[Tagging] Survey points

[Malcolm Herring]

The Wiki is very clear (in several languages) as what a survey point is, 
but is there some other meaning that mappers understand this term to 
mean? The reason I ask is that I often come across man_made=survey_point 
tags that have been added to other objects. Not infrequently this tag 
replaces an existing man_made=* tag, even though other tags describing 
the original object remain. This then creates a nonsensical set of tags. 
I have just come across these tags added to some buoys in the middle of 
the River Maas! As is often the case, the changeset was un-commented, so 
I have added a query comment to see if I can discover what was in that 
mappers mind.