Some of you may already use the daily and weekly change view of Opensnowmap.org to check for changes on the ski pistes they mapped.
Today, this view have been improved and now gives more information about the actual change. Is this a way, a relation deleted, a simple node moved? A new processing associated with a detailed legend will help to better understand thechanges and maybe spot errors.
See, yesterday apparently someone seems to have refined a nicely mapped skating ring.
This view coupled with the 
button will allow you to find more information about the modified element. It is still a bit frustrating not to be able to check on deleted elements, I will try to add daily and weekly .html change list to allow this.
In practice, each night, the pistes of the OpenStreetMap database at 00:00GMT are compared to the pistes that were there the day and the week before. Geometries are simplified in order not to display to much information.