https://mappendix.com/GPX_IMAGE/v1

This is a placeholder for an XML namespace.

It is an extension to the GPX format that adds images.

The usage is as follows:

<gpx xmlns="http://www.topografix.com/GPX/1/1"
     xmlns:img="https://mappendix.com/GPX_IMAGE/v1">

<wpt>
  <extensions>
    <img:img src="https://example.com/images/IMG_1234.jpg"/>
  </extensions>
</wpt>


Images can be added to waypoints, routes, tracks, route points, 
track points, and to the file's root metadata element. Those 
elements may have multiple images.

The syntax of the <img> element is supposed to match the HTML <img> 
element.

Supported URL schemes and image file formats are independent of this 
specification, but possibilities include https: to link to internet 
resources and data: to embed the image within the GPX file itself.

The following URL scheme is described for additional information:

applephcloudidentifier URL scheme
---------------------------------

See https://developer.apple.com/documentation/photokit/phcloudidentifier

A PHCloudIdentifier is a persistent identifier string for a photo in an 
iOS / macOS user's photo library, including cloud photos.

This URL scheme wraps that identifier. The raw string is URL-encoded 
(aka "percent escaped") and prefixed with the scheme. Example:

  applephcloudidentifier:32A01DD9-75DF-41B2-8773-80C153D73A5A%3a001%3aAQohY6yKZR0%2btXlMi9FUQ82zySGo

(Note that a previous version of this document wrongly suggested that the 
scheme and data should be separated by "://", rather than ":". Applications 
parsing these URLs should consider accepting both.)