTimeOriginal, EXIF DateTimeDigitized, EXIF DateTime, or GPS GPSDate.

You can see some technical documentation about editing the EXIF field here.

 

It might be useful to know that the Mapillary mobile apps normally only write EXIF information to the images during upload or during transfer from an external camera—not at the time of capture. (In iOS, there is also a special button for writing the EXIF information without uploading.) Also, the Mapillary mobile apps write GPS information into the ImageDescription field and the Mapillary system will prefer that to the GPSLongitude and GPSLatitude fields.

Therefore, if you export the images from your phone in a manner that adds EXIF data, and edit their location information by modifying the GPSLongitude and GPSLatitude fields, these edits will not be seen on the Mapillary database since it will still read the GPS data from the ImageDescription field.

To avoid writing any location information into the ImageDescription field, you need to copy the images you've captured via the mobile app straight from your phone or camera's memory, without transferring or adding EXIF data. That way you can edit the GPSLongitude and GPSLatitude fields (either manually or from a recorded GPX track) in a way that lets them be recognized by the Mapillary system.

 

GPS

a.k.a. the Global Positioning System. GPS is a global navigation system that provides geolocation and time information under the condition that there is an unobstructed line of sight to four or more satellites. Most cameras used to contribute to Mapillary have a GPS unit innate to them, however certain cameras do not and may need to be used in conjunction with a separate GPS unit. In the latter case, you can use tools such as computer programs or scripts to write the GPS information from the recorded track to the image EXIF data. Remember, the better the GPS accuracy, the better the positioning on Mapillary!

 

Panorama

A panorama is a 360° image. We have panorama support in the Mapillary viewer (use your mouse to pan around).

For an image to function as a panorama on Mapillary, it must be equirectangular (2:1 aspect ratio) or contain GPano Photo Sphere Metadata. 

If the resolution doesn't correspond to a full 360x180 panorama, Mapillary will treat this like all other images. With some cameras, it's just a matter of a few pixels and you might be able to fix it by adding some padding to the images before you upload. (Note that this also works the other way: if your regular image is so wide that it corresponds to the 2:1 ratio, it will be rendered as a panorama on our platform.)

The Mapillary mobile apps don't capture stitched panoramas. You can still get a panoramic view by just capturing a sequence of photos with lots of overlap. Once uploaded, you can use navigation arrows to "look around" with smooth transitions that enable a nice 360° view of the surrounding, even though the images have not been actually stitched together.